GB 31638-2016National Food Safety Standard -- Casein (English PDF)

2.1 Casein

the product made from acid and enzymatic or membrane separation processes using milk and/or dairy product as raw materials; it is a mixture of alpha,

beta, kappa and gamma and its subtypes

2.2 Acid casein

the product made from degreasing, acidifying to make casein precipitate then through filtration, washing, drying and other processes using milk and/or dairy product as raw materials

2.3 Enzyme casein

the product made from degreasing, rennet to make casein precipitate then through filtration, washing, drying and other processes using milk and/or dairy product as raw materials

2.4 Membrane separation casein

the product made from degreasing, membrane separating casein then through concentration, sterilization, drying and other processes using milk and/or dairy product as raw materials

3.1 Raw material requirements

The raw material shall comply with the provisions of corresponding standards and/or regulations.

3.2 Sensory requirements

The sensory requirements shall comply with Table 1.

Annex A

Determination of casein

A.1 Principle

After the sample is sufficiently dissolved, the pH shall be adjusted to 4.6 with acetic acid and sodium acetate solution so as to precipitate casein. Filter to collect casein. The followings are same with the determination principle of

Method One or Method Two in GB 5009.5.

A.2 Reagents and materials

Unless otherwise stated, the reagents used in this method are of analytical grade and water is of grade three specified in GB/T 6682.

A.2.1 Sodium bicarbonate (NaHCO 3 ).

A.2.2 Sodium tripolyphosphate (Na 5 P3 O 10 ).

A.2.3 Glacial acetic acid (CH3 COOH): excellent grade pure.

A.2.4 Sodium acetate (CH3 COONa · 3H2 O).

A.2.5 Anhydrous sodium acetate (CH 3 COONa).

A.2.6 10% acetic acid solution: pipet 10 mL of glacial acetic acid (A.2.3) in a

100 mL volumetric flask, add water to set volume.

A.2.7 Sodium acetate solution (1 mol/L): weigh 41 g of anhydrous sodium acetate (A.2.5) or 68 g of sodium acetate (A.2.4), add water to dissolve and dilute to 500 mL.

A.2.8 Sodium acetate - acetic acid buffer solution: respectively pipet 1.0 mL of sodium acetate solution (A.2.7) and 1.0 mL of acetic acid solution (A.2.6) in a 100 mL volumetric flask, add water to set volume.

A.2.9 The rest are same with reagents and materials in GB 5009.5.

A.3 Instruments and equipment

Same with instruments and equipment in GB 5009.5.

A.4 Analysis steps

A.4.1 Sample processing