Organoleptic characteristics are the most important in determining the commercial grade of tea. Based on their analysis, one can judge the origin of tea, the quality of raw materials, compliance with the production and storage technology.

The organoleptic characteristics of packaged black long tea were assessed in accordance with GOST 1938-90 "Packaged black long tea. Specifications".

results sensory evaluation object No. 1 black long leaf broken leaf tea "Princess Kandy" are presented in Table 2.3. Since the manufacturer did not indicate the type of this tea according to the domestic classification, the examination will be carried out for the compliance of the tea with the highest grade.

Table 2.3

Analysis of the organoleptic characteristics of the Princess Kandy tea showed that the object has a weak aroma with a slight astringency, the taste is pleasant, without extraneous influences, the infusion is "average", the color of the boiled leaf is uniform, and the appearance of the tea is even, lamellar, with wood petioles. Thus, the object under study does not comply with GOST 1938-90 in terms of top grade and only the first grade can be assigned to it.

The organoleptic characteristics of object No. 2 "Princess Gita" tea are presented in Table 2.4. granulated tea cannot be assigned the highest or grade "bouquet".

Table 2.4

The results of the examination of the quality of tea "Princess Gita"

Analysis of the organoleptic characteristics of object No. 2 "Princess Gita" tea showed that the taste and aroma of this sample are rough and tart, and the infusion is slightly unclear, the color of the boiled leaf is brown and uniform, and the appearance of the tea is a spherical shape. From this we can conclude that this object does not correspond to the first grade according to the standard, and only the second grade can be assigned to it. Conclusion: this object meets the requirements of the second grade according to GOST 1938-90.

Organoleptic characteristics of object No. 3 "Princess Nuri" tea are presented in table 2.5. This object can be assessed according to the standard for compliance with the highest grade.

Table 2.5

The results of the examination of the quality of tea "Princess Nuri"

Analysis of the organoleptic characteristics of object No. 3 "Princess Nuri" tea showed that the object corresponds to the highest grade in all indicators of the standard, and has a delicate aroma, pleasant taste with astringency, transparent, bright infusion, color of a boiled leaf Brown, and the appearance is uniform, even and twisted, without foreign inclusions.

In this work, three batches of the product were investigated for each name. As a result of the examination, the following conclusions were made: consignments do not differ in labeling, i.e. they are identical. When evaluating the qualitative organoleptic indicators of different consignments, differences were also not revealed.

Thus, the organoleptic assessment showed that object No. 1 corresponds to the second grade of GOST 1938-90, object No. 2 corresponds to the second grade according to the standard, and object No. 3 corresponds to the highest grade according to GOST 1938-90.

Introduction

An analysis of the development programs of educational institutions that received support within the framework of the national project shows that knowledge of information technologies, the ability to take care of one's health, engage in communication, and solve problems are new components of the modern quality of education that is in demand by society. The most characteristic is the transition from the mindset to memorization a large number information for the development of new types of activities - design, creative, research.

The project activity of students to master operational knowledge in the process of socialization seems to be promising for a modern school. In the twenty-first century, volumes teaching material, high requirements for the modern student and teacher push the teacher to search for innovative forms of activity, interactive methods, including the use of projects. This type of activity is more multifunctional than others.

The project method involves the use of a wide range of problem studies, the search for methods focused on a real practical result that is significant for the student and teacher, and on the other hand, a holistic development of the problem, taking into account various factors and conditions for its solution and implementation of the results.

The project activity may be preceded by a brainstorming session, during which new interesting problems for the students will emerge. During the project, students synthesize knowledge in the course of their search, integrate information from related disciplines, look for more effective ways to solve project problems, communicate with each other. Joint activity really demonstrates the broad possibilities of cooperation, during which students set goals, determine the optimal means of achieving them, and comprehensively test the competence of the individual.

Project activity clearly demonstrates the possibilities of mono- and poly-subject, individual and group projects.

The object of this work is the process of development of education as an integral pedagogical system, and the subject of this research is innovative pedagogical technologies as an integral part of the object of research.

The purpose of this work is to show that the project awakens the student to show intellectual abilities, moral and communicative qualities, to demonstrate the level of knowledge and general educational skills, goal-setting, the ability to self-education and self-organization, in project learning, priority is given to the independent work of students in a team, which contributes to their development. social consciousness.

An educational and cognitive project is a time-limited, purposeful change in a certain system of knowledge based on specific requirements for the quality of results, a clear organization, and students' independent search for a solution to the problem. For a certain time (from one lesson to several months), students solve a cognitive, research, design or other problem.

The forms of project implementation are different: it can be a printed work, an article, a report to a conference, a wall newspaper, an almanac, a multimedia presentation, a creative report.

But the main thing in all this is to gain new knowledge in the course of solving educational and cognitive problems.

Modern educational project

One of the directions of the reform of the general education school is the transition from traditional to developing humanitarian educational technologies.

Methods of activity-based organization of training are gaining special relevance. Only through active independent activity is the development of each student possible. Great opportunities for the transition from a knowledge-based learning model to an ability-based model are project-based learning that grew out of the project method.

A modern educational project is a didactic means of enhancing independent cognitive and creative activity, the formation personality traits trainee. The use of the project method, in particular, in mathematics lessons, allows students to form an objective system of ideas about their knowledge, opportunities and abilities to implement them.

Students master the ability not only to understand the goal of their learning, but also to set it independently, to define specific tasks, to program their own activities, to select adequate means of achieving the goal, to determine the sequence of actions, to determine the sequence of actions.

A necessary stage in the work on a project is an objective assessment of the final and intermediate results of their actions. Essential in this process is the ability to correct your actions, that is, to reconstruct these actions in such a way that the result meets the requirements. For this purpose, it is imperative to reflect on each stage of the project activity.

Thus, the basis of project-based learning is the reflexive-activity paradigm, which involves active actions of students, mandatory reflection, which leads to a conscious understanding of problems, contributes to self-development. With the reflexive-activity method of teaching, the teacher's position changes, as well as the requirements for his professional qualities. From a bearer of ready-made knowledge, he turns into an organizer of cognitive, research, independent activities of students, performing the role of a competent consultant.

Reflexive activity learning involves three main functions of a teacher.

The first and main one is the creation of conditions for the inclusion of students in independent cognitive creative activity.

The second is to stimulate a situation of success for each student.

The third is carrying out, together with the students, the reflection of the activity, the process of self-change.

The priority form of interaction in the classroom with the use of project activities is "teacher - group".

The project activity is based on collective work on solving life, by the students themselves, of the practical tasks set.

A significant part of the project activity - collecting materials, applying the results obtained in practice, the most important moments at which students learn about life and learn to apply their knowledge to it - takes place outside the walls of the school.

The laboratory for the design method is the entire surrounding life, and the teaching aid is all the surrounding objects and phenomena to be studied in connection with the intended task. Work skills, including learning skills, are acquired in the very process of work and the faster and stronger the more students are interested in achieving the intended goal.

Project-based learning is based on the independent activity of students, since true learning goes through activity. The teacher should not so much teach as give a thought, and not so much expound as direct, not so much impose, but respond to a call for leadership. The attention of the students is kept tense all the time, they are required to be constantly active, they must plan for themselves a program of studies and intensively carry out it in order to successfully work on one task and take on another. Thus, the use of project activities makes it possible to bring educational work closer to research work.

Stages of work on a project

The progress of work on a project can be defined in general terms through the following stages:

1. Preparation for work on the project:

Determination of the theme and goals of the project;

Formation of groups to work on a project;

Planning stages of work.

2. Working on a project in groups:

Work planning;

Study;

Registration of conclusions and results.

3. Presentation - project defense.

4. Project evaluation (several levels of evaluation):

Self-esteem;

Assessment of other groups;

Teacher assessment;

Assessment by a specially created group of experts.

1. Analysis of the quality of tea

2. Analysis of the quality of coffee

3. Analysis of the quality of cereals

4. Analysis of flour quality

5. Quality analysis pasta

6. Analysis of the quality of bread

7. Analysis of the quality of milk and dairy products

8. Quality analysis sausages

9. Quality assessment canned fish and preserves

Tea quality analysis

Objective: examine the distinguishing features different types, types of tea; to develop the ability and skills in identifying defects, preparing an average sample and examining the quality of tea .

Organoleptic assessment of the quality of tea (tea tasting).

Use the standards above to get the job done.

Examine and describe in a workbook the appearance of the pack, box, tile, brick. Use standards to get the job done. Examine and describe in a workbook the appearance of the pack, box, tile, brick.

Tea appearance (cleaning).

A sample weighing 100 g is taken from the average sample and poured into a thin layer on a sheet of white paper. The appearance of dry tea is determined by examining it in daylight (diffuse) or bright artificial light. In determining appearance dry tea pay attention to the color, evenness, uniformity and curl of the tea leaves, in tiled and brick tea check the integrity and strength of the tiles, the smoothness of the surfaces and the condition of the corners and edges.A sample weighing 100 g is taken from the average sample and poured into a thin layer on a sheet of white paper. The appearance of dry tea is determined by examining it in daylight (diffuse) or bright artificial light. When determining the appearance of dry tea, pay attention to the color, evenness, uniformity and curl of the tea leaves; in tiled and brick tea, check the integrity and strength of the tiles, the smoothness of the surfaces and the condition of the corners and edges. paper. The appearance of dry tea is determined by examining it in daylight (diffuse) or bright artificial light. When determining the appearance of dry tea, attention is paid to the color, evenness, uniformity and curl of the tea leaves; in tiled and brick tea, the integrity and strength of the tiles, the smoothness of the surfaces and the condition of the corners and edges are checked. When determining the appearance of long tea, you should also pay attention to the content of red petioles (rough stems), wood hairs, untwisted leaf blades and other impurities (small stones, fragments of glass, cement, chips, grass, etc.) in the tea.

The presence of petioles (red stems) or wood hairs in tea indicates that the tea is made from rough raw materials and is poorly sorted. The more petioles or hairs of wood the tea contains, the lower its quality.

Admixture of untwisted tea leaves negatively affects the quality of tea. Uncoiled leaves in black long tea, due to poor fermentation, retain their green color, which has a very negative effect on the aroma and taste of the tea.

Brown and reddish untwisted leaves can be found in black long tea, which is explained by the delay in processing the tea leaf, which is damaged, does not curl and does not ferment. The more brown leaves in the tea, the poorer its quality.

The admixture of foreign objects is not allowed in the tea; products clogged with foreign impurities are considered defective.

Preparation of tea infusion. Infusion, aroma and taste, color of the boiled leaf are determined after brewing the tea. To do this, weigh a sample of tea Zr with an accuracy of ± 0.1 g from a sample of 100 g and pour it into a special porcelain teapot, pour it with boiling water without refilling the teapot by 4-6 mm, cover with a lid and keep the infusion for 7 minutes for brick and 5 minutes - for other types of tea. With a shorter brewing duration, the extractive substances turn into the infusion in a smaller amount, and with a longer duration, instead of the pleasant aroma and taste of tea, the smell and taste of wood may appear.

At the end of the brewing period, the infusion is poured from the teapot into a special porcelain cup. At the same time, it is necessary to pay attention to the fact that the infusion from the teapot is completely poured out, since leaving part of the infusion in it can affect the intensity of the infusion and its extract. To do this, shake the kettle several times to completely drain the last, thickest drops of infusion. Tea analysis is carried out 1-1.5 minutes after pouring the infusion into a cup.

In the infusion of tea, its characteristics and taste are determined, and in the tea left after pouring in the teapot, the aroma and color of the boiled leaf are determined.

Infusion. When characterizing the infusion, attention is paid to its transparency, color intensity and shade. The infusion of tea should be pure; in the lower grades, turbidity is allowed. The more intensely the infusion is colored, the higher the tea is rated.

Evaluation of the infusion of black long tea is made depending on its intensity: above average, average, below average and weak. Usually the tea of ​​the highest grades has a higher average infusion. Larger leaf teas of the premium and first grade are characterized by a medium infusion, while lower grades are characterized by a weak infusion. The best is the transparent, bright color of the infusion. Brown, dark, cloudy or greenish color of black tea infusion is considered a disadvantage and indicates a violation of the technological regime. Fine tea has a more intense infusion compared to loose leaf tea.

The color of the green tea infusion should be from light green with a yellowish tint to dark yellow with a reddish tint, brick green - red-yellow, black tiled - from brown with a dark red tint to dark brown with a brownish tint, depending on the variety ...

If the color of the infusion does not meet the requirements of the standard, the tea, accordingly, receives a low rating.

Aroma and taste of tea. The aroma of tea is determined not immediately after pouring the infusion, but after 1-1.5 minutes. During this time, the boiled leaf in the teapot cools down slightly, which helps to better capture the aroma. When hot, it is impossible to detect the actual aroma of the tea. But you should also not hesitate to sample the tea for more than 1.5 minutes. The more the tea cools in the teapot, the more difficult it is to establish its aroma. If it is cooled too much (over 1.5 minutes), it is impossible to distinguish the aroma of the highest quality tea from the aroma of the inferior quality tea. Tea can have a full bouquet, delicate, delicate, pleasant or weak, rough aroma, depending on the variety.

To determine the taste, tea is drunk in small sips and the first taste sensations are recorded. The taste of the tea can be tart, not tart enough or rough, depending on the commercial grade.

The color of the boiled sheet. Place the boiled leaf on the lid of the teapot and determine its color.

The color of the boiled leaf is in direct proportion to the intensity of the infusion, aroma and taste of the tea.

When determining the color of a boiled leaf, pay attention to its uniformity: the lower the grade of tea, the less uniform the color. It can be greenish, light brown to dark green, dark brown, depending on the type and variety.

The dark color of the boiled black tea leaf is usually observed with excessive fermentation or excessive withering of the tea leaf; in case of insufficient fermentation, the color remains green. In both cases, the tea scores low.

Municipal educational institution

"Bakchar secondary school"

RESEARCH OF ORGANOLEPTIC AND CHEMICAL INDICATORS OF BLACK AND GREEN TEA

Design and research work

MBOU "Bakcharskaya secondary school", grade 11

Head: Zaitseva Lyubov Valentinovna,

Chemistry teacher.

v. Bakchar - 2016

Table of contents

1. Introduction …………………………………………………………………… 1 p.

1.1 Relevance …………………………………………… 1 p.

1.2. Purpose …………………………………………………… 1 page

1.3. Tasks ………………………………………………… 1 p.

1.4. Questioning ………………………………………… 2 p.

2. History of the emergence of tea …………………………………………… .. 4 p.

2.1. Tea in China ………………………………………………4 p.

2.2. Tea in Russia ……………………………………………… 5 p.

3. The chemical composition of tea,… .. …………………………………………… 7 p.

4. Stages of tea production ………………………………… ........................... 8 p.

5. Varieties and varieties of tea …………………………………………… .. 10 p.

6. Extraordinary facts about tea …………………………………………… .. page 14

8. Conclusion ……………………………………………………………… 19 pages 9. Sources and literature …………………………………… ……………… 20 pages

10. Appendix. Tea research ………………………………………. 21 pages

10.1. Mechanical composition of tea. ……………………………… .. Page 21

11.2 Determination of the presence of dyes ………………………… 22 p.

11.3 Organoleptic properties of tea ………………………… 23 p.

11.4. Determination of acid-base balance ……………… 23 pp.

11.5. Determination of tannin in tea …………………………………… 24 pp.

11.6. Qualitative reaction to caffeine… ………………………… 24 p.

1. Introduction.

1.1. Relevance.

A familiar way to dispel melancholy and unite the family.All over the world people know and love tea as a drink. We have seen how they cook it more than once: dry leaves are poured with boiling water. But what kind of plant is this tea?We rarely ask ourselves what this tea of ​​our "good friend" contains and how one type differs from another.Where does it grow? What are its properties? How is it used? This became interesting to me. I tried to answer these questions in my work.Nowadays, the market offers tea of ​​different quality and price, it is important to be able to understand notm and correlate quality with price,be able to chooseandthe host is correct. In the process of research, a familiar drink reveals many of its secrets.

The structure of the particles is fibrous. The color of the tea leaves is from dark green to light brown. The shape and size are different.

Individual fragments are viewed, the surface of which is covered with hairs.

Particles of dark brown color, have the same, small size. There are also light brown inclusions.

Parts of leaves and stems. The structure is homogeneous. Particle color from light brown to dark brown.

The particles are different in size and shape, the bulk is dark brown, and light brown inclusions are contained. Particle sizes from 1 mm to 6-7 mm.

Parts of leaves and stems. The structure is homogeneous. Dark brown color.

Small, dried, twisted parts of the leaves. The shape and size of the leaves are different. Color from light green to dark green, with a small amount of particles of yellow stalks.

Parts of leaves and stems The structure is homogeneous, without fibers, dark green in color.

Conclusion: As a result of examining the contents of tea with the naked eye and under a microscope, it was revealed that the heterogeneity is determined in samples No. 1, 3,4. When studying the mechanical composition under a microscope, it was revealed that sample No. 4 contains parts of leaves and a lot of parts of the stem. In sample # 1, individual fragments are visible, the surface of which is covered with hairs, which, in my opinion, have nothing to do with tea. In samples under No. 2,3, the content and size of the particles are almost the same. In sample no. 4, the leaf surface is glossy and matte.

Investigation of the presence of dyes.

Methodology: We brew tea with water at room temperature and leave for 7-10 minutes and we see that the color intensity is more pronounced in samples under No. 2,3.

Method: In the prepared warm infusion of tea, place a white cloth for 7-10 minutes, then dry it and see the difference in color.

Conclusion: The pigments and dyes contained in tea leaves can be used as safe dyes.

Add lemon wedge to the resulting tea infusions. The lemon reacted with the coloring matter of the tea, resulting in discoloration of the solutions compared to the original color. This indicates that a dye was added to these samples, and in a larger amount in samples No. 2,3.

Research on the organoleptic properties of tea.Determination of taste and aroma.

Methodology: tea is brewed for 5-7 minutes, then the aroma of the tea in pairs, taste characteristics, astringency and presence of off-flavors are compared.

Table 2.

p / p

Name of tea

Fragrance in pairs

Taste

Astringency

Foreign taste

"Princess Java" green tea with jasmine. Packaged.

Weak, sweetish, with a jasmine aroma

Weak bitterness

Weak

Grassy

"Princess Nuri" alpine, black, long tea. Packaged.

Medium, sweetish

Medium bitterness

Average

Not

"Princess Nuri" high-mountainous, long tea, black tea. Leafy, small.

Average,

sweetish

Medium bitterness

Average

Not

"Princess Java" Chinese, green, long tea. Sheet.

Weak

Weak bitterness

Weak

Grassy

Conclusion: The aroma of tea in vapor is weak in samples no. 1.4. Smell sweetish in samples no. 1,2,3.

Weak bitterness is noted in samples No. 1.4, medium - in samples No. 2,3. The degree of astringency is more pronounced in samples No. 2,3. The herbaceous aftertaste is more pronounced in samples no. 1.4.

Determination of acid-base balance.

Methodology: Strips of indicator paper were placed in the resulting tea infusion to determine pH, and then compared with a standard.

Conclusion: U green tea the pH is 6, and for black tea it is 5. The medium of the solutions is close to neutral.

Determination of tannin in tea.

Method: Add 5-6 drops of ferric chloride to the tea solution (3). In the presence of tannin in tea, the appearance of a dark purple coloration was observed.

Conclusion: Samples # 3 and # 4 have the highest tannin content.L-tanninIs a water-soluble chemical found in tea and is responsible for some of the effects that tea has on the body and condition of a person, as well as affecting the taste and aroma of tea. It is derived from an amino acid related to glutamic acid.

Determination of caffeine.

Methodology: Put 0.1 tea in a porcelain cup, add 1-3 drops of concentrated nitric acid. The mixture is carefully evaporated to dryness. As a result of the oxidation of caffeine, orange-colored tertramethylaloxanthin is formed. The analysis data is compared with the reference obtained from a citramone tablet containing 43% caffeine.

Bottom Line: Sample # 1.4 contains more caffeine. Green tea contains more caffeine than black tea. Alkaloids are an important part of any tea. It is in this group of substances that caffeine, or tea theine, is included. It is caffeine that has a tonic, stimulating effect on a person. Tea has a higher caffeine content than coffee. In addition, tea caffeine is healthier for the human body. Caffeine is found in tea leaves, and in the leaves that appeared first, its content is higher.

Table No. 3.

p / p

Name of tea

pH

The presence of tannin content

Vitamin C content.

Sample No. 1

The average

0,00009

Sample No. 2

High

Sample No. 3

High

0,00013

Sample No. 4

the average

22 +1,8

Table 3

Conclusion: Based on the studies carried out, the following conclusions can be drawn:

According to the mechanical composition, only sample No. 2 corresponds to the GOST standards, since according to the regulations, the tea leaves should not have a stem. The external heterogeneity of the composition is determined for samples No. 1,3,4.

The medium of the solutions is close to neutral. Green tea has a slightly higher pH - 6, and black tea - 5.

All tea samples contain artificial coloring,which is unacceptable, according to GOST.

Tannin is found most in loose tea compared to tea bags.

Caffeine is found in all tea samples. V large quantities it is contained in green leaf

Aroma, astringency, taste qualities teas correspond to the traditions of tea drinking in all samples.

The information indicated on tea packages is often incomplete, there is no description of the processing of tea, there is no specified time of collection, the place of tea growth.

Thus, all studied teas comply with GOST standards and can be recommended for use.

The main indicators of the quality of green tea are:

Aroma and taste of tea;

Appearance;

Infusion color;

Indicator name	GOST requirements	Sample No. 1	Sample No. 2	Sample # 3
Aroma and taste	Full bouquet, delicate delicate aroma, pleasant taste with astringency	Rough aroma, slightly perceptible tart taste	Pleasant delicate and delicate aroma, pleasant strongly tart taste	Pleasant aroma, slightly perceptible taste.	Rough aroma, slightly perceptible tart and bitter taste.
Infusion	Transparent, light green, with a yellowish tinge	Dark yellow with a reddish tinge, unclear	Transparent light green with a yellowish tinge	Dark yellow. Turbid with sediment	Dark yellow, cloudy.
Boiled leaf color	Uniform, with a greenish tint	Heterogeneous, dark yellow	Uniform with a greenish tint	Heterogeneous, dark yellow	Heterogeneous, dark yellow.
Appearance	Smooth, uniform, well-curled	Uneven, poorly twisted tea leaves	Smooth, homogeneous, twisted, free of impurities	Uneven, there are impurities: sticks, branches.	Leafy, uneven, poorly twisted tea leaves with foreign impurities

The requirement for organoleptic characteristics of green tea in accordance with GOST

Appearance of tea infusion: - leafy and granular; - pressed;	Light yellow or light green, transparent or dull; Red yellow
Aroma and taste of tea infusion: - leafy and granular; - pressed	Delicate aroma, pleasant taste with astringency; Peculiar to green pressed tea
Boiled tea leaves color: -leaf and granular; - pressed	Uniform, with a yellowish and greenish tint Dark green with a dark brown tint
Appearance of tea: -leaf -granulated; - pressed	Homogeneous, even, twisted Fairly even, spherical or oblong shape Dark green pressed tiles, smooth surface, even edges

Sampling and quality assessment

Sample No. 1. Greenfield green tea, bouquet variety, large-leaf, net weight 100g, manufacturer: LLC "Orimi Trade".

Sample No. 2. Tess lime. Long green tea with citrus zest, flower petals and lime scent in bags. Ingredients: long green tea, lemon sorghum, rose hips, citrus peel, calendula petals, natural lime flavor. Manufacturer: LLC "NEP".

Sample No. 3. Flavored green tea LIPTON.

Ingredients: long green tea, osmanthus and pear flavor. Manufactured by LLC "Unilever Rus"

Marking	GOST requirements	Actually	Conformity
Sample No. 1.	Name Variety Date of manufacture Composition Net weight Designation of the standard Expiry date	+ + + + + + +	This sample meets the requirements of GOST in all respects
Sample No. 2	Name Variety Date of manufacture Shelf life Composition Net weight Designation of the stardom Expiry date	+ - + + + + + +	This sample does not correspond to GOST in one indicator (the grade is not indicated on the packaging)
Sample No. 3	Name Variety Date of manufacture Shelf life Composition Net weight Standard designation Shelf life	+ - + + + + + +	This sample does not correspond to GOST in one indicator (the grade is not indicated on the packaging)

Conclusion: In samples No. 2 and No. 3, the type of tea is not indicated. Sample №1 corresponds to GOST in all respects, №2 and №3 also correspond to GOST and belong to the third grade.

Conclusion

Green tea, which until recently was considered an oriental exotic, is gaining more and more popularity among tea lovers. In Russia, back in the 17th-18th centuries. green tea brought from China was quite widespread, but then it was replaced by black tea.

Green and black tea are made from the same tea leaves, but the difference in their production technology determines their different biological value and taste. To obtain green tea, the raw material is subjected to heat treatment, in which the enzymes of the tea leaf are killed, which makes it possible to preserve the substances contained in the tea leaf from oxidation. Therefore, according to chemical composition green tea is closer to the "natural" tea leaf. It does not form dark-colored phenolic compounds. Green tea is very rich in vitamins . In my coursework, I studied the assortment of green tea in the Magnit and Dixy stores, I learned that these stores have a fairly wide range of green tea. I found out that the main manufacturers on the market are: LLC "Orimi Trade"; LLC "Uniliver Rus"; LLC "NEP"; LLC SDS-FOODS; LLC "Baltic Resource". Then I studied the main indicators of green tea, made a selection of samples of the main manufacturers for comparative characteristics. I also studied the organoleptic indicators of green samples I selected, we can make the following conclusion: in samples No. 2 and No. 3, the type of tea is not indicated. Sample №1 corresponds to GOST in all respects, №2 and №3 also correspond to GOST and belong to the third grade. Having studied the assortment of tea, I found out that a huge number of tea manufacturers are competing in the world market, and the assortment of commercial teas is constantly being updated and expanded.

Tea quality indicators. Various methods of laboratory research (chemical and luminescent analyzes, gas chromatography and spectrometry, etc.) are used to assess the quality of tea, conduct an examination and in-depth study of its properties.

However, the organoleptic research of tea is still decisive in assessing its quality.

Organoleptic properties of tea are determined by experts in the field tasting evaluation- titters using a 10-point system (see table 7). According to this system, the lowest-grade teas (domestic and foreign) are estimated at only 1.5 points, and the highest-quality ones - at 5.5 points and higher. A tea score of 8-10 points is still considered unattainable. The highest quality teas, called Unique (for example, the best teas samples Indian Darjeeling tea or Ceylon Nyur-Eli), very rarely receive a score of up to 7 points for their unique aroma and taste. The evaluation of the usual higher grades is much lower. So, the highest grade of the I category of factory tea can have a score of 6.25-8.00, the highest grade of the II category (B-2) - 5.25-6.0, and the 1st grade - 4.75-5, 0.

Organoleptic method tea evaluation is so far the only express method that allows one to determine the entire set of tea properties within 1-2 minutes.

According to GOST, the organoleptic assessment of tea is carried out according to the following indicators: aroma and taste, transparency and intensity of infusion, color of the boiled leaf, appearance (harvesting) of dry tea.

To test the quality of 3 g of tea, 130 ml of freshly boiled water with a pH of 6-7 is poured into a teether teapot and covered with a lid. After a 5-minute infusion (brick tea is infused for 7 minutes), the extract without tea leaves is poured into a special white porcelain cup and the color and intensity of the infusion are determined. The color of the infusion gives an idea of ​​the type of tea (black, green, yellow, red) and its varieties (brick and slab tea differ from baikh tea in the specific color of the infusion). When assessing the color of the infusion, attention is paid to its correspondence to the type of tea, density, intensity, brightness. Bright color and always accompanying transparency are a reliable sign of high quality tea, which cannot be said about color. Pressed teas do not give a bright infusion due to the large amount of suspended particles in them. A dark, densely colored, but dull opaque infusion is a sign of poor quality tea. In an alkaline environment, the brightness and transparency of the tea infusion disappear and a brown color appears.

To determine the taste, a little tea is sipped from a cup, and, without swallowing, rolled in the mouth, evaluating the taste sensations. The astringency and fullness of the taste of the infusion are signs of high extractability of teas, their high P-vitamin activity. If the astringency is not sufficiently pronounced, the tea has an "empty", "flat" taste characteristic of over-fermented teas.

The most important indicator of the quality of the infusion is its aroma, which is formed in the first one and a half to two minutes after brewing. Aromatic substances are concentrated in the foam on the surface of the infusion. Due to the volatility of the tea essential oil The aroma of the infusion should be determined no later than 5 minutes after the infusion, that is, immediately after draining the infusion. To do this, the kettle with the boiled leaf remaining in it is brought to the nose and, strongly drawing in air, the smell is assessed. In tetester practice, a special terminology has been adopted to determine the aroma of benign tea: rosaceous, almond, honey, citrus, a mixture of aromas of strawberries, geraniums and black currants, etc. Organoleptically, undesirable odors are also detected in the aroma of tea, which are the result of a violation of technology or improper storage: smoke, hotness, herbaceous odor, dampness, mustiness, mold, acid and various odors.

A reliable idea of ​​the quality of tea is given by the assessment of the color of the boiled leaf. To do this, turn the teapot over on the lid and, squeezing the remaining infusion from the boiled leaf, determine the color of the leaves and the uniformity of their color. High quality black long tea has a boiled leaf that has a bright copper color. Dark brown, green and dull shades of the boiled leaf color are considered defects.

To assess the appearance, average samples are poured onto clean sheets of paper and visually determine the May group (leafy or small), the uniformity of color and the degree of curl of the tea leaves, the presence of tips (golden tips - flash buds), indicating high quality tea, the presence of stems and tea dust, typical for low varieties of teas from the raw materials of late autumn collection.

When assessing the quality of tea according to the current standard, moisture, mass fraction of water-soluble extractives, metal impurities are also determined. For a more complete characterization, in addition to standard indicators, ash content, the content of caffeine, tannin and other components are determined.