This standard supersedes "National Food Safety Standard - Determination of Impurities in Milk and Milk Products" (GB 5413.30-2010).
Compared with GB 5413.30-2010, this standard has the following main changes:
- technical requirements for filter plate of impurities are added;
- inspection procedures in Appendix A are simplified and the method of measuring the loss quantity of impurities is revised as measuring the residual quantity of impurities in the appendix;
- preparation of reference standard plate for impurities in Appendix B is revised as preparation methods of two types of standard plates for liquid milk and milk powder;
- the composition of impurities and size of particle are redetermined.
National Food Safety Standard
Determination of Impurities in Milk and Milk Products
食品安全國家標準
乳和乳制品雜質度的測定
1 Scope
This standard specifies the method for determining impurities in milk and milk products.
This standard is applicable to the determination of impurities in raw and fresh milk, pasteurized milk, sterilized milk, condensed milk and milk powder; it is not applicable to milk and milk products containing substances which affect filtering and containing insoluble colored matters.
2 Principle
Filter the samples of raw and fresh milk, liquid milk and milk powder renatured by water with impurity filter plate, and determine the impurity limit of samples by comparing the visible non-white residual impurities on impurity filter plate with the impurity reference standard plate.
3 Reagents and Materials
Unless otherwise specified, analytically-pure reagents and Grade III water (defined in GB/T 6682) are adopted for the purposes of this method.
3.1 Impurity filter plate: white cotton plate of 32mm in diameter, 135mg±15mg in mass and 0.8mm~1.0mm in thickness which shall meet the requirements of Appendix A. The impurity filter plate is inspected in accordance with Appendix A.
3.2 Impurity reference standard plate: see Appendix B for the fabrication method of the impurity reference standard plate.
4 Apparatuses
4.1 Balance: with sensibility of 0.1g.
4.2 Filtering equipment: impurity filter or suction flask, positive pressure or negative pressure mode may be adopted to realize rapid filtration (filtration time for each liter of water is 10s~15s). The effective filtering diameter after setting impurity filter plate is 28.6mm±0.1mm.
5 Analysis Procedures
5.1 Preparation of sample solution
5.1.1 Mix the liquid milk sample well, measure 500mL of it with measuring cylinder and determine immediately.
5.1.2 Accurately weigh 62.5g±0.1g of milk powder sample into a 1 000mL beaker, add into 500mL of 40℃±2℃ water, stir it sufficiently for dissolving and carry out determination immediately.
5.2 Determination
Place the impurity filter plate on filtering equipment, pour the prepared sample solution into the funnel of filtering equipment (shall not overflow the funnel) and then start filtering. Clean the beaker with water for many times and transfer the washing solution to funnel for filtering. Clean the funnel with washing bottle by many times for filtering, take out the impurity filter plate after filtering, and obtain the impurities in sample by comparing with the impurity standard plate.
6 Expression of Analysis Results
The result obtained by comparing the impurity filter plate after filtrating and the impurity reference standard plate is the impurities in sample.
When the impurity on the impurity filter plate is between two levels, the level with higher impurity shall prevail. If foreign matters like fiber appear, the impurity is judged as exceeding the maximum value.
7 Accuracy
Carry out determination twice for the same sample in accordance with the method described in this standard and these two results shall be consistent.
Contents
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Apparatuses
5 Analysis Procedures
6 Expression of Analysis Results
7 Accuracy
Appendix A Inspection of Impurity Filter Plate
Appendix B Preparation of Impurity Reference Standard Plate
