JPH03179239A - Evaluation of quality and processing of green tea leaf - Google Patents

Abstract

PURPOSE:To enable accurate evaluation of quality and manufacture of a product with a stable quality by a method wherein green tea leaf is dried below a fixed moisture level and a content component thereof is measured by a near infrared spectrochemical analysis while a specified production process is determined by the resulting content of the green tea leaf. CONSTITUTION:A green tea leaf (sample) is sampled and dried to reduce until moisture is down below 20% and then, it is crushed to be adjusted in particle size with a sieve ranging from 0.4-0.2 mm. Then, the sample is irradiated with near infrared rays by a near infrared spectrochemical analyzer to determine absorptivity thereof and a content component, a characteristic value or a sensory quality of a green tea leaf from the absorptivity thus obtained. Moreover, manufacturing methods for a rough tea process and a firing process as production process of tea are determined by the content component of the green tea leaf. With such an arrangement, objective evaluation of quality is possible free from external factors, which moreover, facilitates accurate section of a production process to match an amount of components contained actually and a desired product. This enables a producer to evaluate quality accurately and a manufacturer to turn out a product with a stable quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for evaluating the quality of green tea leaves, which measures the components, characteristic values, or sensory quality of tea by near-infrared spectroscopy, and a method for processing the same.

[Conventional technology]

Sensory evaluation methods have traditionally been used to evaluate the quality of tea. In other words, it was an examination method that relied on human sensibility and required a sensitive and skilled examiner.

This sensory evaluation method relied on the five human senses, and it was inevitable that the results of the examination would be greatly influenced by the physical condition and environment of the person conducting the examination, and it could not be called an objective examination method. There is also some direction toward incorporating component analysis performed using chemical methods, but this has not yet been established.

[Problem to be solved by the invention]

As is clear from the above-mentioned prior art, examination methods that rely on human senses not only cannot be accurately expressed numerically, but are also influenced by differences in the examiner's subjectivity.

Therefore, it has become necessary to incorporate chemical evaluation into sensory evaluation when trading tea and setting standards for it. In other words, in order to judge tea fairly, it is desirable to evaluate it from both sensory and chemical aspects, and to express the quality of tea as objectively as possible.

In addition, chemical testing methods generally require testing equipment such as a color difference meter, spectrophotometer, gas chromatography, or liquid chromatography, and this requires a sufficient number of testing personnel. It is not possible for anyone to easily provide personnel and equipment anywhere.

In addition, in the case of rough tea processing and finishing (pastoring) processing companies, the processing methods (drying time, drying temperature, steaming temperature, steaming time, pasteurizing temperature, pasteurizing time, etc.) are determined based on the variety, picking time, appearance, etc. of the raw tea leaves. There is a lot of reliance on intuition, and the selection of teas (Sencha, Gyokuro, Haushicha, etc.)
Because of the more detailed steps involved, it was inevitable that the finished product would vary.

Based on the above, the technical problem of the present invention is to develop a method for evaluating the quality of tea leaves and a method for processing the same, which allows anyone to easily examine the quality of tea with a minimum number of people without relying on sensory evaluation. be.

[Means for Solving the Invention] The above-mentioned technical problem is solved by drying and pulverizing fresh tea leaves to a moisture content of 20% or less, and measuring the contained components, characteristic values, or sensory quality of the fresh tea leaves by near-infrared spectroscopy. It was used as a means to solve the problem.

Furthermore, the method of processing the rough tea process and the pasteurization process, which are the tea manufacturing processes, was determined based on the ingredients contained in the fresh tea leaves, thereby providing a means for solving the above-mentioned technical problem.

[For production]

Tea leaf analysis using near-infrared spectroscopy can be done as long as the raw tea leaves that have been harvested can be analyzed as they are, but if the raw tea leaves have a high moisture content, it is difficult to crush them during the simple crushing process performed during analysis. In particular, Ichibancha, which is said to have the best quality, has young tea buds, and the raw tea leaves that are used for Gyokuro are grown under cover, so they have less coarse fiber and are softer.
Because tea leaves are composed of water, it is difficult to grind them as is, and it is necessary to dry the fresh tea leaves to below a certain moisture content.

In the present invention, since the powder is dried to a moisture content of 20% or less and then pulverized, the above-mentioned problem is solved and the pulverized particle size becomes uniform. Among the ingredients contained in fresh tea leaves, the enzymes are inactivated by the drying heat, so there is almost no change during drying and the taste components are the same as the raw tea leaves.

Next, the ground tea (sample) is analyzed using near-infrared spectroscopy, and the values obtained include the contained components, characteristic values, and sensory quality.

In general, in near-infrared spectroscopy, the absorbance obtained by irradiating a crushed sample with near-infrared rays forms a unique absorbance curve depending on the components contained in the sample, and shows a curve unique to the sample. Calculate the component values contained in the sample by comparing the values obtained from the sample with other samples or reference samples in the narrow band wavelength region, or determine the component values by comparing the values obtained by the second derivative of the absorbance curve. or

In addition, the components of fresh tea leaves obtained by near-infrared spectroscopy are proteins, carbohydrates, amino acids, lipids, water, sugars,
It has fiber content, alcohol, caffeine, etc.

Among the chemical components of tea, those particularly related to quality include nitrogen, amino acids, caffeine, protein, starch, and lipids. The production of these chemical components depends on the variety of tea, tea harvesting,
The quality of the tea is determined by the arrangement of the tea buds, the growing soil, and the growing environment (temperature, soil temperature), and the quality of the tea is determined before the manufacturing process is established, which is determined by the variety, the appropriate timing of tea, and the product brand, such as rough tea processing and finishing processing. are doing.

In other words, the taste components of tea are determined at the time of picking, and the absolute amounts of the components do not change during the manufacturing process such as rough tea processing, but the amount extracted changes.

The table below shows the absolute amount of the components and the amount of component extracted after an arbitrary period of time when the same raw leaves are rolled into gyokuro in the crude tea processing process and when they are made into tencha without rolling.

Therefore, even with the same raw material, it changes into Gyokuro and Tencha in the raw tea process, so the quality of the tea should be determined at the raw leaf stage, and the quality of the tea should be determined at the raw leaf stage. Good or bad should be determined.

In view of the above, the present invention makes it possible to dry and crush fresh tea leaves, facilitate the analysis of tea components through crushing, and perform near-infrared spectroscopy without going through the stages of rough tea processing and finishing. We have made it possible to analyze the components of fresh tea leaves using a method that can be easily carried out by pulverizing the sample. The values obtained in this component analysis are the contained components, and the characteristic values of aroma, flavor (bitterness, astringency, umami, hot taste), and light blue formed by these values can be arbitrarily determined using methods such as multiple regression analysis. It is also possible to obtain it based on an assumed manufacturing process. Furthermore, it is also possible to evaluate the quality of tea, for example, by scoring, directly from the contained components or from characteristic values.

Conversely, it is also possible to use the above-mentioned contained components, characteristic values, or quality evaluation values as a guideline for determining the steaming temperature, time, kneading time, temperature, etc. in the manufacturing process, and from the producer's perspective,
Fair quality evaluation can be carried out on fresh leaves, and
Processors are now able to make various adjustments to the manufacturing process based on quality evaluations to produce products that consumers prefer.

〔Example〕

An example of the method for evaluating the quality of raw tea leaves of the present invention will be described.

First, the steps for quality evaluation are as follows: ■Sampling the sample (fresh tea leaves).

■ Dry the sample and reduce the moisture content to 20% or less.

(2) Grind the sample and use a sieve of 0.4+nm -0.2mm to make the particle size uniform.

■Irradiate near-infrared rays with a near-infrared spectrometer to determine absorbance.

■Determine the content, characteristic values, or sensory quality of the fresh tea leaves from the determined absorbance.

becomes. Next, each procedure will be explained.

For sampling, collect 100 g or more from the picked green tea leaves using a quartering method or the like. This is 70% to 80% of raw tea leaves.
This is because % is water, and this water is largely removed by drying. In the example of Sencha, fresh tea leaves account for approximately 350% on a dry basis.
It has been revealed that it has a water content of

In addition, the sampled raw tea leaves must be sorted in advance to avoid contamination with words and stems that are removed during rough tea processing and finishing processing. This is because words contain many bitter substances such as tannins, and if they are mixed into a product, the grade will be lowered, so they are generally sorted before being made into a product.

The collected sample is then dried. Drying temperature is 70℃~10
The temperature is generally 70°C to deactivate the enzyme.
or higher temperature is required. At this time, the target moisture value is 20% or less on a dry basis. When the water content exceeds 20%, even if the same sample has the same water content, as shown in FIG. 1, there will be a difference in the absorbance for each wavelength analyzed, and the correlation with the determined value will be low. This is a difference in the particle size distribution of the sample after crushing due to high moisture content, and is a point to be kept in mind in near-infrared spectroscopic analysis methods that are affected by the particle size of the sample. The present invention solves this problem by drying the sample to a constant moisture content of 20% or less, making stable near-infrared spectroscopic analysis possible.

The sample dried to less than 20% is then crushed using a crusher. However, since crushers that increase the sample temperature due to crushing change the moisture content of the sample, we recommend using a crusher that does not increase the temperature of the sample due to crushing, such as a cyclone. A crusher etc. is good. At this time, in order to make the pulverized particle size uniform, the
By passing through a sieve of m, the sample to be analyzed by near-infrared spectroscopy will have a more stable particle size distribution.

Next, the sample, which has become the pulverized particles, is analyzed using a near-infrared spectrometer. In this analysis, a sample is evenly filled into a measurement cell with a quartz glass lid and irradiated with near-infrared light. The sample is irradiated with near-infrared light (I100 nm to 2500 nm) through quartz glass, and the reflectance R is determined by the ratio of the diffuse reflection energy of a separately provided white ceramic plate and the diffuse reflection energy of the sample, and is calculated as lQg (1/ R) value is the absorbance. The near-infrared light irradiated at this time is lI00nm ~
There are methods such as continuous irradiation at 2500 nm, or irradiation using multiple specific wavelengths using narrow band filters, but it goes without saying that measurements can be made in a short time by irradiating only specific wavelengths using multiple filters. . However, in order to determine the specific wavelength, it is necessary in advance to continuously irradiate wavelengths and find the specific wavelength that hits the desired content component.

Perform multiple regression analysis using multiple log(1/R) values obtained by near-infrared spectroscopy and values obtained from other chemical analyses, etc.
By calculating the coefficient (F) of each log(1/R1 value), for example, among the contained components, nitrogen is nitrogen -Fn +F+ ・
log(1/R), +F2・log(1/R) 2
+-xr. −log(1/R). A calibration curve is established by the multiple regression equation (1), and the amount of nitrogen can be determined by substituting the log(1/R) value determined by near-infrared spectroscopic analysis. other amino acids, caffeine, protein,
Similarly, for ingredients such as starch and lipids, multiple regression formula % formula % Next, characteristic values such as aroma, nourishment (bitterness, astringency, umami, sweetness), light blue, etc. are formed by the above-mentioned ingredients. Therefore, a multiple regression equation is established using each ingredient obtained from the log(1/R1 value or log(1/R) value using the multiple regression equation (1)) and the sensory evaluation values (aroma, flavor, light blue). Find the coefficient, for example, Degustation - Gn + G+ ・log (
1/R)t + G2 ・log(1/R) 2 +
... 10G.・log(1/R)
. ... Obtain the multiple regression equation of 2). Or, if the ingredients related to nutrition are nitrogen and amino acids, then nutrition = Ho + H + ・Nitrogen quantum H, amino acids ・
...(3) Obtain the multiple regression equation. In this case, the multiple regression equation (3) using the log (1/R+ cow obtained from the value and the r test value) is the multiple regression equation (
The correlation coefficient is inferior to that of 2).

Furthermore, in terms of quality, the log (1/RJ value or contained component or characteristic value and the grade or +
A multiple regression equation is established based on the scores of t and '+6-a examination. Because it is calculated from the calibration curve obtained from the content, characteristic value, or presymptomatic quality (4, always obtained using each multiple regression equation!) and the 'g(+/R) value, the external 1,
Seven companies are now able to obtain stable values that are not influenced by 1.

Furthermore, the values obtained here are obtained from raw tea leaves, and can be used as important information for determining the processing temperature and processing time of the rough tea process and finishing (pastoring) process in the subsequent steps.

``Effects'' Until now, the mainstream of tea evaluation has been based on the appearance and sensory evaluation of raw tea leaves, but with the present invention, by analyzing the ingredients themselves, it has become possible to objectively evaluate quality unaffected by external factors. Furthermore, the work is simple, and standardization allows anyone to perform quality evaluation, and does not require a large amount of testing equipment.

In addition, the manufacturing process for rough tea processing and finishing is determined based on intuition such as the variety of fresh tea leaves, the time of picking, and the appearance, not on the ingredients contained, and the method that is appropriate for the tea being produced (sencha, gyokuro, haujicha, etc.) is adopted. Therefore, it was inevitable that variations would occur in the actual product, but by knowing the ingredients contained, it would be easier to reliably select a manufacturing process that matches the actual amount of ingredients contained and the desired product. It became.

As a result of the above, it has become possible for producers to accurately evaluate quality and for processors to manufacture products with stable quality.

[Brief explanation of drawings]

FIG. 1 is an absorbance curve diagram when raw tea leaves with a moisture content of 20% or more are analyzed by continuous spectrum.

Claims (2)

[Claims] (1) A method for evaluating the quality of green tea leaves, which comprises drying the green tea leaves to a moisture content of 20% or less, pulverizing them, and measuring the contained components, characteristic values, or sensory quality of the green tea leaves by near-infrared spectroscopy. (2) A method for processing fresh tea leaves, characterized in that the processing methods of the rough tea process and pasteurization process, which are tea manufacturing processes, are determined by the ingredients contained in the fresh tea leaves.