GB 1987-2007Food additive -- Citric acid (English PDF)

6.6.2.5 Hydrogen peroxide solution (3%). pipette 10mL of 30% hydrogen peroxide

and dilute with water to 100mL.

6.6.2.6 Sodium hydroxide solution (300g/L). weigh 30g of sodium hydroxides, dissolve with water and dilute with water to 100mL.

6.6.2.7 Starch indicating solution (10g/L). prepare according to GB/T 603.

6.6.2.8 Ferric chloride.

6.6.2.9 Cobalt chloride.

6.6.2.10 Yellow stock solution

Weigh 46g of ferric trichloride (6.6.2.8); dissolve in about 900mL of hydrochloric acid solution (6.6.2.1); dilute with such hydrochloric acid solution to 1000mL. In calibration, adjust the yellow stock solution with hydrochloric acid solution (6.6.2.1), so as to make that 1mL of such yellow stock solution contains 46mg of FeCl3·6H2O. Solution shall be protected from light and calibrated for immediate use.

Calibration. pipette 10mL of the newly-prepared ferric trichloride solution; add 15mL of water, 4g of potassium iodide (6.6.2.2), and 5mL of hydrochloric acid solution (6.6.2.1);

plug the bottle cap immediately and stand still from light for 15min; add 100mL of water; titrate the iodine precipitated out with standard volumetric solution of sodium thiosulfate (6.6.2.4) until to pale yellow; add 0.5mL of starch indicating solution (6.6.2.7); titrate continuously until to endpoint.

Note. 1mL of 0.1mol/L standard volumetric solution of sodium thiosulfate is equivalent to 27.03mg of FeCl3-6H2O.

6.6.2.11 Red stock solution

Weigh 60g of cobalt chloride (6.6.2.9); dissolve in about 900mL of hydrochloric acid solution (6.6.2.1); dilute with such hydrochloric acid solution to 1000mL. In calibration, adjust the red stock solution with hydrochloric acid solution (6.6.2.1), so as to make that 1mL of such red stock solution contains 59.5mg of CoCl2·6H2O. Solution shall be protected from light and calibrated for immediate use.

Calibration. pipette 5.0mL of the newly-prepared cobalt chloride solution; add 5mL of hydrogen peroxide solution (6.6.2.5) and 10mL of sodium hydroxide solution (6.6.2.6);

boil slowly for 10min and cool down. Add 2g of potassium iodide (6.6.2.2) additionally, and 60mL of sulfuric acid solution (6.6.2.3); plug the bottle cap immediately. Shake gently to dissolve precipitates; titrate the iodine precipitated out with standard volumetric solution of sodium thiosulfate (6.6.2.4) until to be pale yellow; add 0.5mL of starch indicating solution (6.6.2.7); titrate continuously until the solution appears in pink.

Take two 50mL colorimetric tubes with stopper; add 1 mL of barium chloride solution (6.9.2.2) respectively; add 1mL of sulfate standard solution; shake and stand still for 1min. Pipette 15mL of sample solution into one of the colorimetric tube; pipette 10mL of sulfate standard solution and 5 mL of water (standard tube) into the other colorimetric tube; then respectively add 1 mL of hydrochloric acid solution (6.9.2.1) and 0.5 mL of acetic acid solution (6.9.2.4); shake them up; after 5min, the milk scale of sample tube shall not be darker than that of standard tube.

For anhydrous citric acid. It shall use sulfate standard solution II (6.9.2.6). for citric acid monohydrate, it shall use sulfate standard solution III (6.9.2.7).

6.10 Oxalate

6.10.1 Apparatuses

6.10.1.1 Colorimetric tube with stopper. 25mL.

6.10.1.2 Test tube. 15mm×180mm.

6.10.2 Reagents and solutions

6.10.2.1 Hydrochloric acid.

6.10.2.2 Phenylhydrazine hydrochloride solution (10g/L). prepare according to GB/T

603.

6.10.2.3 Potassium ferricyanide solution (50g/L). weigh 5g of potassium

ferrocyanide; dissolve it with water to 100mL.

6.10.2.4 Zinc granule.

6.10.2.5 Oxalate standard solution I (0.25 g/L). weigh 0.175 g of oxalate

(C2H2O4·2H2O); dissolve it with water to 500 mL.

6.10.2.6 Oxalate standard solution II (0.01g/L). pipette 4 mL of oxalate standard

solution I (6.10.2.5); dilute with water to 100 mL.

6.10.3 Procedures

Weigh 0.4 g of sample (accurate to 0.01g) to a test tube; add 4ml of water, 3ml of hydrochloric acid, and 1g of zinc granule; boil for 1min and place for 2min. Transfer it to a test tube that has contained 0.25mL of phenylhydrazine hydrochloride solution (6.10.2.2); heat to boil; rapidly cool down; pour it to a 25 mL colorimetric tube with stopper; add 0.25mL of isochoric hydrochloric acid and 0.25mL of potassium ferricyanide solution (6.10.2.3). Shake it and place for 30min. Make a visual colorimetric determination with standard tube prepared by the following methods; the pink seen from the sample tube shall not be darker than that seen from the standard tube.

requirements of this standard.

7.4.2 Ex-factory inspection items. content, light transmittance, water content, readily

carbonizable substance, chloride, sulfate, oxalate, calcium salt, ferrum, and water insoluble.

7.5 Type inspection

7.5.1 Type inspection items. besides the ex-factory inspection items, the type

inspection items shall also cover identification test, sulfuric ash, arsenic salt, and heavy metal.

7.5.2 Generally, type inspection is carried out every three months. Howe...