Foreword
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This standard replaces GB 31604.7-2016 National food safety standard - Food contact materials and articles - Decolorization test.
The following main changes have been made with respect to GB 31604.7-2016:
——the clause "Scope" has been modified;
——the clause "Principle" has been modified;
——the clause "Reagents and materials" has been added;
——the clause "Instruments and equipment" has been added;
——the clause "Analysis steps" has been modified;
——the clause "Expression of results" has been modified.
National food safety standard -
Food contact materials and articles - Decolorization test
1 Scope
This standard specifies the decolorization test method for food contact plastic materials and articles.
This standard is applicable to the determination of soaking coloring and wiping decolorization of food contact plastic materials and articles with colorants.
2 Principle
Decolorization test is divided into two parts: soaking coloring and wiping decolorization. The food simulants or chemical alternative solvents obtained from migration test are adopted for soaking coloring, and grey scale for staining or 9-Step Chromatic Transference Scale is used to evaluate the coloring grade by soaking. In wiping decolorization, absorbent cotton wetted and saturated by food simulants is adopted to wipe the food contact surface of the specimen, and grey scale for staining or 9-Step Chromatic Transference Scale is used to evaluate the coloring grade of absorbent cotton after wiping.
3 Reagents and materials
Unless otherwise specified, analytically-pure reagents and Class-II water specified in GB/T 6682 are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Glacial acetic acid (C2H4O2).
3.1.2 Anhydrous ethanol (C2H6O).
3.1.3 Isooctane (C8H18).
3.1.4 95% ethanol.
3.1.5 Vegetable oil (olive oil, corn oil): meeting the requirements of GB 5009.156.
3.1.6 Coconut oil (CAS No. 8001-31-8): chemically pure.
3.2 Preparation of reagents
Food simulants: prepared in accordance with GB 5009.156.
3.3 Materials
3.3.1 Absorbent cotton: white.
3.3.2 Grey scale for staining: meeting the requirements of GB/T 251 (see Figure A.1 in Annex A).
3.3.3 9-Step Chromatic Transference Scale: meeting the requirements of American Association of Textile Chemists and Colorists (AATCC) standard (see Figure A.2 in Annex A).
3.3.4 Colorimetric tube with stopper: 50mL, colorless, only full and half colorless scale marks.
Foreword i
1 Scope
2 Principle
3 Reagents and materials
4 Instruments and equipment
5 Analysis steps
6 Expression of results
Annex A Typical diagrams of grey scale for staining and 9-Step Chromatic Transference Scale
