National Food Safety Standard

Transcription

1 Translated English of Chinese Standard: GB GB NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA GB National Food Safety Standard Determination of Impurities in Milk and Milk Products 食品安全国家标准乳和乳制品杂质度的测定 Issued on: March 26, 2010 Implemented on: June 1, 2010 Issued by: Ministry of Health of the People s Republic of China Page 1 of 9

2 Table of Contents Foreword Scope Normative references Principle Apparatus and equipment Analytical procedures Expression of analytical results Precision... 5 Annex A... 6 Annex B Page 2 of 9

3 Foreword This Standard replaces GB/T Milk and milk powder--determination of impurities. Annex A and Annex B of this Standard are normative. The previous edition replaced by this Standard is as follows: - GB/T Page 3 of 9

4 National Food Safety Standard Determination of Impurities in Milk and Milk Products 1 Scope This Standard specifies a method for determination of impurities in milk and milk products. This Standard is applicable to determination of impurities in pasteurized milk, sterilized milk, raw milk, condensed milk and milk powder. It is not applicable to those additives containing nondairy protein, starch ingredients, insoluble color substances and affecting filtration. 2 Normative references Documents referenced in this Standard are indispensable for application of this Standard. For dated references, only the dated edition is applicable to this Standard. For undated references, the latest edition (including all amendments) is applicable to this Standard. 3 Principle Impurity level is determined according to the quantity of visible colored impurities retained on the filter plate after the sample is filtered by a filter plate and washed. 4 Apparatus and equipment 4.1 Filter equipment: Impurity filter or 2000 ml ml filter flask equipped with the filter plate funnel. 4.2 Filter plate: 32 mm in diameter, 135 g/m 2 in mass per unit area, conforming to the requirements of Annex A, and 28.6 mm in diameter of discharge area during filtration. 4.3 Impurity standard plate. 4.4 See Annex B for preparation methods of impurity standard plates. 4.5 Balance: Sensibility is 0.1 g. 5 Analytical procedures Measure 500 ml of liquid milk sample. Weigh 62.5 g (accurate to 0.1 g) of milk powder sample. Use 8 times of water to fully mix and dissolve. Heat to 60 C. Weigh 125 g (accurate to 0.1 g) of condensed milk sample. Dissolve in 4 times of water. Heat to 60 C. Filter by the filter plate (a vacuum pump can be used to quicken the filtration). Wash the filter plate with water. Take down the filter plate. Put in a drying oven for drying. Then compare the impurities on the filter plate with those on the impurity standard plate to get the impurity level. When the content of impurities on the filter plate is between two levels, the impurity level with higher content of impurities is determined. Page 4 of 9

5 6 Expression of analytical results The impurity level on the filter plate that is obtained by comparing with the impurity standard is the impurity of this sample. 7 Precision The results of two repeated determinations of the same sample by the methods described in this Standard shall be consistent, otherwise another 2 determinations shall be repeated. Page 5 of 9

6 tube (outlet diameter is 3 mm). Use water to dilute to 1000 ml. A.2 Apparatus and equipment A.2.1 Balance: Sensibility is 0.1 mg. A.2.2 Dryer: Containing effective drying agent. A.2.3 Drying oven. A.2.4 Filter appratatus. A.2.5 Filter plate. A.2.6 Filter paper: 7 cm or 9 cm in diameter. A.3 Analytical procedures A.3.1 Put the filter paper (A.2.6) into a Buchner funnel. Wash with about 200 ml of water. Then put into the 100 C drying oven for drying to constant weight. A.3.2 Fully stir 60 ml of refined impurity mixture (A.1.4). Filter through the filter plate (A.2.5) installed on the filter apparatus. It is equivalent to 12 mg of impurities. Collect the filtrate with a clean conical flask. Transfer the filtrate into the beaker. Wash the conical flask twice with water. Add all washing liquid to the beaker. A.3.3 Filter the filtrate once again with the cleaned, dried and weighed filter paper (A.3.1) fixed in the Buchner funnel. Fully wash the beaker and the filter paper. Then put the filter paper into the 100 C drying oven for drying to constant weight. A.3.4 Inspect at least more than two filter plates. A.4 Evaluation Average weight of impurities passing through three or more filter plates is not more than 2.8 mg. Impurities shall not appear below the surface of the standard plates that are prepared and based on the refined impurity mixture. Page 7 of 9

7 Table B.1 Preparation Ratio of Impurity Standard Plates Number of standard plate Relative mass concentration of impurities Cow milk (mg/l); milk powder (mg/kg) 500 ml cow milk 62.5 g milk powder Absolute content of impurities (mg) Volume of measured mixed impurity solution (ml) END Page 9 of 9