GB/T 8305-2013Tea -- Determination of water extracts content (English PDF)

Foreword

This standard was drafted in accordance with GB/T 1.1-2009 given rules.

This standard replaces GB/T 8305-2002 "Determination of tea extract." This standard compared with GB/T 8305-2002, Technical Changes are as follows.

--- Modify the repeatability requirement. not exceeding 0.5g per 100g sample modified to repeat the same sample obtained under the conditions of measurement the absolute difference between the results should not exceed 2% of the arithmetic mean.

This standard uses redrafted law revision using ISO 9768:1994 "Determination of tea extract." This standard and ISO 9768:1994 Compared to the main technical differences are as follows.

--- With boiling water bath heating instead of direct heating furnace extraction, in order to improve the uniformity, stability;

--- Baking dish and filter paper drying temperature 103 °C modified to 120 °C ± 2 °C;

--- Repeatability. absolute error between two-sample test results is less than 1%, revised as measured under the same conditions repeated sample obtained the absolute difference between the results should not exceed 2% of the arithmetic mean;

--- Removed 10.2 reproducibility;

--- Remove the ISO 9768:1994, Chapter 11 test reports;

--- Remove the ISO 9768:1994 Annex A laboratory comparison results.

This standard also made the following structural modifications.

--- International standard Chapter 6 sampling, sample preparation Chapter 7, 8, respectively, measured steps to modify this standard 6.1,6.2,6.4;

--- International standard 10.1 repetitive modify this standard 7.2.

This standard also made the following editorial changes.

--- Remove the ISO 9768:1994 Foreword.

The standard proposed by China Federation of Supply and Marketing Cooperatives.

This standard by the National Standardization Technical Committee of tea (SAC/TC339) centralized.

This standard was drafted. China Federation of Supply and Marketing Cooperatives Hangzhou Tea Research Institute, the National Tea Quality Supervision and Inspection Center.

1 Scope

This standard specifies the tea water extracts measurement instruments and equipment, methods of operation and the result of the calculation methods.

This standard applies to tea flooding Spectroscopy.

2 Normative references

The following documents for the application of this document is essential. For dated references, only the dated version suitable for use herein Member. For undated references, the latest edition (including any amendments) applies to this document.

GB/T 8302 sampling Tea (GB/T 8302-2013, ISO 1839. 1980, NEQ) GB/T 8303 Tea grated dry matter content of the sample preparation and measurement (GB/T 8303-2013, ISO 1572. 1980, MOD)

3 Terms and Definitions

The following terms and definitions apply to this document.

Water extract waterextracts Under specified conditions, the leaching of tea with boiling water soluble substances.

Principle 4

Extraction with boiling water reflux tea water-soluble substance, and then filtered, washed, dried, weighed tea leaves after extraction, calculate water extract content.

5 Apparatus and appliances

5.1 blast electric oven. temperature 120 °C ± 2 °C.

5.2 boiling water bath.

5.3 Buchner funnel with the vacuum filtration apparatus.

5.4 Quality aluminum or glass baking dish. a cover, an inner diameter of 75mm ~ 80mm.

5.5 dryer. containing more effective desiccant.

5.6 Analysis of balance. a sense of the amount of 0.001g.

5.7 conical flask. 500mL.

5.8 mill. the material does not absorb moisture made; dead as small as possible, easy to clean; interior aperture of 3mm sieve.