home Interpreter 1 what methods of sensory analysis are called analytical. Distinctive Sensory Evaluation Methods: A Group of Quantitative Methods

1 what methods of sensory analysis are called analytical. Distinctive Sensory Evaluation Methods: A Group of Quantitative Methods

Who can be a better assistant in the development of a new product than the consumer himself? Meanwhile, he is not considered by marketers as a real partner, usually his participation is reduced only to the role of a judge and evaluator of what is offered by the manufacturing company. However, in our opinion, the R&D department (R&D - research and development, the process of research and development of new products. In Russia, such departments are sometimes called the "department of new developments", R&D, research center, etc.) it is imperative to listen to the voice of the consumer throughout throughout the product development cycle. In this case, his opinion and perception can directly influence the process of creating and modifying new products. With this approach, the developer, having constant feedback from the consumer, knows how well the prototypes meet the needs and expectations. target audience(See Fig. 1).

Then the participation of the end user in the creation of new products becomes part of the formal procedures and business processes of the developer company. There is even a scientific discipline that can help in their development - Consumer science (the science that studies the behavior of consumers and households in communication with the market, market institutions, products, etc. It is located at the intersection of such disciplines as sociology, psychology, business). It is not so easy to give it a clear definition, because its various elements are dealt with in the food industry, and psychology, as well as sociology and economics.

In this case, we will focus on consumer science to the extent that it is designed to help R&D departments in creating new products or modify existing products. In the field of product development, these professionals (also known as consumer & sensory researchers) are experts who work hand in hand with flavor specialists, formulators, engineers, designers, and so on. Thus, the researcher must not only be a sensory expert - he must be competent in detail in his knowledge of the main driving forces in the dynamics of the products he is working on: for example, drinks, confectionery, dairy products, wine, etc.

The "sensory explorer" has a set of methods and procedures that can be used to help product developers create a better product. But before they get down to business, it is necessary to define business tasks and research goals and agree on them among themselves. When it is clear that customer acceptance is critical to the product development process, then affective testing is indispensable.

Emotional testing

Emotional testing (see Stone & Sidel, 2004) usually refers to either a pairwise comparison test or an assessment of a new product on a 9-point scale of like-dislike (overall liking). This 9-point scale (see Figure 2) is more useful when testing many products and/or prototypes, and is often used in product development to have an understanding of how things are progressing. research projects. There are standardized procedures for making decisions based on test results.

Rice. 2: 9-point rating scale (check only one option)

Decision standard

A decision standard is a statistically valid process for determining the success of a sample. In a simplified form, it can be formulated as follows: "the prototype should receive a significantly higher average score on the overall attractiveness parameter than the standard (reference) sample, with a confidence interval of 95%". The standard could be some trademark, current product, "gold standard", etc. The decision standard can be quite complex when there are several reference products to consider when comparing, other parameters (eg relevancy) and key characteristics (eg bitter taste). The decision standard is recommended only as a guide in the early stages of the product development process, since at this stage the purpose of the study is to study and general understanding of the situation, and not to evaluate a new product based on success criteria.

recruiting principles

It may seem easy to define your target customer profile when you have a well-defined business goal, but very often this is not the case. The business goal could be a new brand, a product line extension, an updated brand, a new product variety, etc. Each of these business objectives may require different customer groups. Thus, the recruitment of respondents participating in the study must correspond to a specific business goal each time. For example, a brand renewal project may require, at a minimum, current users brand and possibly "switching" consumers, ie. disloyal brand users. I've heard a lot of stories about studies where the selection parameters were: " women, 18-55 years old, live"Joke a joke, but such an approach would be a real disaster for most research programs that are trying to provide support for risky business decisions.

In addition, it should be kept in mind that much of the variability within and between studies is caused by the variability of the consumers themselves. If we observe significant differences in standard sample scores from test to test, then the recruitment method may well be the cause.

Respondent types

Inexperienced Buyers/Testers (naive consumers/acessors) - as a rule, these are people who have not participated in consumer / marketing research within the last 6 months. However, in modern reality, when testing has become a fairly widespread phenomenon, a period of non-participation of 3 months looks like a more realistic figure. Other derogations and exceptions depend on the particular study. Usually, the naive consumer demonstrates honest emotional reactions to general and specific characteristics of the product.

Experienced Buyers/Testers (experienced consumers/acessors) are those who have repeatedly been involved in various consumer research and become an “experienced” test participant. Typically, these consumers are recruited from a small, cost-effective database that sooner or later suffers from overuse. The ratings of such consumers are based not on their real personal preferences, but on the previous experience of participating in testing. They cannot be considered typical consumers. As my personal observations show, savvy/professional consumers are not good at differentiating between tested products - i.e. the final test data does not make it possible to identify differences between products.

Trained touch panelists (trained sensory panelists) are test takers who are specially trained to use an analytical approach in evaluating a product and, therefore, their information is different from consumer information. Specially trained participants are also called trained respondents or assessors. They have received special training in sensory analysis, which provides a quantitative description of products. Thus trained participants do not—and should not—give an emotional response in their assessments.

Employees (representatives of the industry, companies) — this is a category to be avoided at all costs when conducting any emotional tests. Most likely, these people are not your target customers, they are too well informed, and sooner or later their participation will become too frequent.

Selection of respondents

Of course, the screener plays a decisive role in choosing a respondent, i.e. a preliminary questionnaire used to determine whether a consumer is eligible to participate in a study. Filling it out should take no more than 5-10 minutes. The screening questionnaire is built on all criteria of research tasks and business goals.

Great importance screener is that it screens out potential threats to your study, such as participation in past studies (eg, experienced consumers), safety (eg, a professional in this field), the presence of diseases (eg, a cold), the presence of food allergies (for example, for dairy products), failure to participate in testing (for example, lack of smell), and/or failure to complete the study (for example, availability for the entire period of testing).

The more selection criteria you include in the screener, the more expensive recruiting becomes, but the more likely you are to find members of the target audience, and the more homogeneous the composition of the participants will be. For example, if you need

(a) mothers (18-35 years old),
(b) with the first child (0-18 months),
(c) who were married less than 5 years ago,
(d) use a certain brand of baby food,
(e) purchased from certain types of stores,
then, it is clear that you are recruiting a very homogeneous group of respondents of a narrow consumer segment. And it is also clear that such a recruit will cost a lot.

Questionnaire

In quantitative research, the questionnaire is the main means of communication with the consumer. In order to obtain effective feedback from consumers, the structure of the questionnaire, the questions asked, and the order and manner in which questions are asked are critical. However, there is significant diversity between different companies, research providers, and different projects within the same company.

The consumer questionnaire usually contains questions on the evaluation of the general parameters of the product (attractiveness, purchase intentions, relevance), diagnostics (the product is exactly what it is needed), product characteristics (descriptors/attributes), virtues (satisfies the need), and also on the just experienced / emotional perception (pleasant). Since the product has many characteristics/attributes, the questionnaire should focus on the most relevant issues.

Study Design

When testing two or more products, the sequential monadic test is most often used. In this approach, each respondent evaluates several products, but not necessarily all. The order in which each product is rated is randomly assigned to each respondent - with the products shown on an equal footing. If for some reason too many products need to be tested in one session, then there are more complex techniques for this, for example, the method of balanced incomplete block diagrams (BIB - Balanced Incomplete Block Design, Cochran and Cox, 1957), in which not all products are evaluated by all respondents.

The intended goals of consumer testing in product development are to generate new information and to ensure that the study is replicable. Therefore, the sample size is usually smaller (100≥N≥75 and sometimes less per tested product) than in marketing research. However, the sample size should be sufficient to make the necessary changes in the direction of the study.

The testing procedure should be adjusted to suit the requirements of the particular study. For example, the type of product (Jalapeño versus tomato sauce) may limit the number of samples that can be evaluated in a single test session. In addition, factors such as the amount of sufficient serving to serve one test taker, the length of the test, and many other factors must be considered. When developing a test protocol, it is important to avoid such a serious problem as respondent fatigue - for example, it can be sensory, psychological or physical.

Where to test

In principle, the product developer has the opportunity to conduct practical testing in natural conditions (In-Use Test) or testing in a special research room (Central Location Test - CLT). Both of these options are valid for holding in different cities or countries. When choosing a particular method, many factors should be considered:

timing
staffing
type of product being tested
number of prototypes to test
the resources needed to produce each prototype in a given quantity
how many times prototypes will be tested
applicable best practice
corporate culture
real conditions of consumption, etc.

Practical testing (In-Use Test) (for example, at home, in a car, in a restaurant, etc.), as a rule, is carried out at home and is called the Test in the household (Home Use Test - HUT). The HUT option is less comfortable for product developers than CLT. It generally takes longer than CLT, more respondents (and therefore more expensive), and requires more products to test. However, the choice to use HUT in product development can be strongly dictated by corporate culture, such as the requirement to use HUT over CLT wherever possible.

The CLT test is usually carried out in a room specially designated for such studies and is adapted to the study of a wide variety of products. However, regardless of where you conduct your testing, the environment for it should be appropriate for the products being evaluated.

Statistical analysis

In studies with more than two products, Analysis of Variance (ANOVA) is used to evaluate different prototypes against each other and (where applicable) against the reference(s). At the very beginning of the product development process, the sensor specialist is more concerned with product improvement directions than with statistical differences.

How it's done

If for you the consumer becomes an obligatory partner in your work, and the process of developing and optimizing the product becomes repeated many times, then you can select several iterations from time to time. As a rule, the ultimate goal of the work is to make the product more popular and increase its marketing characteristics such as overall attractiveness (overall liking), product credibility (believability), intention to buy the product (buying intention), etc. But how can this be achieved? General rule- when creating prototypes should adhere to regularity.

There was a certain specific version of chips, which, literally and figuratively, became boring to consumers and began to yield to its competitors in the market. Therefore, it was necessary to breathe new life into it. To develop a screening questionnaire, the necessary audience data was obtained from the client's marketing department. The overall goal in product development is to provide improved potato chips that can successfully compete with other products.

At the initial stage, it is necessary to determine the problematic aspects of the existing product variant using a comparative study (with the participation of a benchmark - a competitor's product). At this stage, the existing option is studied along with the products of competitors and, possibly, some "estimations", preliminary ideas. It is assumed that (as often happens) the marketing department has already analyzed these aspects and already has some suggestions for product development. The questionnaire focuses on the aspects most relevant to consumers. Sensory data is focused on specific product characteristics.

A small benchmark study will enable us to profile the customer's product formula under investigation as well as competitors, and allow us to test four of the best guesses. Figure 3 (see Greenacre & Blasius, 2006) shows the results of this study. It can be seen that the existing option has the following aspects of consumer perception:

"traditional",
"habitual",
"simple taste"
"Still the same without change."

Sensory aspects of perception: "salty" and "fat". Now there are some clear guidelines for more systematic prototyping.

Figure 3: Map of perception of prototypes in a comparative study.

The number in front of each product represents the percentage of respondents who scored the top three ratings on the attractiveness scale. Consumer attributes are shown in black. Sensory attributes are indicated in white. Red attributes refer to emotions

Figure 4 shows the sequence of two additional studies. The attribute "naturalness" was a predetermined goal of the study, its guideline. After that, changes were made with more sophisticated approaches, primarily in the design of experiments. A sequence of two additional studies based on the initial combination of aspects of prototypes 1 and 4 is shown.

Summary

In general, the sensory researcher is concerned with translating aspects of product development into the consumer language and back-translating from the consumer language into the developer's lexicon. You can achieve your goals faster if the consumer acts as your partner, and product development is based on a planned approach. Because these product development studies are repetitive, they use small sample sizes. Recruiting target customers is essential to get spontaneous emotional responses. Only with this approach can one be sure that the final study, which should confirm or refute the changes in the product made on the basis of previous iterations, will not bring unexpected surprises.

Literature

Cochran, W.G. & Cox, G.M. (1957) Experimental Designs, 2nd edn. Wiley Classics Library Edition published 1992.

Stone, H and Sidel, JL (2004) Sensory Evaluation Practices, 3rd edn. London/New York: Academic Press/Elsevier.

Greenacre, M and Blasius, J (eds) (2006) Multiple Correspondence Analysis and Related Methods. Boca Raton, FL: Chapman and Hall/CRC.

EDUCATION AND SCIENCE

SENSOR ANALYSIS AS A COMPONENT OF COMMERCIAL EXAMINATION OF FOOD PRODUCTS

Rodina Tamara Grigorievna

Doctor of Technical Sciences, Professor of the Department of Commodity Science and Commodity Expertise of the PRUE G. V. Plekhanov. Address: Plekhanov Russian University of Economics, 117997, Moscow, Stremyanny per., 36. E-mail: [email protected]

Discussed state of the art sensory analysis food products at the domestic and global levels. The developments of the Department of Commodity Science and Commodity Expertise in the formulation of the educational process of the discipline "Sensory Analysis of Food Products" for the training of specialists and bachelors in the direction of "Commodity Science" are briefly outlined. The information is given in comparison with foreign experience in testing and training tasters in accordance with the recommendations of CAC / GL 31 - 1999 "Codex Guidelines for the Sensory Evaluation of Fish and Shellfish in Laboratories".

Key words: organoleptic science, ISO and FAO standards, Codex Alimentarius, testing and training of specialists and bachelors in the field of organoleptics.

SENSORY ANALYSIS AS A COMPONENT OF COMMODITY EXPERTISE OF FOOD PRODUCTS

Rodina, Tamara G.

Doctor of Technical, Professor of the Department of Commodity Research and Commodity Expertise of the PRUE.

Address: Plekhanov Russian University of Economics, 36 Stremyanny Lane, Moscow, 117997, Russian Federation. Email: [email protected]

The article discusses the current state of the sensory analysis of food products at the domestic and worldwide levels. It summarizes the recearches of the department of commodity research and commodity expertsis in the formulation of the educational process of discipline "Sensory analysis of food products" for the training specialists and bachelors in "Commodity". Information is given in comparison with foreign experience of testing and training tasters in accordance with the recommendations CAC/GL 31 -1999. "Codex Guidelines for the Sensory Evaluation of Fish and Shellfish in Laboratories".

Keywords: science of organoleptics, ISO and FAO standards, Codex Alimentarius, testing and training the bachelors in the sphere of organoleptics.

Product quality is determined by a set of properties that determine its suitability to satisfy certain human needs in accordance with the purpose. To assess consumer merits food products sensory or organoleptic methods based on the analysis of the sensations of the human senses are widely used.

In foreign and domestic literature, the terms "organoleptic evaluation", "sensory" or "organoleptic" analysis are often used as equivalent. The modern level of development of the science of organoleptics requires the separation of these concepts. Under the organoleptic assessment of the quality of food and taste products are understood general methods of assessment, in which information about the quality of products is perceived through the human senses. Organoleptic analysis is based on the application of scientifically based methods and conditions that guarantee the accuracy and reproducibility of the results. The term "sensory" is recommended to apply to the human senses. The concept of "organoleptic" is of Greek origin, the words "sensory" and "taster" have a Latin basis.

In a typical system of quality indicators, the place of sensory characteristics is determined in the group of ergonomic indicators that characterize the product-consumer-environment system and include hygienic, anthropometric, physiological, psychophysiological and psychological indicators. Psychophysiological indicators characterize the perception of the product with the help of the senses: sight, touch, smell, taste, sometimes hearing, as well as strength and other physical abilities of a person. These indicators are also called psychophysical, sensory or organoleptic. When determining the value of the indicator, the threshold ability of a person to perceive smell, taste, and tactile (tactile) sensations is taken into account. Sensory metrics, along with psychological metrics, make up the emotional value of a product.

In the second half of the twentieth century. the science of organoleptics was formed, which studies, with the help of human sensory analyzers, the consumer properties of food products, as well as food ingredients and intermediate forms of products.

A great contribution to the development of organoleptics was made by the Polish scientists D. E. Tilgner, N. B. Barilko-Pikelna, Soviet researchers G. L. Solntseva, R. V. Golovnya, T. M. Safronova, etc., G. A. Vuks in Estonia, a number of such foreign scientists as A. Coan, R. Molinag, A. Szczesniak, S. Roscher, M. I. McDanie1 and others. Scientific developments in the field of organoleptics are carried out by Russian scientists V. M. Kantere,

M. A. Matison, E. A. Smirnova, A. V. Ryzhakova, M. A. Polozhishnikova and others. Their developments are effectively used in the creation of new products, food additives, including flavor intensifiers, as well as to predict markets sales of goods in assessing the acceptability of new products, flavors, non-traditional forms of food for the population.

The development of organoleptics is at the intersection of the sciences of psychology, physiology, chemistry, physics, mathematics, technology, commodity science. At present, the country has formed and operates scientific centers methodology, standardization of organoleptics and methods of preparation of tasters.

Priority developments in the field of organoleptic analysis were carried out at the All-Russian Research Institute of the Meat Industry, the Institute of Food Substances, the Dalrybvtuz, the Plekhanov Russian Academy of Economics and a number of other organizations. The development of sensory methods is primarily necessary for merchandisers, whose main function is to study issues related to the quality of consumer goods. Technological food sciences are also in dire need of express analyzes of the organoleptic properties of food ingredients and finished products.

Organoleptic evaluation is the most ancient way to determine the quality of food products. The existing methods of laboratory analysis are more complex than the methods of organoleptic evaluation, they are laborious and make it possible to characterize mainly particular features of the quality of products. The organoleptic method quickly and with the correct formulation of the analysis objectively and reliably gives an overall impression of the quality of the product.

Scientifically organized organoleptic analysis surpasses many methods of laboratory research in sensitivity, especially in relation to such indicators as taste, smell, texture of products. Errors in sensory analysis most often occur with an unprofessional approach to this method of assessing food quality. The existing opinion about the subjectivity and irreproducibility of organoleptic assessments is mainly due to the fact that the individual characteristics of people are not taken into account, they are not specially trained and trained in sensory analysis techniques, the basic rules and conditions of a scientifically based organoleptic method for assessing food quality are not met, in particular, tasters are tested for sensory sensitivity, the requirements for the room in which the tasting assessment is carried out are not met, due attention is not paid to the choice of assessment method. The last circumstance is one of

most important for obtaining reliable and comparable results.

The current level of research in the field of commodity science of food products is unthinkable without sensory analysis, carried out using scientifically based methods. The methodology of sensory analysis, recommended for the selection of tasters and the examination of food quality, is contained in international ISO standards, among which the most significant in authentic Russian translations are accepted as national standards. Russian Federation, in particular:

GOST R ISO 5492-2005 “Organoleptic analysis. Vocabulary";

GOST R ISO 3972-2005 “Organoleptic analysis. Methodology for the study of taste sensitivity”;

GOST R ISO 5496-2005 “Organoleptic analysis. Methodology for training testers in the detection and recognition of odors”;

GOST R ISO 8586-1-2008 “Organoleptic analysis. General guidelines for the selection, training of assessors and control of assessors. Part 1. Selected testers”;

GOST R ISO 8586-2-2008 “Organoleptic analysis. General guidelines for the selection, training of testers and control over their activities. Part 2. Sensory Evaluation Experts”;

GOST R ISO 8588-2008 “Organoleptic analysis. Methodology. Tests "A" - "not A"";

GOST R ISO 8589-2005 “Organoleptic analysis. Research Room Design Guide”;

GOST R ISO 53159-2008 “Organoleptic analysis. Methodology. Triangle Method";

GOST R ISO 53161-2008 “Organoleptic analysis. Methodology. Pair comparison method.

ISO standards are of a general methodological nature. Much slower is the development of scientifically based harmonized methods for homogeneous food groups. Only two complex groups of fish products and invertebrates, in the examination of the quality of which, and above all freshness, sensory analysis is of decisive importance, are provided with the FAO CAC / GL 31 -1999 standard included in the “Codex Alimentarius. Fish and Fishery Product»1.

The Codex Alimentarius also introduces the concept of points of production deficiency (TNP), i.e. critical moments at all stages of production.

1 CAC/GL 31 - 1999 - Codex Guidelines for the Sensory Evaluation of Fish and Shellfish in Laboratories // Codex Alimentarius. Fish and fishery product = Codex Alimentarius. Fish and fish products / scientific ed. T. G. Motherland. - M.: LLC Publishing house "Ves Mir", 2007. - S. 167-198.

management of products that are not directly related to the risk factor for humans, but adversely affect the consumer properties by which the buyer evaluates the quality of the product: appearance, including packaging, flavor properties, texture characteristics and other sensory quality attributes.

From the point of view of TNP, the Codex Alimentarius pays the main attention to oxidative processes occurring in fish oils, especially from ocean fisheries, deterioration of the product texture due to the development of deep denaturation processes in the protein component of fish products, mechanical contaminants (foreign impurities) that can enter products in case of violations of sanitary control .

FAO CAC/GL 31 - 1999 Codex Guidelines for the Sensory Evaluation of Fish and Shellfish in Laboratories. Guidelines for Sensory Evaluation of Fish and Invertebrates in Laboratories" offers the following algorithm for the tester's actions in the sensory evaluation of products:

In frozen fish, the nature and condition of the packaging and glaze, the degree and depth of dehydration, discoloration are assessed, traces of previous defrosting and re-freezing are noted. The evaluation is carried out for fish in a frozen state and after thawing. It is noted that determining the freshness of thawed whole fish by appearance is not easy, since the process of freezing and thawing affects the characteristic features of fresh fish, such as eyes, skin, and the color of gills and blood. The gills have a leathery or slightly rancid odor even after short-term storage in a frozen state, which does not significantly affect the quality of the product.

In the event that a final decision regarding the odor or gelatinous state of the texture cannot be made after examining

following a thawed raw sample, a portion (approximately 200 g) is removed from it and immediately carried out heat treatment one of the recommended methods, as well as an assessment of smell and taste.

Particular attention in the standard is given to the selection and training of tasters. Objective sensory analysis of fish and products derived from fish and invertebrates requires the selection of experts for their ability to solve problems, as well as training them in the use of testing methods and monitoring the development of their ability to perform sensory analysis. Thus, training in organoleptic analysis includes:

The selection of tasters based on the basic intensity of sensations and the ability to describe these sensations objectively, i.e. without taking into account personal preferences. Allergy to seafood and nutritional supplements serves as a basis for excluding volunteers from candidates for tasters;

Development of sensory abilities by mastering testing techniques, improving the ability to identify organoleptic characteristics in complex food systems, as well as improving sensitivity and sensory memory in order to conduct accurate and reproducible sensory analysis of products;

Control over the actions of tasters and the stability of their work through periodic testing of sensory abilities.

To be included in the group of expert tasters, the candidate must demonstrate the following abilities:

Absence of anosmia, i.e., correct perception of odors - for the stable determination and description of odors of spoilage and other product defects;

Lack of ageusia, i.e., correct perception of basic tastes - for a stable definition and description of the types of taste characteristic of spoilage and other product defects;

Normal color discrimination ability, i.e., to determine anomalies in the appearance of fish, fish products and seafood;

Describe sensory experiences appropriately;

Master the terminology of new or unfamiliar sensations (smells, tastes, external signs and textures)

Identify stimuli and compare with the causes that cause them.

The first five criteria can be measured through testing, the last ability is developed through special training on specific products.

When testing, it is advisable to repeat tests to determine the basic tastes and smells. It is important to make sure that

the test subject is tested on basic abilities, not on his reactions to an unfamiliar testing environment.

For each testing technique, new numerical codes and presentation sequences must be used. For example, when evaluating the ability to perceive basic tastes, one must take into account all the variety of tastes associated with defects or spoilage that the taster is able to perceive and describe. This requires the development of a certain basic ability to perceive basic tastes. When selecting and training a candidate, first of all, his ability to distinguish between bitter and sour tastes, recognition thresholds and their differentiation is taken into account, since these tastes are most important for the study of fish and fish products and invertebrates, as they appear in the early stages of putrefactive spoilage.

The standard deals with approaches to testing the olfactory, color discrimination, tactile ability of tasters. The CAC/GL 31 standard also pays attention to the training of assessors. The proposed plan of the discipline "Sensory research of fish and seafood" is designed for the duration of basic training sensory science from 10 hours to a full university course. Each section is expected to be followed by practical exercises to demonstrate the concepts discussed (for example, the preparation of basic flavor solutions and their sensory exploration of taste). Monitoring the effectiveness of training and the relevance of sensory conclusions is achieved through continuous monitoring of the conclusions drawn up by the trainees.

The standard gives the characteristics of such defects as signs of staleness, deep dehydration, “rust”, texture conditions, refrigerator odors, etc. A list of terminology is provided that defines the positive and negative characteristics of each sensory indicator. The sequence of sensory evaluation of cephalopods and crustaceans is considered, information is provided on approaches to the selection of samples for the training of testers, which are practiced in other countries, for example, in Canada. A list of lecture topics on the theoretical training of testers is also considered.

The Department of Commodity Science of Food Products (now the Department of Commodity Science and Commodity Expertise of the Plekhanov Russian University of Economics) has priority in setting up the educational process for the specialist and bachelor’s levels in the direction of “Commodity Science” and in developing

botke of educational and methodological support in the field of sensory analysis of food products1.

The following topics are considered in the educational process at the theoretical and practical level.

Theme "General information about the science of organoleptics." The objective of the topic is to teach students the terminology in the field of organoleptics and the use of normative documents international and domestic level on the standardization of sensory analysis.

As part of the study of the topic, an introduction to science is given. The definition of the science of organoleptics, its goals and objectives is given. The role of sensory analysis in the examination of the quality of food products. Basic conditions necessary to ensure objective and reproducible results in tasting analysis. The contribution of domestic and foreign scientists to the development of the science of organoleptics is considered. Prospects for the development of science. Information is given on the standardization of organoleptics and the conceptual apparatus.

Sensory characteristics are considered as a component of the quality of food products. A classification of quality features of food products is given: indicators of purpose, manufacturability, shelf life, aesthetic and others, as well as factors affecting quality. The place of organoleptic indicators in the system of qualitative characteristics of food products is determined. The nomenclature of indicators determined with the help of the sense organs and modern terminology are described.

At the present level, the nature of the substances that determine the color and flavor of products, the problem of colorants, flavors and flavorings in connection with the risk factor for human health are described. The influence of the structure, composition and properties of products on the indicators of consistency, density, elasticity and others, perceived with the help of deep touch (pressure) in the oral cavity, is described; the relationship of consistency with the characteristics of digestibility, freshness, deliciousness and other features that form general idea person about the quality of food products.

The theme "Psychophysiological foundations of organoleptics" aims to teach students how to select tasters for organoleptic analysis of food products, as well as the rules for processing test results.

1 Rodina T. G., Vuks G. A. Tasting analysis of products: a textbook for university students. - M. : Kolos, 1994; Rodina T. G. Sensory analysis of food products: a textbook for university students. - 2nd ed. - M.: Academy, 2006.

The content of the topic outlines the theoretical foundations for the perception of sensory features of goods. Are given general information about the anatomy and physiology of the organs of vision, taste, smell, touch. Modern concepts and classifications of tastes and smells are presented. The key and compositional nature of odors are described, physical properties and the chemical nature of substances perceived by the organs of taste and smell.

The theoretical foundations of the perception of color, taste, smell, influence external conditions and individual characteristics of tasters on the sensitivity of the organs of vision, taste, smell and touch. The concept of "language map", visual, gustatory and olfactory sensitivity (thresholds of perception, sensory memory, etc.), adaptation and fatigue of the sense organs, masking and compensation of tastes and smells, and other information necessary for organizing the correct work of expert tasters are given.

Observations of scientists on the influence of gender, age, genetic and other individual factors, geographical features, national traditions on the perception of sensory organs are noted.

Particular attention is paid to the issues of testing tasters in terms of sensory abilities, in particular, testing the visual, olfactory and taste sensitivity of tasters, testing the reproducibility of the results of tasting tests of product quality.

The domestic and foreign experience of testing tasters is presented. The problems of training expert tasters in connection with the need to improve the system of conformity assessment and examination of the quality of food products are considered.

The topic "Organization of modern sensory analysis" sets the task of developing students' skills as organizers in the field of modern sensory analysis of food products, able to create a sensory analysis laboratory and provide maximum assistance to its effective functioning.

The central place is given to the development of methods of tasting analysis. The systematization of methods is considered, the characteristics of consumer and analytical methods are given. The advantages and possibilities of methods for solving specific problems are outlined, as well as an assessment of the reliability of the results.

In the lecture part and in practical classes, special attention is paid to the prospects of the scoring and profile methods in the tasting examination of the quality of products, as well as in solving research problems.

The FAO/WHO standard discussed above does not provide for the use of descriptive analytical methods to assess product quality.

In the discipline "Sensory analysis of food products" the principles of constructing traditional scoring scales, the shortcomings and ways to improve the scoring system for assessing the quality of products are studied in detail; rules for the development of evidence-based point scales, taking into account modern requirements; the concepts of scale range (points), gradations of weight coefficients, etc. The requirements for the set of qualitative descriptions of the scale are presented: general use, unambiguity, distinguishability, sufficiency. Examples of evidence-based scales are given. The advantages of the points system are discussed.

Theoretical and practical aspects of the application of the profile method for the comparative characteristics of the quality of objects, stability in the storage of food products are considered. They are presented in lectures and mastered in the practical part of the rules for constructing profilograms.

In the section of the topic “The system of organizing and conducting sensory analysis”, the modern requirements for the premises and equipment for conducting organoleptic analysis are outlined. In accordance with the recommendations of the ISO and GOST R standards, conditions are determined regarding the premises, lighting, equipment, utensils, auxiliary materials and others that provide proper organization work of tasters to obtain objective and reproducible results. The sources of errors in the tasting analysis are highlighted from the standpoint of the working conditions of the taster.

Students are introduced to the organization of the work of the tasting commission, the algorithm of actions of the chairman and members of the team of tasters, the rules for submitting samples for tasting, coding samples, and processing results. The development of the functions of tasting commissions in the system of quality control of food products and from the standpoint of educating the tastes of consumers is discussed.

The topic "Expert methodology in tasting analysis" sets the task to teach students the methods of scoring scales and profile analysis used in organoleptic testing of food products, to teach the rules of working with expert tasters.

Perts in various operations that make up the process of modern tasting analysis (in choosing the nomenclature of product quality indicators, determining the weighting coefficients of indicators, selecting basic values of indicators, establishing criteria for certain categories of food quality); participation of expert tasters in evaluation operations. The requirements for the quality of expert tasters are outlined: competence, objectivity, conformity, etc.

Students are introduced to the procedure for training, testing and certification of expert tasters and tasters in the Register of the Personnel Certification System of the RSSP Rosstandart in the form of voluntary certification operating in Russia.

In the section "Expert Methods in Designing Scoring Scales and in Profile Analysis" students are introduced to the traditional scoring systems included in normative documentation, as well as applied in the practice of specialists and scientific research in Russia and abroad.

In the educational process, the rules for the development and testing of scientifically based scales for the sensory analysis of food products (using weight coefficients of quality indicators), as well as the algorithm for developing and discussing profilograms of sensory features of food products, are mastered. These descriptive methods of sensory analysis are effectively used by students when performing WRC.

The topic "Relationship between the results of sensory and instrumental analysis" has the task of teaching students the basic techniques for assessing the correlation coefficient and graphical representation of the relationship between the results of sensory and instrumental analysis. The content of the topic considers the relationship between the descriptive and qualimetric characteristics of sensory features with physicochemical and other quality indicators determined by instrumental methods, and discusses the problem of correlation between objective and subjective measurements. Examples of organoleptic and instrumental descriptions of indicators characterizing the quality of food products are given. An organoleptic assessment of the quality level is given using qualimetry techniques. Single and complex quality indicators are considered, the use of calculation and graphic methods for determining the relationship between the results of sensory and instrumental analysis, characterizing the taste properties of products, texture, consistency; examples of determining the correlation dependence.

For different profiles and levels of training (specialist or bachelor), the volume of the lecture part of the discipline varies within

from 16 to 28 hours. For the profiles "Commodity Management" and "Examination and evaluation of goods" the volume of lectures is reduced to 8 hours, and the discipline itself is combined with materials science, which causes significant damage to the educational process. In the practical part of the classes, students master the rules for testing tasters for sensory abilities and descriptive methods of sensory analysis, the development of a scientifically based scale (in the form of a business game), as well as the development and discussion of profilograms.

As a result of mastering this discipline, students form professional competencies (PC):

PC-3 - knows how to use regulatory and legal documents in their professional activities;

PC-5 - uses knowledge of the basic laws of natural sciences to ensure the quality and safety of consumer goods;

PC-6 - is able to apply knowledge in the field of natural sciences and applied engineering disciplines for the organization of trade and technological processes;

PC-13 - knows the range and consumer properties of goods, the factors that form and preserve their quality;

PC-14 - knows the methods of identification, assessment of the quality and safety of goods and uses them to diagnose defects, identify dangerous, low-quality, counterfeit and counterfeit products.

We have developed FOS for conducting boundary, current control of knowledge, as well as for controlling residual knowledge for intermediate certification and independent work students in the direction 100800 "Commodity Science", profiles: "Commodity Science and Expertise in the Sphere of Production and Circulation of Agricultural Raw Materials and Food Products" and "Commodity Science and Expertise in the Sphere of Production and Circulation of Agricultural Raw Materials and Non-Food Products", as well as profiles "Commodity Management" and “Commodity expertise and appraisal activity”.

Students actively use the scientific methods of sensory analysis in preparing the WRC. In dissertations, as a rule, much attention is paid to the sensory analysis of research objects, which effectively improves the quality of research.

Bibliography

1. Bodunkova T. S. Using a sensory profile analysis method for a comparative assessment of the quality of chocolate // Commodity researcher of food products. - 2011. - No. 3. - S. 18-22.

2. Kantere V. M. Basic methods of sensory evaluation of food / / food industry. - 2003. - No. 10. - S. 6-13.

3. Rodina T. G. On the issue of food security in Russia / / Fundamental research. - 2009. - No. 5. - S. 62-63.

4. Popov I. A. Prospects for tasting analysis in the quality control of fish and seafood / / Twenty-seventh International Plekhanov Readings. March 24-27, 2014: student abstracts: in 2 books. - Prince. 2. - M.: FGBOU VPO "PREU im. G. V. Plekhanov, 2014.

5. Ryzhakova A. V. A systematic approach to the sensory assessment of the quality of sweets / / Bulletin of the Russian Economic Academy named after G. V. Plekhanov. - 2007. - No. 2. - S. 105-112.

1. Bodunkova T. S. Ispol "zovanie sensornogo profil" nogo metoda analiza dlya sravnitel "noy otsenki kachestva shokolada, Tovaroved prodovoVstvennykh tovarov, 2011, No 3, pp. 18-22. (In Russ.).

2. Kantere V. M. Osnovnye metody sensornoy otsenki produktov pitaniya, Pishchevaya promyshlennost, 2003, No 10, pp. 6-13. (In Russ.).

3. Rodina T. G. K voprosu o prodovol "stvennoy bezopasnosti Rossii, FundamentaVnye issledovaniya, 2009, No 5, pp. 62-63. (In Russ.).

4. Popov I. A. Perspektivy degustatsionnogo analiza v kontrole kachestva ryby i moreproduktov, DvadtsaV sed "mye Mezhdunarodnye Plekhanovskie chteniya. March 24-27, 2014, tezisy dokladov studentov, v 2 kn., Kn. 2, Moscow, FGBOU VPO "REU im G. V. Plekhanova", 2014. (In Russ.).

5. Ryzhakova A. V. Sistemnyy podkhod k sensornoy otsenke kachestva konfet , Vestnik Rossiyskoy ekonomicheskoy akademii imeni G. V. Plekhanova, , 2007, No 2, pp. 105-112. (In Russ.).

URAL STATE ACADEMY

VETERINARY MEDICINE

Department of Commodity Science and Expertise of Food Products

Test

in sensory analysis

Troitsk, 2007

21. Distinctive methods of sensory analysis

Distinguishing Methodsqualitative analysis

When using this group of methods, before starting the tasting, it should be determined whether the application of the test is one-sided (when only one direction is of interest) or two-sided (when both directions are of equal interest).

Methods are used when the difference in organoleptic properties of two or more products is being investigated.

Pair comparison method.

The paired comparison method is used in the following cases:

When there are directional differences between the two test samples (for example, more and less sweet);

To establish whether there is a preference between two evaluated samples;

When training tasters: to select, train and control the abilities of trainees.

According to this method, paired samples must be submitted for evaluation simultaneously or sequentially. Pairs are made from samples with slight differences. In all pairs, the same samples are offered in random order, for example, AB, BA, AB, etc. Several pairs may be offered in a sequence (series of pairs) to reduce or completely avoid sensory fatigue, adaptation to the product being tested.

Depending on the purpose of the study, tasters may be asked the following questions:

a) a test to determine directional differences: "Which of the two samples is the most sweet (salty, bitter, fragrant, etc.)?"

b) Preference test: "Which of the two
of the presented samples do you prefer"?

c) Teaching tasters: "Which of the two presented samples is the most...?"

The method of conducting the analysis according to paragraph "b" "The test for determining preferences coincides with the above method of consumer assessment, therefore, one or another method is used based on the analytical goal.

When applying the procedure according to point "a", the taster is obliged to indicate which sample has the most pronounced properties or is more preferable than others, even in cases where the taster does not feel a difference, there is no difference. This is the technique of the so-called forced choice.

When applying the technique according to paragraph "b", the tasters are allowed to answer: "no differences", "no preferences".

The tasting report according to this method should contain the following information:

Purpose of testing;

Characterization of reference substances or products;

The number of tests, the number and composition of the tasting commission;

Testing conditions, especially if the "forced choice" methodology was used or the testing was one- or two-sided;

Results;

The paired comparison method is easy to prepare and implement, and does not require a large number of samples. The disadvantage of the paired method is the probability of an element guessing the correct answer. The reliability of the results obtained by the method of paired comparisons is checked using special tables.

Depending on the accepted probability (95 or 99%) for a different number of paired comparisons, the number of correct answers should not be lower than that indicated in the table.

triangulbright (triangular) method.

This method allows you to identify differences in the perception of two products using the triangle method.

Number of pairwise comparisons	Probability, %	Number of pairwise comparisons	Probability, %

Differences may relate to the whole complex of characteristics or to any individual property of the sample. The method is also used for selection and training of tasters, control of their working qualities. The developers of ISO 4120 recommend using this method in the following cases:

The number of tasters is limited;

There is no fatigue of the senses of the tasters.

According to the procedure described in the International Standard, tasters should be presented with three samples at the same time, two of which are identical. Samples are coded and assembled in blocks, for example, according to the following scheme: ABB, ABA, BAB, BBA, etc.

Tasters need to determine which of the three samples is different.

The tasting (testing) report must contain the following information:

Purpose of testing;

All information necessary for the complete identification of samples;

Accepted testing parameters;

Reference substances used;

Number of tests, number and composition of the commission;

Results;

Date, time, testing conditions;

FULL NAME. tasting leader.

The triangular comparison method is somewhat more complicated, but its accuracy is higher compared to the previous pairwise comparison method. The probability of guessing the correct answer in this case is 33%, while in the method of paired comparisons it is 50%.

In the practice of organoleptic analysis using the triangle method, tasters often make the mistake of pointing to one of two identical samples as a sample that has differences, which is called the "paradox of the indistinguishable". Such erroneous assessments can be avoided through careful preparation of tasters and good organization of the tasting itself.

"Duo-trio" method of sensory analysis.

The method is used to identify significant differences between two samples. These differences can be associated both with one organoleptic characteristic, and with a complex of such characteristics.

Number of correct answers required when using the triangular method

Number of pairwise comparisons	Probability, %	Number of pairwise comparisons	Probability, %

This method is not applicable either to determine preferences, or to assess the nature or intensity of perceived differences. There are two forms of the described method:

With changing control sample;

With a permanent control sample.

The permanent control technique is used as a quality control tool by a well-trained tasting panel when the control samples are well known to the tasters.

A sufficient number of samples are prepared, depending on the number of members of the tasting commission. All products must be prepared in the same way (same temperature, same dishes, same amount of food, etc.).

The glassware in which the samples are served must be obligatorily coded; usually this is a number of three arbitrary digits. Then series of four blocks of samples are formed in the following combinations: AkAB, AkBA, BkAB,

B BA In the first two blocks of the series, sample A is the control sample, and in the next two blocks - B. The prepared blocks of samples are distributed among the testers in a random order, simultaneously or sequentially. The testers are asked to select a sample that differs from the control.

If a constant control sample method is used, the possible combinations of samples will look like this: AkAB, AkBA, where Ak is the control sample in all blocks. Otherwise, this procedure is identical to the procedure with a changing control sample.

Purpose of testing;

Information necessary for the complete identification of samples;

Accepted testing parameters;

The form of testing - with a constant or changing control sample;

Results;

The two out of five method

The method is used for tasting products with slight differences. It can also be used as a training in the preparation and training of tasters.

As a rule, two identical samples A and three identical samples B are taken. Samples are assembled in blocks of five, coded and offered to tasters, for example, according to the scheme ABBAB, BBAAB, ABABB, AABAB, ABABA, BABAA. The task is to differentiate the samples in each block, highlighting A and B. This method is considered to be more efficient and workable than all the distinguishing qualitative methods described above. Its disadvantages include high labor intensity, rapid fatigue of the sense organs of tasters.

The test report must contain the following information:

Purpose of testing;

Information necessary for the complete identification of samples;

Accepted testing parameters;

The number and composition of the tasting commission;

Results;

Date of tasting (testing);

FULL NAME. tasting leader.

The "A" method is not the "A" of sensory analysis

The "A" -- not "A" method described is used in sensory analysis to:

Difference tests, especially for evaluating samples that have a different appearance (which makes it difficult to obtain strictly identical repeated samples) or leave different aftertastes (which makes direct comparison difficult);

Recognition tests, in particular to determine whether the tester or panel of testers can identify a new pulse compared to a known one

Impulse (for example, recognition of the sweet taste of a new sweetener);

Perception tests - to determine the sensitivity of the expert to a particular stimulus.

The taster first gets acquainted with the standard sample - "A", after which, in a series of coded samples, he searches for and identifies the product "A", as well as those different from the standard product - "not A".

The test report must contain the following information:

Purpose of testing;

Information necessary for the complete identification of samples;

Accepted testing parameters;

The number and composition of the tasting commission;

Results;

Date of tasting (testing);

FULL NAME. tasting leader.

Distinguishing Methodssensory evaluation: a group of methodsquantitative analysis

Quantitative discrimination methods allow you to quantify the intensity of a certain product property. This group includes dilution index and scoring methods.

Sensory Analysis Dilution Index Method

The method lies in the fact that liquid products are subjected to repeated dilution. As a rule, this dilution is carried out until the odor, taste, bouquet or flavor being studied is no longer felt at all, i.e. the intensity will become less than the threshold of sensation and the threshold of recognition. The higher the value of the dilution index, the more pronounced the intensity of aroma, taste, color and goodness of the product under study. Interesting research in pairs.

This method can be used to study the properties obtained by changing the technology (production, storage): one product is taken with a modified technology A, and the second (standard) is prepared according to traditional technology. Dilution allows you to determine the impact of changing technology on quality indicators. The method is quite widely used in the training of tasters, as well as in wine tasting.

It is recommended to apply this method to the study of solid products. To do this, 30 g of the substance are placed in a conical flask, 270 ml of distilled water heated to 60°C are added, after which the flask is closed tightly with a lid and shaken for 15 minutes. The resulting mixture is filtered; the filtrate is diluted with water with a solvent according to the above scheme until the complete disappearance of the investigated properties of the product.

Indicator (index) of taste, smell, color, tasty, etc. expressed as the number of dilutions or the percentage of the original substance in solution.

scoring method

With in English scoring is translated as scoring and is expressed either in points, or in verbal assessments, or the quality of the product being tasted is graphically depicted.

The scoring method allows you to quantify the qualitative characteristics of products, opens great opportunities in the study of the correlation between the organoleptic properties of products.

The method is as follows. The taster is offered two samples: one with the most pronounced properties being studied, the other with minimally pronounced properties. After that, a sample of interest to the commission is put up for tasting. The taster should, on a graphical or verbal scale, mark his impression of the product under study, whose characteristics are unknown. The graphic scale is a graduated segment of a straight line of a certain length, at the ends of which the limit values of the product properties (max, min) are marked. When comparing the properties of these two products with the properties of the test sample, the taster marks his impression on the scale with a dash or a cross. At the same time, it takes into account the distance from both ends of the segment.

40. Sensory analysisrennetcheeses

a) GOST requirements for the organoleptic properties of rennet cheeses

Cheeses are highly valuable food products produced from milk by enzymatic coagulation of proteins, isolation of the cheese mass, followed by its processing and maturation.

By technological features distinguish between rennet and sour-milk cheeses. Rennet cheeses are obtained by coagulation of milk proteins with enzymes of animal or microbial origin. In the production of sour-milk cheeses, for the fermentation of milk, ferments from sour-milk bacteria are used without rennet or with a small amount his.

Rennet cheeses are: hard (Swiss, Soviet, Altai, Dutch squared), soft (Roquefort, Adyghe) and pickled (brynza, suluguni).

Hard cheeses are characterized by a dense texture, and, depending on the production technology, they are divided into: pressed, with a high temperature of the second heating (Swiss, Soviet); pressed with a low temperature of the second heating (Dutch, Yaroslavl, Kostroma); self-pressing, with a low temperature of the second heating, ripening with the participation of the microflora of cheese slime (Latvian).

Soft cheeses are characterized by high moisture content, large grains, high content of lactic acid. AT pickled cheeses contains an increased amount of salt.

Sour-milk cheeses are divided into: aged (green) and fresh (tea, coffee). They are characterized by high humidity, soft texture and sour taste.

The organoleptic characteristics of hard rennet cheeses (the most common products of this group) must meet the requirements presented in the table.

Each cheese must be marked with the date of its production (day, month), the cheese brewing number and the production mark, consisting of the following designations:

Mass fraction of fat in dry matter (in percent);

Manufacturer's numbers;

The abbreviated name of the region (krai, republic) in which
the enterprise is located.

The shape and size of the production mark is established depending on the name of the cheese and the mass fraction of fat in the dry matter of the cheese.

Requirements for organolepticrennet cheese makers

(according to GOST7616-85)

On---and-m--e---but---in-anie cheese-ra	Or-ga-no-lep-ti-che-sky in-ka-for-te-whether
	Appearance	Taste and smell	Consistency	Picture	Color-tes-ta
Soviet	The bark is strong, even, without any damage and without a thick one-hundred-th under-cork-to-th layer, in--cr-yta pa-ra- fi-no-you-mi, in-l-name-rn-s, com-bi-ni-ro--va-nn-s with-hundred-va-mi or in-li-mer-us-mi captive-ka-mi under wa-kuu-mom.	You-ra-same-cheesy, sweet-to-va-ty, slightly spicy.		At the same time, the cheese has ri-su-nok with --- standing out of the eyes of a round or oval shape, equally-measure-but dis--- -p--ol--auger-ny throughout the cheese mass-se	From white-lo-go to weak-bo-yellow-that-go, one-n-o-r-one--ny all over the cheese mass
Swiss	The crust is strong, even, without damage and wrinkles, slightly she-ro-ho-va-taya with from-pe-cha-tk-ami ser- kicks. On the top of the awn-to-start-ka-et-sya durable su-hoi for years se-ro--in-ato-white-lo-go color. To-start--to-ae-tsya to cover the cheese pa--r-af-in-ov-ym, po-li-mer-us-mi or kom-bi-ni-ro-van- us-mi so-hundred-va-mi.	You-ra-same-cheesy, sweet-to-va-something-spicy.	Tes-something plastic-noe one-but-ro-one	At the same time, the cheese has a ri-su-nok co-standing from the eyes of a round or oval shape, equally-measure-but ras-p-ol- Auger-ny throughout the cheese mass-se.
Dutch round-ly (bru-sko-vy)		You-ra-zhe-nny cheese-ny, with on-li-chi-em ost-ro-you and light ki-slo-va-t-ost.	Tes - something - plastic - - - one - n - o - - - ro - bottom, slightly scrap - something on the gi-be	At the same time, the cheese has a ri-su-nok, consisting of round or oval eyes or an angled shape, equal to but ras----p--ol--ozhen-ny throughout the cheese mass-se	From white-lo-go to weak--b-o---same--lt-th, one--n-o-r-one--ny over the whole cheese mass
Yaroslavl	The crust is thin, even, without any time and without a thick one-hundred-th under-cork-to-th-layer, in a kr-yta pa-ra- fi-no-you-mi, kom-bi-ni-ro-van-ny-mi with-a-hundred-in-ami or in-or-mer-we-mi captivity-ka-mi under va-kuu-mom .	You-ra-same, cheesy, slightly sour-va-ty.		At the same time, the cheese has ri-su-nok, consisting of round or oval-shaped eyes, equal to - n-o-m-er - but races -po-lo-feminine throughout the cheese mass-se	From white-lo-go to weak--b-o---same--lt-th, one--n-o-r-one--ny over the whole cheese mass
Ko-st-rom-sky	The crust is thin, even, without any time and without a thick one-hundred-th under-cork-to-th-layer, in a kr-yta pa-ra- fi-no-you-mi, kom-bi-ni-ro-van-ny-mi with-a-hundred-in-ami or in-or-mer-we-mi captivity-ka-mi under va-kuu-mom .	Moderate-but you-ra-wife-ny, cheesy, sour-va-ty.	These are soft, plastic, one-n-or-one.	At the time, the cheese has a ri-su-nok co-standing from round or oval-shaped eyes, evenly spaced throughout the cheese mass	From white to slightly yellow, uniform throughout the cheese mass

b) cheese sampling for sensory analysis (according to GOST 26809-86)

When the number of packaging units in a batch is from 1 to 100, from 1 to 7 packaging units are selected. When the number of packaging units is over 100, they take 5%, but not less than 7 units. One circle is taken from each controlled packaging unit of hard cheeses, a bar from which, in turn, point samples are taken.

To assess the organoleptic indicators, a point sample is taken from one side of the cheese head, for this the cheese probe is inserted to a depth of % of its length. When sampling cheeses having the shape of a cylinder or a bar, the probe is inserted from the end side, closer to the center; in cheeses having a round shape, the probe is inserted at the top almost to the center of the head. A cortical layer, 1.5 cm long, is separated from the removed column of cheese. For research, take the remaining segment, about 4.5 cm long. the upper part of the cheese column is again inserted into the hole made by the probe, the surface of the cheese is poured with paraffin. For organoleptic analysis, a 50 g sample of cheese is isolated from each bar, circle or head of cheese included in the sample.

c) the procedure for sensory analysis of cheeses (according to GOST 7616-85)

The organoleptic quality indicators of cheeses, as well as their packaging and labeling, are evaluated on a 100-point system, where each indicator is given a certain maximum number of points in accordance with the data in the table:

Maximum scoring of organoleptic indicators of cheeses.

The scoring of the organoleptic indicators of cheeses is carried out in accordance with the table presented in GOST 7616-85, with all this, in the presence of defects and defects, a points discount is made for the corresponding indicator

Ball assessment of organoleptic indicators of cheeses

Na-ime-no-va-nie and ha-rak-te-ri-sti-ka in ---- to--az-at-el	Cheese press-sue-my, with you-so-so-pe-ra-tu-swarm of the second-ro-on-gre-va-niya	Cheeses are press-sue-my, with a low theme-pe-ra-tu-swarm of the second-ro-on-gre-va-nia	Sy-r-s sa--mo--pr-es-suyu--schi-esya, with a low theme----n--er--at-ura second-ro-on-gre- va-tion
	Discount points	Score	Discount points	Score	Discount points	Score
Taste and smell (45 points)
1. Personal
2. Ho-ro-shi
3. Good taste, but weak-bo you-ra-feminine
4. Satisfactory
5. Go-speech
6. Weak-bo-kor-mo-howl

8. Kor-mo-howl
9. Musty
10. Gorky cue
11. Sa-li-sty flavor
Con-si-sten-tion (25 points)
12. From-personal
13. Ho-ro-shay
14. Satisfying
15. Hard-day (rough-by)
16Re-zi-ni-flock
17. Non-connected (loose-barking)
18 Krosh-li-vai
19. Ko-lu-shaya (sa-mo-kol)
Color (5 points)
20. Normal
21 Not-equal-measured
Ri-su-nok (10 points)
22. Nor-small for dan-no-go vi-da cheese-ra
23. Not-equal-measured (by race-by-lo-same)
24.Rav-ny
25.Sche-le-vid-ny
26. From-day-st-vie eyes-kov
27. Small eyes
28, Set-cha-ty
29. Lip-cha-ty
Appearance (10 points)
30. Good-ro-shi
31. Satisfying
32. In-time-g-den-noe pa-ra-fi-ni-ro-van-noe or com--b-and--ni-ro--van--noe-cover
3 3. P ov-re-g-den-naya crust
34. Slightly de-for-r---m--ir--ova-ny cheeses
35. Up-to-exceeding crust
Upa-kov-ka and mar-ki-rov-ka (5 points)
36. Ho-ro-shay
37. Satisfactory

If there are two or more defects for each of the indicators of the scoring table (taste and smell; texture; pattern; appearance), the points are discounted for the most depreciating defect.

Depending on the overall score and assessment for taste and smell, cheeses belong to one of the varieties

Cheeses rated less than 34 points for taste and smell or overall score less than 75 points, as well as those that do not meet the requirements of the standard in terms of shape, weight and physico-chemical parameters, are not allowed for sale, but are subject to industrial processing for food purposes.

1. Duborasova, T.Yu. Sensory analysis of food products. Wine tasting Proc. allowance. - M .: Publishing and book trading center "Marketing", 2001. - 180s.

2. Motherland, T.G. Tasting analysis of products: Tutorial for stud. universities /T.G.Rodina, G.A.Vuks.-M.: Kolos, 1994.- 192 p.

3. Shchidlovskaya, A.F. Organoleptic properties of milk and dairy products: a Handbook. - M.: Kolos, 2000. - 280s.

short course

lectures

by discipline

"sensory analysis of food products"

Topic 1: " Basic terms and nomenclature of organoleptic indicators of food quality”

1. Basic terms

Sensory analysis Analysis using the senses, providing information about the environment through vision, hearing, smell, taste, touch, vestibular reception and interoception.

Organoleptic analysis Sensory analysis of foods, flavors and flavors using smell, taste, sight, touch and hearing. Note. The term is not synonymous with "sensory analysis", its meaning is limited by the object of study and the number of sensory organs.

Organoleptic The science that studies the properties of prepared foods, their intermediate forms and ingredients that cause a human sensory response.

Organoleptic evaluation Evaluation of the response of the human senses to the properties of the food product as an object under study, determined using qualitative and quantitative methods.

Stimulus A substance or electrophysical effect that causes sensation when interacting with chemoreceptors.

Notes. Stimuli that are recognized as typical for a certain sensation are called, respectively, gustatory, olfactory, etc. incentives.

flavor The complex sensation in the mouth caused by the taste, smell and texture of the food. Note. The smell and taste, which are not characteristic of this product, are called extraneous flavor.

2. Nomenclature of organoleptic quality indicators

Organoleptic analysis of food and taste products is carried out through tastings, i.e. research carried out with the help of the senses - a specialist - a taster without the use of measuring instruments.

2.1 Through sight determine: appearance, shape, color, luster, transparency.

Appearance - it is the overall visual sensation produced by the product.

The form - geometric proportions of the product.

Colour - the impression caused by a light pulse, determined by the dominant light wavelength and intensity.

Shine - the ability of the product to reflect most of the rays falling on the surface of the product, depending on its smoothness.

Transparency - property of liquid products, depending on the degree of light transmission through a liquid layer of a certain thickness.

2.2. Product quality indicators assessed by deep touch (pressure): consistency, density, elasticity, elasticity, stickiness, plasticity, brittleness.

Consistency - texture characteristic, reflecting the totality of the rheological properties of food products.

Density - the property of the resistance of the product that occurs when you click on it.

Elasticity - the ability of the product to return to its original shape after the cessation of pressure, not exceeding a critical value.

Elasticity - texture characteristic, determined by the rate and degree of restoration of the original dimensions of the product after the cessation of the deforming effect.

stickycost b is the ability of the texture, due to the force required to overcome the force of attraction between the surface of the product and the tongue, palate, teeth or hands.

Plastic - the property of the texture of the product not to collapse in the process and after the termination of the deforming effect.

fragility - the property of the texture of the product to collapse with small sharp deformations.

Texture - a term that refers to the macrostructure of food products and is characterized by a complex of sensations.

2.3 Product quality indicators determined by smell: smell, aroma, "bouquet".

Smell - a sensation that occurs when the olfactory receptors are excited, determined qualitatively and quantitatively.

Aroma - this is a pleasant harmonious smell characteristic of a given food product (wine, tea, spices).

"Bouquet" - this is a pleasant developing smell, formed under the influence of complex processes that occur during maturation, fermentation, fermentation (wine, cheese).

2.4 Using the sense organs in the mouth determine the following indicators: juiciness, uniformity, consistency, fibrous, crumbling, tenderness, astringency, taste.

Taste - a sensation that occurs when the receptors of the oral cavity are excited and is determined both qualitatively (sweet, sour, salty, bitter) and quantitatively (taste intensity).

juiciness - the impression of touch produced by the juices of the product during its chewing (juicy, low-juicy, dryish, dry).

Uniformity - the impression of touch produced by the particle size of the product (homogeneity of the chocolate mass).

Consistency - the touch that is felt when the product is distributed on the tongue (liquid, thick, dense).

Fibrousness - the feeling caused by the fibers that resist chewing the product.

crumbliness - the property of a solid product to crumble when biting, chewing. Due to the weak degree of adhesion between the particles of the product.

Tenderness - conditional term. This indicator is estimated by the resistance that the product has when chewing.

Astringency - a sensation caused by the fact that the inner surface of the mouth is constricted and dryness appears in the mouth.

Complex indicator " deliciousness ”is a complex sense of taste, smell, touch and auditory sensations.

Topic 2: "Psychophysiological foundations of sensory analysis"

2.1 Nature and factors of visual sensations

The general impression of a food product is created by external examination, i.e. visual (visual sensation).

In organoleptic analysis, the best lighting is natural (solar) diffused.

For less fatigue, the product in question should be at a distance of 25 cm from the eyes.

In the case of artificial lighting, the distance from the lamp to the test sample should be from 50 to 60 cm.

The organs of vision - the eyes are analyzers that are excited by waves of light rays in the visible region of the spectrum (from 380 to 760 nm). Electromagnetic waves (less than 380 nm) are ultraviolet radiation and are invisible to the human eye.

In addition, waves shorter than 760 nm are infrared radiation and are also invisible to the human eye.

Radiation with a wavelength of 380-470 has purple and blue colors.

480-500 nm - blue-green color;

510-550 nm - green;

560-590 nm - yellow-orange color;

600-760 nm - red color.

The visual sensation of color is determined by the properties of the object, as well as the properties of the visual analyzer.

With selective absorption and reflection of individual sections of the light spectrum, individual colors and shades are perceived by the eye.

If the light is reflected more than 90%, then the food product is perceived as white or colorless (salt, sugar).

When the product absorbs all or almost all the rays in the visible part of the spectrum, a black sensation occurs.

If a substance absorbs part of the rays, then its color is perceived by the eye from the reflected part of the rays. For example, red wine absorbs all rays of the visible part of the spectrum, except for the red ones, which it reflects.

All colors are divided into chromatic (colored) and achromatic (uncolored). All colors except gray are chromatic colors. Gray is absent from the spectrum and cannot be characterized by the wavelength of the spectrum. This color is determined only by the indicator of brightness (lightness).

To characterize the perceived color, the following concepts are used:

Color tone - determined by the wavelength of the visible part of the spectrum.

Saturation, or purity of color, described by the terms weak, strong, pale, dull, saturated, etc.

Color brightness characterized by the terms dark, light, bright, while meaning its density, which does not change the shade. The impression of brightness also depends on the background against which the object is viewed.

Lighting brightness affects the perception of color. For example, when the light is reduced, yellow can be perceived as brown.

Artificial light sources are poor in short-wavelength rays. For example, in sunlight, an object appears blue, but in incandescent light it appears almost black.

The perception of color is influenced by a number of subjective factors: the physiological characteristics of the taster, age, qualifications, color vision disorders, tasting goals. If there are genetic abnormalities in the retina, for example, there are no photoreceptors in certain parts of the spectrum, then they do not distinguish the corresponding colors.

Approximately 10% of people have color vision anomalies; among them are more common people who do not distinguish between green, less often - red, even less often - blue. Extremely rare cases of complete color blindness, when objects are perceived as achromatic. Men predominate among colorblind people.

The maximum sensitivity for the human eye is found in the violet, green and yellow regions of the spectrum.

According to the theory of trichromatic color vision (G. Jung and G. Helmholtz), all colors and shades perceived by the eye are obtained by mixing in different ratios of the three main color components, to which three types of cone photoreceptors are sensitive. Blue cone cells are excited when illuminated with monochromatic color at a wavelength of 445-450 nm, corresponding to blue-violet; green cones are sensitive at a wavelength of 525-535 nm, which corresponds to green; yellow photoreceptors are excited by rays with a wavelength of 555-570 nm, characteristic of orange.

Cone-shaped photoreceptors have a high resolution, they are sensitive to color, much less sensitive to light. They require good lighting, preferably natural, to function properly. Rod cells have low resolution, are insensitive to color, but are very sensitive to light. In low light, only rod-type vision functions, and color vision is practically absent.

To accurately describe the visual sensations, the taster needs to know the nomenclature of colors.

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Topic №1 Sensory (organoleptic) analysis

General characteristics of organoleptic analysis and its purpose

Organoleptics is a science that studies the properties of food products. industrial molds and ingredients that cause a human sensory response.

Organolectics is the science of the sensory properties of media and ingredients and their measurements with the help of human senses, biological objects and artificial systems.

There are qualitative and quantitative organoleptic analysis. Qualitative Analysis object is used to characterize the manifestation of its properties without their quantitative assessment. Quantitative analysis is designed to quantify the strength of the properties and is based on the quantitative characteristics of a person, it is carried out only by experts. The main purpose of quantitative analysis is to check the compliance of products with the requirements of TNLA, determine the level of product quality, determine the safety and damage of products.

Classification of types of organoleptic analysis and their characteristics

The main types of analysis are determined by the totality of the senses (sight, hearing, taste, smell, touch, intuition). There are the following types of organoleptic analysis: visual, olfactory, gustatory, tactile.

The visual method is used at the first stage of analysis as a non-destructive control method, it is the most sensitive method, used to characterize shapes, sizes, etc.

The quantitative characteristics of taste analysis are the threshold of sensation, the threshold of recognition, the threshold of discrimination, the threshold of saturation. The intensity of taste is expressed in points, taste stability. Adaptation is the time during which taste sensitivity begins to decline.

Tactile organoleptic analysis

Touch - the perception of texture, shape, size, mass, consistency, pressure, temperature. There are 3 types of touch receptors:

1) Responds to touch - unstable deformation.

2) Responds to pressure - static deformation.

3) React to vibration - pulsating deformation.

Texture– the macrostructure of the object (hard, fibrous, sticky, brittle, crumbly, homogeneous, heterogeneous, rough, etc.).

Elasticity is a texture characteristic determined by the rate and degree of restoration of the original dimensions after deformation.

Plastic- the ability to maintain deformation without destruction after the cessation of exposure.

fragility- the ability to collapse under deformation.

Consistency- a set of texture properties that characterize its rheological properties, liquid, solid, gaseous. The texture includes mechanical characteristics (associated with force action), geometric characteristics that characterize the macrostructure.

Organization of sensory studies

To get the best effect from the use organoleptic methods assessment of the quality of goods, it is necessary to have qualified tasters, the assessment of the professional suitability of tasters is carried out based on the specifics of the task. Sensory sensitivity is divided into 4 groups: sensitive, medium, satisfactory, low. To work as tasters, persons with satisfactory sensitivity and above are selected.

Professional selection of tasters is a system of measures aimed at identifying individual-personal and interpersonal qualities of a person for his successful activity.

The assessment is carried out in 3 stages:

1) Clinical trials.

2) Assessment of sensory sensitivity.

3) Psychological tests.

When testing for taste color blindness, the test subject is offered samples of basic tastes (a model solution with a sufficiently high content of substances that he must recognize).

To test the olfactory ability, the following solutions are used:

Sensory sensitivity of the sense organs and smell is tested for recognition and discrimination. The following solutions are used to determine recognition sensitivity:

To determine the olfactory sensitivity are used:

To determine the distinctive and recognizing taste sensitivity, different concentrations of data or other substances are used, and gradation is also carried out on a 4-point scale.

The formation of groups of tasters includes 4 stages: selection, theoretical training, training, testing. To evaluate the work of tasters, the repeatability index is used, which is a statistical value of the correctness of the assessment in the analysis and use of point scales and expresses the average deviation of the assessment results during repeated tests of the same products.

The professional awareness of the taster should include the relevant knowledge of the merchandiser, production technology, storage of products, as well as knowledge of the factors influencing sensory research, methods for developing sensory abilities, their application and knowledge of the possibilities of suppressing subjective factors. Training of selected persons consists of theoretical training, practical part. Selected trained and trained tasters should be regularly tested to ensure the reliability of the results.

From the selected candidates, tasting commissions are formed, which are production and research. Production identify and reject a low-quality product, as well as establish the causes of its occurrence and take measures to eliminate the causes (tasters must have medium sensitivity, level 2). Study groups determine the relationship between individual quality indicators, improve analysis methods, and solve other scientific problems (sensitivity level at least 3). As a rule, the commission consists of 5-9 people headed by the chairman. During the work of the commission, tasters should be guided by the instructions developed for a particular case, containing an evaluation table, a verbal description of each level of product quality, and an analysis methodology. Each taster evaluates the products individually in a specially equipped laboratory, the results of the work are recorded in the tasting sheets, and the results of the group's work are summarized in the protocol for processing the tasting sheets. The results of the work of the tasting commission are expressed in points as the arithmetic mean value awarded to each sample. Reproducibility of test results is characterized by repeatability and comparability.

Repeatability- a quantitative expression of the magnitude of random errors of the tasting commission, when it is in the same composition, under the same test conditions, one and the same day receives different results of the assessment of the same sample of the product.

Comparability is a quantitative expression of the amount of random error that occurs when different panels obtain different results for the same sample under similar test conditions.

Sensory analysis methods

1) Preferences- is based on a logical conclusion and is used for consumer evaluation of goods, in this case, the respondent answers the question of whether he likes or not the proposed product. This method uses a scale: like it very much, like it, dislike it very much, dislike it very much. Questionnaires are used to obtain more accurate answers. These methods are used by specialists, as well as non-professionals.

2) Comparison Methods, allow you to determine the difference between several samples, as well as the magnitude and direction of these differences. Methods can be symmetrical or asymmetric (different numbers of sample units).

3) Pairwise Comparison Method, consists in the fact that the subjects are given two samples. It is necessary to establish the difference between them or which test is more intense, preferable. The method is simple and does not require a large number of samples.

4) Method of triangular comparisons, the taster is provided with three samples, which include two identical samples and one different.

5) Two-pair method, the taster is provided with two unknown samples and a standard, it is necessary to select a sample corresponding to the standard.

6) tetrad method, uses four samples, which in pairs slightly differ from each other in terms of orgonoleptic properties, you need to choose the best sample.

7) Arrangement method, assumes the presence of three or more samples and the taster must arrange the randomly submitted samples in order of increasing intensity or decreasing of any property (when studying the effect of changing the recipe on some indicators of product quality).

8) Dilution method, the liquid product is subjected to a series of dilutions until such a concentration is obtained at which the studied features are not detected orgonoleptically, and the intensity of the features is estimated by the number of dilutions. When studying the indicators of dense products by this method, extraction can be used.

9) Scoring Methods, the results of product evaluation are expressed by means of dimensionless numbers called points, the totality of which in a certain range forms a point scale. There are four types of scales: nominal, ordinal, interval, rational.

10) profile method, each of the organoleptic properties are evaluated by the tasters for the quality of the intensity and the order of detection. The flavor profile of the beer is rated as follows: aroma: hoppy, fruity, yeasty, sour, malty, resinous, finil acetic acid; goodies: salty, sweet, sour, fruity, bitter, yeasty, malty, acetic acid phenyl, astringently tart;

Bouguer-Lambert-Beer law

The Bouguer-Lambert-Beer law: the optical density of a solution is directly proportional to the concentration of the light-absorbing substance, the thickness of the solution layer and the molar coefficient of light absorption.

E - a constant value for a particular substance does not depend on the concentration, length and intensity of the incoming light flux, but depends on the wavelength. The graphical dependence of the optical density A of the solution on the wavelength of light is called the absorption spectrum.

The optical density of the solution is measured by photoelectrocolorimeters (FEC). And spectrophotometers.

The principle of operation of the FEC is that the light flux passing through the cuvette with the solution enters the photocell, which converts the light energy into electrical energy measured by a microammeter.

Scheme of a single-beam FEC:

FEC operation: the diaphragm is adjusted so that the microammeter needle deviates to the full scale up to division 100 (cuvette with pure solvent). Without changing the openings of the diaphragm, a cuvette with the analyzed colored solution is placed, while the arrow of the microammeter shows the light transmission (T, %), which is reshielded to the optical density.

A=-lg T T=I t /I o

To measure light absorption, choose a wavelength at which the minimum detection limit is possible.

FECs are equipped with a special cassette with light filters; the light filter used must transmit rays of such length that is absorbed by the analyzed solution.

The optical density A of the analyte can be measured sequentially with all filters and choose the one with the highest optical density.

Analytical tasks , solved by photometric methods:

1) Definitions based on the intrinsic light absorption of substances (determination of caffeine in tea).

2) Determination associated with the formation of intensely colored products when a colorless reagent is added to a colorless solution of the analyte (determination of proteins, nitrites).

3) Definitions based on the measurement of the color intensity of the excess of the colored reagent (determination of sugars by excess of potassium dichromate).

Spectrophotometer scheme:

Spectrophotometry is based on the same laws of light absorption as photoelectric colorometry. The ability to measure the optical density of both visible and near UV and IR light. Accurate results are obtained when the optical density is approximately equal to 0.4, and if the OD is 0.8 and more, then use the cuvettes with a shorter length, if the OD is 0.1, then use the cuvettes with a longer length.

Fundamentals of spectroscopy

The spectroscopic method is a method based on the interaction of matter with electromagnetic radiation.

Electromagnetic radiation is a type of energy that propagates in a vacuum at a speed of 300,000 km/s and which can appear in the form of light, thermal, UV radiation, micro-, radio waves, gamma and X-rays.

The properties of electromagnetic radiation are described on the basis of the theories of its wave and corpuscular nature.

To describe the phenomena of absorption and exclusion of electromagnetic radiation, it is necessary to use ideas about its corpuscular nature. In this case, the radiation is presented in the form of a stream of individual particles - fatons. The energy of such a particle is in strict accordance with the radiation frequency.

Atomizers

The simplest way to transfer a sample to an atomic state is a flame. Subsequently, to improve the sensitivity of the determination, an electrometric method of atomization was proposed - graphite furnaces.

In the flame atomization method, the sample solution is sprayed into the flame in the form of fine droplets, the combustible mixture to support the flame consists of a combustible gas and an oxidizer gas.

The oxidizing agent can simultaneously serve as a spray gas or be supplied to the burner separately (auxiliary gas), an acytylene-air mixture is used to determine most elements, in the flame evaporation constituent parts samples, their dissociation into free atoms excitation atoms under the influence of external radiation, ionization atoms. The same processes take place in atomizers of other types.

Electrothermal method atomization - using graphic tubes heated by electric current (graphite cuvettes). The length of the tube is 30-50mm, the inner diameter is about 10mm.

A sample flow rate of approximately 10 µl is introduced into the cuvette and heated according to a special temperature program by applying voltage through metal contacts (up to 3,000 degrees Kelvin), by means of a programmed temperature increase to 100-110 ° C, the sample solution is first dried in a protective atmosphere of an inert gas (orgone), then the sample is incinerated raising the temperature to 500-700 degrees during the ashing process, volatile components are removed, then the temperature is raised to 2-3 thousand kelvin, while the processes of dissociation, excitation, and others described above occur.

Monochromator

The role of the monochromator in AAS. It consists in cutting off excess lines of emission from a hollow cathode lamp, molecular bands and extraneous external radiation. Due to too wide spectral bandwidths, the use of filters in AAS is not possible. Usually, diffraction gratings containing up to 3 thousand lines per millimeter are used for monochromatization in AAS; photoelectronic multipliers are used as radiation receivers.

A phaton hits the cathode and knocks out an electron from it in the vacuum space between the cathode and the anode, an electric current arises. An electron that has flown out of the cathode bombards the dynode closest to it and knocks out several secondary electrons from it, which in turn bombard the next dynode. As a result, the number of ejected electrons increases like an avalanche.

Quantitative analysis according to the Bouguer-Lambert-Beer law.

Practical use: up to 70 metals can be determined by the AAS method, non-metals, as a rule, cannot be directly determined, there are methods for indirect determination of non-metals, both trace and fairly high contents can be determined by the AAS method.

Disadvantages of AAS: single element method of analysis (requires a new hollow cathode lamp), a drum with lamps is installed for faster detection.

Quantitative Analysis

Quantitative analysis. A feature of the RPA method is the presence of strong matrix effects. In addition to the direct excitation of the atoms of the element being determined by primary X-rays, a number of other phenomena can be observed. Interactions of radiation with matter: excitation of the atoms of the determined element under the action of secondary radiation from the atoms of the matrix elements; absorption of primary radiation by matrix elements - the intensity of the exciting radiation decreases and the analytical signal decreases; absorption of secondary radiation by matrix atoms 9 underestimation of the analytical signal). Ways to correct matrix effects:

1) Use an external sample standard that matches the sample being analyzed as closely as possible. In this case, matrix effects equally affect the count rate for both the sample and the standard.

2) Special sample preparation - the sample can be heavily diluted with a weakly absorbing material sucrose or cellulose, the influence of matrix effects is greatly reduced.

3) Calculation method - the use of theoretical ideas about the interaction of matter with X-rays.

Practical use

Practical use. The XRF method determines the main components in the analysis of materials of the metallurgical, construction, glass, ceramic, fuel industries, geology, and more recently for the analysis of objects environment in medicine and research purposes. The RPA method can determine 83 elements from fluorine to uranium. Analyze solid samples - powdery, glassy, metal.

Powders should have a grain size of less than 30 micrometers to ensure reproducibility, they are pre-compressed into tablets without filler or mixed with cellulose or graphite. For homogenization of the sample, melting is used, fused with sodium or lithium to a glassy mass. Metal samples are analyzed as is.

The main advantage of the RPA method is the possibility of non-destructive testing; it is convenient for the analysis of the near-surface layer of materials and works of art. Prototyping spectrometers are being produced that are easy to deliver to the analyzed object.

Radiation sources

Incandescent solids are used as radiation sources in the IR region. For such sources, the distribution of the radiation intensity along the lengths. The waves depend on temperature and are described by Planck's law. This distribution is not uniform and has a clearly defined maximum. For IR, it is necessary to cut off intense short-term radiation in the visible region and leave longer-wavelength and less intense radiation in the IR region.

The most common sources of IR radiation are Nerst pins made of yttrium and zirconium oxides, as well as silicon corbide.

They are heated to high temperatures using electric current (800-1900 o C).

For the far infrared region, special radiation sources are used - mercury discharge lamps. high pressure. In the near, you can use incandescent lamps with a tungsten filament.

Sample preparation

Sample preparation is laborious compared to other spectral methods. For gaseous samples, special evacuation is used (thickness from mm to m). Most often, liquid samples are analyzed, while neither water nor alcohol is suitable as a solvent. Use organic solvents purified from water. As solvents are used: nujol, acetone, benzene. In order to have the own absorption of the solvent, thin cuvettes (up to 1 mm) are used as little as possible.

Solid samples are analyzed directly if a thin layer can be prepared from the material.

The powdered sample is mixed with nujol until a homogeneous mixture is placed between two cuvette windows. The windows are pressed against each other, getting rid of air bubbles.

Monochromators

In ICS, both prisms and diffraction gratings can be used as monochromators. Depending on the investigated spectral range, quartz, LiF, NaCl, KBr, CsI prisms are used. At present, grating monochromators predominate. Advantages:

High uniform resolution,

Mechanical and chemical resistance,

Wide operating range of the spectrum.

Detectors

Thermocouples are used as detectors. The thermocouple converts the infrared radiation energy into heat and then into electricity. The resulting potential difference is recorded in the usual way.

The balometer works on the principle of a resistance thermometer. The working material is metal or alloy (platinum, nickel, etc.), the electrical resistance varies greatly with temperature.

A common problem in measuring the intensity of IR radiation is the presence of significant environmental thermal noise with a small useful signal. Therefore, IR radiation detectors are isolated from the environment as much as possible.

IR spectrometer device

As a rule, an IR spectrometer operates according to a 2-beam scheme: 2 parallel light fluxes are passed through a cuvette with an analyzed sample and a reference cuvette - this makes it possible to reduce errors associated with scattering, reflection and absorption of light, cuvette material and solvent. The light emitted by the source is divided into 2 streams: one of which passes through the measuring cuvette, and the second through the comparison cuvette. Then both streams fall on a mirror rotating at a certain frequency, this mirror is divided into 4 equal sectors (90 each), 2 of them are transparent, and 2 others are reflective. Light fluxes alternately fall on monochromats (according to the Littrow scheme). A light beam is reflected by a Littrow mirror and passes through the prism twice. Then, with the help of a system of mirrors, it is directed to the detector. The spectrum is scanned by turning the Littrow mirror or prisms. A highly sensitive thermocouple is used as a detector. The electrical circuit of the amplifier is assembled so that at the same intensities of the measured light flux and the reference flux, the resulting current is zero. When light is absorbed in the measured cuvette, the intensity of the corresponding light flux decreases. This causes an electric current to appear in the circuit, which drives the motor. The motor moves the attenuator wedge into the comparison light by enough to equalize the intensity of both signals again, so the position of the wedge characterizes the degree of light absorption. At the same time, information about the position of the wedge is fed to the recording device. Data on the current wavelength is determined by the position of the Littrow mirror.

IR spectrometer with Fourier transform (on your own, will not be on the exam).

Qualitative Analysis

Qualitative analysis is used to solve problems various types. The IR spectrum allows you to establish the nature of the substance, compare the experimental spectrum of an unknown substance with the spectra available in the spectral library. The IR spectrum allows you to find out whether the structure of the substance corresponds to the proposed formula, and also to choose the most probable among several structures. We can assume the structure of matter. When studying the structure of substances by IR spectroscopy, it is necessary to adhere to the following basic provisions:

1) To register the IR spectrum, a pure substance should be used;

2) Need to know Additional information about the substance (what class of substances, etc.)

3) The absence of a band in a certain frequency range is a reliable proof that the corresponding structural fragment is absent in the molecule. However, the presence of a band does not yet indicate that the molecule contains this group.

4) For the group under consideration, one should find all its characteristic spectral bands

5) First of all, it is necessary to investigate the bands in those regions of the spectrum where there are few of them.

6) A reliable assignment of the structure is possible only when all the characteristic bands are identified and there is a spectrum of a similar constructed compound for comparison.

This method is most often used together or in combination with other methods.

Quantitative Analysis

For quantitative analysis, the mid-IR region is not as suitable as UV or visible. The intensity of radiation sources here is low. The sensitivity of the detectors is low. The complexity is created by the very small thickness of the cuvettes, which is difficult to reproduce or measure. The level of scattered radiation in the IR region is much higher than in the UV and visible. Careful calibration using standard samples, as well as the use of modern equipment, make it possible to overcome these difficulties to some extent and use IR spectroscopy for quantitative analysis. Via this method determine individual aromatic hydrocarbons, glucose in blood serum, air pollutants (CO, acetone, ethylene oxide, chloroform). The near-IR region is of great importance for IR analysis. Near-IR spectroscopy can directly determine the octane number of gasoline.

optical microscopy

The microscope is optical instrument to obtain enlarged images of objects.

The microscope consists of two systems of an eyepiece and an objective. The lens is located close to the sample (epsilon). Creates the first magnified image of the object (epsilon '). This image is enlarged by a factor of 2 or more to the eye of the beholder epsilon"". An epsilon """ image is formed on the retina at a much larger angle, which determines the high magnification of the microscope.

1677 the microscope was invented, Livenhoek first saw the simplest organisms, looked through a sample of water from a groove. Modern microscopes use complex optical systems, and also create special conditions illumination of objects. As a result, such a microscope can magnify several thousand times. N opt is approximately equal to 10*10*10.

If the object is illuminated with ordinary white light, then the image of the object is not sharp. In a lens system, optical beams of rays of different colors do not coincide, they have a different path, as a result, the image for each wavelength is shifted, since the optical system decomposes white light into a spectrum. As a result, small details become indistinguishable. In order to organize monochromatic illumination in microscopes, special lamps and optical filters are used, the closest to monochromatic light of one wavelength is the radiation of some lasers. Even in the case of monochromatic illumination, there is a limit to the resolution of the microscope, this limit is due to the wave nature of light, which manifests itself in the diffraction of the light wave at the edges of the lenses of the optical system.

Picture. BUT - general form diffraction pattern when observing two small objects at a small angular distance. B is the Rayleigh resolution limit of two points.

In optical microscopy, to characterize the possibility of increasing the actual microscopy, the concepts of the limiting angle of resolution and resolution are used. The limiting angle of resolution is the angle at which the first dark diffraction pattern passes through the bright center of the second, depends on ƛ of the illuminating object, while the minimum distance resolvable by the microscope is determined by the formula:

A is a numerical operation. A≤1, depends on lens material and material.

The resolving power of a microscope is the reciprocal of the limiting angle of resolution. Rayleigh's rule - the maximum resolution of an optical microscope cannot be more than half the wavelength of the light illuminating the object.

Electron microscopy.

It was invented in the 1930s, in order to increase the resolution, it was proposed to use photon radiation (electron flux) instead of light radiation, the wavelength of which is determined by the formula:

ƛ=h/mv – Debroglie wavelength.

h - 6.624 * 10 -24 J * m

m - 0.9 * 10 -27

v is the electron speed.

The limiting resolution of electron microscopes is 1000 times greater than that of optical microscopes. In order to obtain an image in a microscope, a stream of electrons emitted by a hot cathode is used. Electrons are controlled by external electromagnetic fields. An electronic image is formed by electrical and magnetic fields as well as light optical lenses. The device for focusing and scattering an electron beam is called an electron lens. Since the eye cannot directly perceive electron beams, they are directed to luminescent monitor screens. You can see individual atoms. The scanning microscope (SEM) is the most widely used. In such a microscope, a thin beam of electrons with a diameter of 10 nm scans the sample along horizontal lines and synchronously transmits a signal to the monitor, similar to the operation of a TV. The source of electrons is metal (tungsten), from which electrons are emitted when heated - thermionic emissions. The need to work in full vacuum, since the presence of gases inside the chamber can lead to its ionization and distort the results. Electrons have a destructive effect on some things. Allows you to see the atomic lattice, distinguish the atom, but its resolution is not enough to see the atomic structure or the presence of chemical bonds in the molecule. For this purpose, neutron microscopes are used.

neutron microscopes. Neutrons enter together with protons, are part of atomic nuclei and have a mass 2000 times greater than electrons. The resolution is 1000 times higher than that of electron microscopes. The main disadvantage of neutrons cannot be controlled by electromagnetic fields, so it is very difficult to build them.

Atomic force microscope

Atomic force microscope (1986), similar to the principle of operation of a tunneling microscope. Measures the bond strength of atoms. The approach of the needle leads to the fact that the atoms of the needle are increasingly attracted to the atoms of the sample, the attractive force will increase until the needle and the surface approach so close that their electron clouds begin to repel electrostatically, with further approach, the electrostatic repulsion will exponentially weaken the attractive force. These forces are balanced at a distance between atoms of 0.2 nm. As an AFM probe, a diamond needle with a radius of curvature of less than 10 nm is usually used, which is fixed vertically at the end of a horizontal plate - a console.

The tip of the scanning needle is called tip, and the console is called cantilever. When the force acting between the surface and the tip changes, the console deflects and this is recorded by a sensor (laser beam). The laser beam is reflected onto a photodiode and the readings are then transmitted to a computer. The advantage is the ability to study the structure of electrically conductive samples and non-conductive materials.

Varieties of ASM:

1) Magnetic force microscope, a magnetized tip is used as a probe. Its interaction with the sample surface makes it possible to register magnetic microfields and represent them in the form of a magnetization map.

2) With an electric force microscope, the tip and the sample are treated as a capacitor, and the change in capacitance along the surface of the sample is measured.

3) Scanning thermal microscope. Registers the temperature distribution over the surface of the sample, the resolution reaches 50 nm.

4) Scanning friction microscope. The probe scrapes across the surface, leaving a friction map.

5) Magnetic resonance microscope.

6) Atomic power acoustic microscope.

№4 Physical research methods.

Separate electrophysical and thermal methods.

Two-probe method

Used to determine the resistivity of regularly shaped samples with a known cross section, for example: used to control the distribution of ρ (resistivity) along the length of ingots of semiconductor material. The range of measured values is 10 -3 to 10 4 ohm*cm.

When using the two-probe method, ohmic contacts are made on the end faces of the sample, through which an electric current is passed along the sample, on one of the surfaces along the current line, two contacts are installed in the form of metal probe needles having a small area of contact with the surface, and the potential difference is measured between them. If the sample is homogeneous, then its resistivity is determined by the formula:

S is the distance between the probes.

A is the cross-sectional area.

I - current strength.

The current through the sample is supplied from an adjustable source direct current. The current strength is measured with a milliammeter, and the potential difference with an electronic digital voltmeter with a high input resistance. The condition for using the two-probe method for the quantitative determination of Po is the one-dimensionality of the spatial distribution of equipotential current lines (the presence of a resistance gradient along the sample and inaccurate observance of geometric dimensions leads to an increase in the measurement error).

Four-probe method.