GB/T 8314-2002 Determination of total free amino acids in tea

This standard specifies the principle, instruments and utensils, reagents and solutions, operation methods and result calculation methods for the determination of the total amount of free amino acids in tea. This standard is applicable to the determination of the total amount of free amino acids in tea. GB/T 8314-2002 Determination of the total amount of free amino acids in tea GB/T8314-2002 Standard download decompression password: www.bzxz.net

GB/T8314-2002
Determination of total free amino acids. This standard is a revision of GB/T8314-1987 "Tea
This standard is revised mainly in accordance with the requirements of GB/T1.11993 "Guidelines for Standardization Work Unit 1: Rules for Drafting and Presentation of Standards Part 1: Basic Regulations for Standard Writing", and some modifications have been made to GB/T8314-1987 in terms of format and text, but the specific technical content has not changed.
This standard will replace GB/T8314-1987 from the date of implementation. This standard was proposed by the All-China Federation of Supply and Marketing Cooperatives. This standard is under the jurisdiction of the Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The drafting unit of this standard: Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The main drafters of this standard: Zhou Weilong, Sun Anhua, Zhong Luo. The Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives is responsible for the interpretation of this standard. 152
1 Scope
National Standard of the People's Republic of China
Determination of total free amino acids in tea
Tea---Determination of freeamino acids contentGB/T 8314—2002
Replaces GB/T83141987
This standard specifies the principle, instruments and utensils, reagents and solutions, operation methods and result calculation methods for the determination of the total free amino acids in tea.
This standard is applicable to the determination of the total free amino acids in tea. 2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8302—2002 Tea sampling
Preparation of ground sample and determination of dry matter content GB/T 8303—-2002
GB/T 8312—2002
Determination of caffeine
GB/T 8313--2002
Determination of tea polyphenols
3 Definitions
This standard adopts the following definitions.
Free amino acidsfree amino acids
Organic acids with α-amino groups that exist in a free state in tea water extract. 4 Principle
α-Amino acids are heated with benztrione at pH 8.0 to form a purple complex, and its content is determined by spectrophotometry at a specific wavelength.
5 Instruments and appliances
Routine laboratory instruments and the following items:
5.1 Analytical balance: sensitivity 0.001g.
5.2 Spectrophotometer.
6 Reagents and solutions
The reagents used should be analytical grade (AR), and the water should be distilled water. 6.1 pH 8.0 phosphate buffer: According to the provisions of 6.2 in GB/T8313--2002, prepare 1/15mol/L disodium hydrogen phosphate (6.2.1) and 1/15mol/L potassium dihydrogen phosphate (6.2.2) solutions. Then take 95ml of 1/15mol/L disodium hydrogen phosphate solution and 5ml of 1/15mol/L potassium dihydrogen phosphate solution and mix them well.
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on June 17, 2002, implemented on December 1, 2002
GB/T 8314—2002
6.22% hydration triketone solution: weigh 2g of hydrated triketone (purity not less than 99%), add 50mL of water and 80mg of stannous chloride (SnCl22H0)) and stir evenly. Add a small amount of water to dissolve in a dark place for day and night, filter and add water to make up to 100mL. 6.3 Theanine or glutamic acid standard solution: weigh 100mg of theanine or glutamic acid (purity not less than 99%) and dissolve it in 100mL of water as the mother solution. Accurately aspirate 5ml of the mother solution and add water to make up to 50mL as the working solution (1ml. Contains 0.1mg of theanine or glutamic acid). 7 Operation method
7.1 Sampling
According to the provisions of GB/T8302.
7.2 Sample preparation
According to the provisions of GB/T8303.
7.3 Determination steps
7.3.1 Preparation of test solution
According to the provisions of 11.1 of GB/T8312-2002. 7.3.2 Determination
Accurately pipette 1mL of test solution (7.3.1) and inject it into a 25mL volumetric flask, add 0.5mL pH 8.0 phosphate buffer (6.1) and 0.5mL 2% benzyltrione solution (6.2), and heat in a boiling water bath for 15min. After cooling, add water to make up to 25mL. After standing for 10min, use a 5mm colorimetric cup to measure the absorbance (A) at 570nm with the reagent blank solution as reference. 7.3.3 Preparation of amino acid standard curve
Pipette 0.0, 1.0, 1.5, 2.0, 2.5, 3.0 mL of amino acid working solution (6.3) into a set of 25 mL volumetric flasks, add 4 mL of water, 0.5 mL of pH 8.0 phosphate buffer (6.1) and 0.5 mL of 2% triacetin solution (6.2) to each flask, heat in a boiling water bath for 15 min, cool and add water to make up to 25 mL. Measure the absorbance (A) according to the procedure in 7.3.2. Draw a standard curve with the measured absorbance and the corresponding theanine or glutamic acid concentration.
8 Calculation of results
8.1 Calculation method
The free amino acid content in tea is expressed as dry mass fraction and calculated according to formula (1): C
Total amount of free amino acids (calculated as theanine or glutamic acid) (%) Where: L——
Total amount of test solution, mL;
LAmount of test solution for determination, mL;
Amount of sample, g,www.bzxz.net
C—Milligrams of theanine or glutamic acid obtained from the standard curve according to the absorbance determined in 7.3.2; m
Sample + substance content, %.
..-(1)
If the requirement of repeatability (8.2) is met, the arithmetic mean of the two determinations shall be taken as the result, and the result shall be rounded to one decimal place. 8.2 Repeatability
The difference between two measured values ​​of the same sample shall not exceed 0.1g per 100g of sample: 151
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