GB 5413.30-2016National food safety standard - Determination of Impurities in Milk and Milk Products (English PDF)

Foreword

This Standard replaces GB 5413.30-2010, National Food Safety Standard –

Determination of Impurities in Milk and Milk Products.

Compared with GB 5413.30-2010, the major changes of this Standard are as follows.

-- the technical requirements for impurities filter plate are added;

-- the testing procedures in Annex A are simplified and the measurement of

impurities loss is modified into the measurement of impurities residuals in the

Annex;

-- the preparation of impurities reference standard plate is modified into the methods

for the preparation of two standard plates for liquid milk and milk powder;

-- the constituents and particle size of impurities are redefined.

National Food Safety Standard -

Determination of Impurities in Milk and Milk Products

1 Application Scope

This Standard specifies the method for the determination of impurities in milk and milk

products.

This Standard applies to the determination of impurities in fresh and raw milk,

pasteurized milk, sterilized milk, condensed milk and milk powder; it does not apply to

the determination of impurities in milk and milk products added with substances which

decrease the efficiency of filter and insoluble coloured matters.

2 Principle

The specimen of fresh and raw milk, liquid milk, water reconstituted milk powder is

filtered through impurities filter plate; the limit of impurities in the specimen is

determined by comparing the visible non-white impurities remaining on the impurities

filter plate with the impurities reference standard plate.

3 Reagents and Materials

Unless stated otherwise, the reagents used in this Method are analytically pure and

the water is grade-3 water as specified in GB/T 6682.

4 Apparatus

5 Analytical Procedures

500 mL immediately before determination.

6 Expression of Analytical Results

The result obtained by comparing the impurities filter plate after filtering and the

impurities reference standard plate is the degree of impurities in the specimen.

7 Accuracy

For two tests repeated on the same specimen in accordance with the method specified

in this Standard, the results shall be consistent.

Annex A

(Normative)

Testing of Impurities Filter Plate

A.1 Reagents and Materials

A.1.1 Reagents

A.1.2.3 Carob bean gum. biochemical reagent.

A.1.2.4 Sucrose.

A.1.2 Preparation of reagents

A.1.2.1 Methyl alcohol solution (40%). measure 40 mL of methyl alcohol to pour into

a 100-mL volumetric flask, add water dropwise to 100 mL, and filter as standby.

A.1.3 Material

Impurities. use dirt on the floor to dry in a constant temperature drying oven (100°C ±

1°C), use a standard screen to collect dirt constituents of particle size 75 µm ~ 106 µm,

and dry to constant weight.

A.2 Apparatus

A.2.1 Balance. sensitivities 0.1 g and 0.1 mg.

A.2.2 Standard screen.

A.2.3 Desiccator. containing effective desiccant.

A.2.4 Constant temperature drying oven. accuracy ± 1°C.

A.2.5 Filter equipment. as in 4.2.

A.3 Testing procedures

A.4 Evaluation

A.4.1 M = N2 - N1, M shall be >= 10 mg. And use a sharp razor blade to cut off the

surface layer of the impurities filter plate and examine the remaining part where no

impurity shall appear.

A.4.2 Test 10 pieces per 1 000 pieces and count as 1 000 pieces if less than 1 000

pieces.

Annex B

(Normative)

Preparation of Impurities Reference Standard Plate

B.1 Reagents and materials

B.1.1 Reagents

B.1.1.1 Arabic gum. biochemical reagent.

B.1.2 Preparation of reagents

B.1.2.1 Arabic gum solution (0.75%). weigh 1.875 g of Arabic gum to pour into a 100-

mL beaker, add 20 mL of water and heat to dissolve, and cool down. Use water to

transfer to a 250-mL volumetric flask and add dropwise to the scale, and filter.

B.1.2.2 Sucrose solution (50%). weigh 1 000 g of sucrose to place into a 1 000-

beaker, add 500 mL of water to dissolve, use water to transfer to a 2 000-mL volumetric

flask and add dropwise to the scale, and filter.

B.1.3 Preparation of materials

B.1.3.1 Cow dung

B.2 Apparatus

B.2.1 Balance. sensitivities 0.1 g and 0.1 mg.

B.2.2 Standard screen.

B.2.3 Filter equipment. as in 4.2.

B.3 Procedures for preparing liquid milk reference standard impurities plate

B.3.1 Preparation of liquid milk impurities reference standard solution

B.3.1.1 Weigh accurately 500.0 mg of cow dung to place into three 100-mL beakers,

namely A, B and C. Add 2 mL of water, add 23 mL of Arabic gum solution, use sucrose

solution to transfer to a 500-mL volumetric flask after mixing up and add dropwise to

the scale, fully mix up until the impurities distributes uniformly, and obtain the cow dung

impurities reference standard solutions of concentration 1.0 mg/mL, namely a0, b0 and

c0.

B.3.2 Preparation of liquid milk reference standard impurities plate

B.3.2.1 Measure 100 mL of sucrose solution, filter on the filter equipment where the

impurities filter plate is mounted, use 100 mL of water of 40°C ± 2°C to wash the filter

plate for several times and dry by airing. Then the impurities plate is the impurities

reference standard plate A1 for the impurities' relative content in the liquid milk 0 mg/kg.

B.3.2.4 Absorb accurately 18.75 mL of the cow dung impurities reference standard

working solution a2 to pour into a 100-mL volumetric flask, use sucrose solution to

dilute and add dropwise to the scale, filter on the filter equipment where the impurities

filter plate is mounted after mixing up, use water to wash the volumetric flask, and filter

the washings together. Then use 100 mL of water of 40°C ± 2°C to wash the filter plate

for several times, and dry by airing. The impurities plate is the impurities reference

standard plate A4 for the impurities' relative content in liquid milk 6 mg/8 L.

B.3.3 Use 500 mL of liquid milk as the sampling quantity and see Figure B.1 for the

liquid milk impurities reference standard plates prepared in accordance with Table B.1

– Correlation of Liquid Milk Impurities Reference Standard Plates.

Table B.1 – Correlation of Liquid Milk Impurities Reference Standard Plates

Reference standard plate number A1 A2 A3 A4

Impurities solution

concentration/(mg/mL) 0 0.02 0.02 0.02

Impurities solution volume taken/mL 0 6.25 12.5 18.75

Impurities absolute content/(mg/500

mL) 0 0.125 0.250 0.375

Impurities relative content/(mg/8 L) 0 2 4 6

Figure B.1 – Liquid Milk Impurities Reference Standard Plate

B.4 Procedures for preparing milk powder impurities reference standard plates

B.4.1 Preparation of milk powder impurities reference standard solution

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