This standard specifies the principle, instruments and utensils, operation methods and result calculation methods for the determination of moisture content in tea. This standard is applicable to the determination of moisture content in tea. GB/T 8304-2002 Determination of moisture content in tea GB/T8304-2002 Standard download decompression password: www.bzxz.net

GB/T8304bzxZ.net
1-2002
This standard is equivalent to adopting ISO1573:1980 "Determination of mass loss of tea at 103°C" and revising GB/T83041987 "Determination of moisture content in tea". The main difference between this standard and ISO1573:1980 is that the drying time of the sample is changed from 6h to 4h in the moisture determination by 103°C gravity method.
The main difference between this standard and GB/T8304-1987 is that 1. The sample for moisture determination is modified from ground sample to non-ground sample (except for compressed tea). 2. The 120℃ drying method is added to the moisture determination method. This standard replaces GB/T8304-1987 from the date of implementation. This standard is 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 position of this standard: Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The main drafters of this standard are Sun Anhua and Zhou Weilong. This standard is interpreted by the Hangzhou Tea Research Institute of the China National Federation of Supply and Marketing Cooperatives. 113
GB/T8304—2002
ISO Foreword
ISO) (International Organization for Standardization) is an international alliance of national standardization organizations (ISO member groups). Usually, the work of formulating international standards is undertaken by ISO technical committees. Each member group has the right to become a representative of the project committee if interested, and official or unofficial international standard organizations associated with ISO also participate in the work. ISO and the International Electrotechnical Commission (IEC) work closely on electrotechnical standard documents.
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International Standard ISO1573 was formulated by ISO/TC34 Agricultural Products Technical Committee. 114
1 Scope
National Standard of the People's Republic of China
Determination of moisture content in tea
Tea Determination of moisture contentGB/T 8304—2002
eqvISo1573:1980
Replaces GB/T8304--1987
This standard specifies the principle, instruments and utensils, operation methods and calculation methods for the determination of moisture content in tea. This standard is applicable to the determination of moisture in tea. 2 Referenced 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
GB/T8303--2002 Preparation of ground tea samples and determination of ten substances in them 3 Definitions
This standard adopts the following definitions.
Moisture content
The mass loss of a sample when heated to constant weight at a specified temperature under normal pressure. 4 Principle
The sample is heated to constant weight in an electric constant temperature drying oven at 103°C ± 2°C and weighed. Instruments and appliances
Conventional laboratory instruments and the following items:
5.1 Aluminum drying oven: with lid, inner diameter 75mm~80mm. 5.2 Blast electric constant temperature drying oven: can automatically control the temperature ± 2°C. 5.3 Dryer: contains effective desiccant.
5.4 Analytical balance: sensitivity 0.001g.
6 Operation method
6.1 Sampling
Sampling shall be carried out in accordance with the provisions of GB/T8302.
6.2 Sample preparation
Prepare the tea sample according to the provisions of 6.2.2 of GB/T8303-2002 for compressed tea. For tea other than compressed tea, mix the sample according to the sampling operation in 6.1.
6.3 Preparation of aluminum baking dish
Put the clean baking dish with the cover in a drying oven at 103°C ± 2°C, heat for 1 hour, cover it and take it out, cool it to room temperature in the desiccator, and weigh it (accurate to 0.001g). Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on June 17, 2002 and implemented on December 1, 2002.
6.4 Determination steps
6.4.1 Method 1 - 103℃ constant weight method (arbitration method) GB/T8304-2002
Weigh 5g (accurate to 0.001g) of sample (6.2) in a drying oven (6.3) of known mass, and place it in a 103℃±2℃ drying oven (5.2) (III cover is placed on a tilted dish). Heat for 4h, cover and take out, cool to room temperature in the desiccator (5.3), and weigh. Heat in the drying oven for another 1h, cover and take out, cool in the desiccator, and weigh (accurate to 0.001g). Repeat the heating operation for 1h until the difference between two consecutive weighings does not exceed 0.005g, which is constant weight, and the minimum weighing shall prevail.
6.4.2 Second method
-120℃ drying method (quick method)
Weigh 5g (accurate to 0.001g) of sample (6.2) into a known mass of aluminum drying blood (6.3), and place it in a 120℃ drying oven (5.2) (III lid is placed on a tilted dish). Calculate the time when it returns to 120℃ within 2min, heat for 1h, cover and take out, cool to room temperature in the dryer (5.3), and weigh (accurate to 0.001g).
Result calculation
7.1 Calculation method
The moisture content of tea is expressed as mass fraction and calculated according to formula (1). M,-M2× 100
Moisture content (%)=
Where: M,-mass of sample and aluminum drying blood before drying, g; M,-mass of sample and aluminum drying blood after drying, g, M.-mass of sample, g.
If the repeatability requirement (7.2) is met, the arithmetic mean of the two measurements shall be taken as the result (keep one decimal place). 7.2 Repeatability
The difference between the two measurements of the same sample shall not exceed 0.2g per 100g. Note: When the second method is used to determine the moisture content of tea, if the repeatability requirement is not met, the first method shall be used for determination. 116
(1)
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