GB 31604.7-2023National food safety standard - Food contact materials and products - Decolorization test (English PDF)

3.1 Reagents

3.1.1 Glacial acetic acid (C2H4O2).

3.1.2 Absolute ethanol (C2H6O).

3.1.3 Isooctane (C8H18).

3.1.4 95% ethanol.

3.1.5 Vegetable oil (olive oil, corn oil). It shall comply with the requirements of GB

5009.156.

3.1.6 Coconut oil (CAS number. 8001-31-8). chemically pure.

3.2 Reagent preparation

Food simulants. They shall be prepared in accordance with the regulations of GB

5009.156.

3.3 Materials

3.3.1 Absorbent cotton. white.

3.3.2 Grey scale for assessing staining. a grey scale for assessing staining that meets

the requirements of GB/T 251 (see Figure A.1 in Appendix A).

3.3.3 9-step chromatic transference scale. a 9-step chromatic transference scale that

meets the standard requirements of the American Association of Textile Chemists and

Colorists (AATCC) (see Figure A.2 in Appendix A).

3.3.4 Colorimetric tube with stopper. 50 mL, colorless, only full and half volume

colorless scale marks.

4.1 Electronic balance. The sensitivity is 0.1 g (maximum weighing capacity is >2.0

kg).

4.2 Analytical balance. The sensitivity is 0.1 mg.

4.3 Color assessment booth. It meets the requirements of GB/T 32387, and the light

source is standard illuminator D65.

5.1 Soak solution coloring

5.1.1 Soak solution preparation

The sample shall undergo a migration test in accordance with the corresponding product

standards, GB 31604.1, and GB 5009.156, the food simulants and migration test

conditions shall be selected in accordance with the requirements of the corresponding

product standards and GB 31604.1, and the area/volume ratio used for the migration

test shall be consistent with the area/volume ratio required by the result presentation.

The food simulant or chemical alternative solvent obtained from the migration test is

the soak solution. The migration test shall be carried out in at least 2 parallel tests.

5.1.2 Blank test

Process food simulants or chemical alternative solvents that are not in contact with the

sample to be tested according to 5.1.1, and the soak solution obtained is the blank soak

solution.

5.1.3 Coloring grade assessment

Experimenters shall have no color vision impairment. If laboratory personnel wear

corrective glasses, their lenses must have uniform spectral transmittance throughout the

visible spectrum. If an experimenter performs continuous colorimetry, the person shall

rest for a few minutes at certain intervals to ensure the quality of visual colorimetry.

Take colorimetric tubes with stoppers, add 50 mL of the soak solution that has been

cooled to room temperature and the blank soak solution respectively, and place them

on the colorimetric tube rack in the color assessment booth. Place the colorimetric tube

rack and grey scale or 9-step chromatic transference scale for assessing staining on the

same plane in the color assessment booth, and the experimenter shall observe it in the

horizontal direction. Visually evaluate the grey scale or 9-step chromatic transference

scale grade to which the color difference between the soaking solution and the blank

soaking solution belongs. The corresponding number is the coloring grade of the soak

solution.

5.2 Wipe decolorization

5.2.1 Sample preparation

The samples shall be pretreated in accordance with GB 5009.156, and 2 wipe

decolorization samples shall be prepared for each food simulant. Experimenters are

required to wear disposable nitrile gloves for the wipe test, and ensure that the nitrile

gloves worn do not discolor during the entire test process.

5.2.2 Preparation of food simulants for moistening absorbent cotton

The food simulant used for moistening absorbent cotton is selected according to the

total migration test provisions in the corresponding product standards, GB 31604.1, and

GB 5009.156.

5.2.3 Preparation of absorbent cotton

Take absorbent cotton, cut it into a size of 2 cmx2 cm in an area of uniform thickness,

with a mass of 0.25 g~0.30 g, and completely wet it with the food simulant selected in

5.2.2.

5.2.4 Experimenter's practice and confirmation of wiping force value

Take a plate or sheet of the same material as the sample to be tested, and place it on an

electronic balance (or other equivalent device that can display the wiping force value);

the experimenter presses the moistened absorbent cotton with the pulp of two fingers

(index finger and middle finger) to wipe back and forth 100 times in an area of about 4

cmx2 cm at a speed of about 1 time/s (wipe the absorbent cotton back and forth for one

round in the direction of the sample test, counting as 1 time). When wiping, apply force

evenly along the test surface, and observe the mass display on the electronic balance

throughout the process to ensure that the mass display during the entire wiping process

is stable within the range of 1.0 kg+/-0.2 kg.

5.2.5 Wipe decolorization test

Within an area of approximately 4 cmx2 cm on the food contact surface of the sample,

press the moistened absorbent cotton with the pulp of two fingers (index finger and

middle finger), and apply a wiping force that meets the requirements of 5.2.4 along the

sample surface to wipe back and forth 100 times at a speed of 1 time/s, to obtain

absorbent cotton after wiping. If an experimenter performs a continuous wipe

decolorization test, the person shall rest for a few minutes at certain intervals to ensure

the stability of the wiping force value.

5.2.6 Blank test

Use the sample of the same material that was confirmed not to be decolorized by wipe

decolorization test as the blank sample, and prepare blank absorbent cotton according

to 5.2.1~5.2.5.

5.2.7 Coloring grade assessment [Translator's note. here should be Wipe

decolorization grade assessment]

Place the wiping absorbent cotton, blank absorbent cotton, and grey scale or 9-step

chromatic transference scale for assessing staining on the same plane of the color

assessment booth. The incident light is at an angle of about 45° to the surface of the

absorbent cotton, and the observation direction is roughly perpendicular to the surface

of the absorbent cotton. Visually evaluate the grey scale or 9-step chromatic

transference scale grade to which the color difference between the absorbent cotton

after wiping and the blank absorbent cotton belongs. The corresponding number is the

wipe decolorization grade.