GB/T 5413.2-1997Milk powder and formula foods forinfant and young children--Determination of whey protein (English PDF)

Foreword

This Standard refers to the whey protein determination method of Morinaga, Japan.

This series of standards will replace GB 5413-85 from the date of implementation.

1 Scope

This Standard specifies determination method for the ratio of casein to whey protein content.

This Standard is applicable to the determination of the ratio of casein to whey protein content in milk powder and formula foods for infant and young children.

2 Method summary

After using SDS-PAGE, Laemmli method to sample, use an optical densitometer to determine each band of casein and whey protein separated in order of molecular weight. Calculate the ratio of casein to whey protein content.

3 Reagents

All reagents, if the specification is not specified, refer to analytically-pure reagents. All experimental water, if other requirements are not specified, refer to grade three water.

3.2 SDS sample buffer: 0.125mol/L Trsi-hydrochloric acid (pH 6.8), glycerin with volume fraction of 20%, 4% (m/V) SDS, 2-mercaptoethanol with volume fraction of 10%, bromophnol blue with mass fraction of 0.0025%.

3.3 Stain: Coomassie brilliant blue R-250 with mass fraction of 0.1%, methanol with volume fraction of 10%, acetic acid with volume fraction of 7.5%.

3.4 Decolorant: methanol with volume fraction of 10%, acetic acid with volume fraction of 7.5%.

3.5 Casein.

3.6 Refined whey protein (WPC).