This standard specifies the method for determining the impurity content. This standard is applicable to the determination of the impurity content of liquid processed milk such as fresh milk, pasteurized milk, skimmed milk, and milk powder that does not contain non-milk protein or starch. GB/T 5413.30-1997 Determination of impurity content in milk and milk powder GB/T5413.30-1997 Standard download decompression password: www.bzxz.net

GB/T5413.30--1997
This standard modifies the text format of the method in Article 2.7 of GB5413-85, but does not change the content. This series of standards replaces GB5413-85 from the date of implementation. This standard is proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Dairy Standardization Center. The responsible drafting unit of this standard: National Dairy Quality Supervision and Inspection Center. Participating drafting units of this standard: Food Hygiene Supervision and Inspection Institute of the Ministry of Health, Zhejiang Light Industry Research Institute, Harbin Morinaga Dairy Co., Ltd., Nestle (China) Investment Services Co., Ltd. Main drafters of this standard: Wang Yun, Zhang Yujie, Huang Min, Wang Xiaoyu, Wang Xinxiang 347
1 Scope
National Standard of the People's Republic of China
Determination of impurities
Milk and milk powder
Milk and milk powder-Determination of impurities This standard specifies the method for the determination of impurities. GB/T 5413. 30—1997
Replaces GB5413-—85
This standard is applicable to the determination of impurities in liquid processed milk such as fresh milk, pasteurized milk, skimmed milk, and milk powder that does not contain non-milk protein and starch components.
2 Definitions
This standard adopts the following definitions.
Impurities
The amount of visible colored impurities that are insoluble in hot water at about 60°C and remain on the filter plate in 500mL of liquid milk sample or 62.5g of milk powder sample measured according to this method.
3 Instruments and equipment
Common laboratory instruments and:
3.1 Filtering equipment: positive pressure or negative pressure impurity filter or 2000~2500mL suction filter bottle (equipped with a porcelain filter funnel or special funnel that can hold a cotton filter plate).
3.2 Cotton filter plate: 32mm in diameter, 135g/m2 in density, in line with the requirements of Appendix A (Appendix of the standard), the diameter of the area through which milk passes during filtration is 28.6mm.
3.3 Impurity standard plate.
For the method of making the impurity standard plate, see Appendix B (Appendix of the standard). 3.4 Beaker: 500mL.
4 Kneading steps
4.7 Take 500mL of liquid milk sample and heat it to 60℃ (take 62.5g of milk powder sample, fully blend it with filtered water, heat it to 60℃ or directly blend it with 60C water). Filter on the cotton filter plate on the filter device, and rinse the milk attached to the filter plate with water. After drying the filter plate in an oven, compare it with the impurity standard plate in an indirect but uniform light to get the impurity content on the filter plate. When the impurity content on the filter plate is between two levels, it is judged as the level with a higher impurity content. 5 Expression of analysis results
The amount of impurities on the filter plate obtained by comparing with the impurity standard plate is the impurity of the sample. 6 Allowable difference
The results of two repeated measurements of the same sample according to the method described in this standard should be consistent, otherwise the measurement should be repeated twice. Approved by the State Administration of Technical Supervision on May 28, 1997 348
Implementation on September 1, 1998
A1 Materials
GB/T 5413.30-1997
Appendix A
(Appendix to the standard)
Testing of impurity filter plates
A1.1 Wetting agent: 1% solution. Use a wet mist or other suitable wetting agent. A1.2 Plant gum solution: Add 0.75g of carob bean gum or other suitable gum to 100mL of water and stir with a stirrer. Remove bubbles from the solution by vacuuming or heating. Boil, cool, and then add 2 mL of 40% formaldehyde solution (this will cause the insoluble plant debris to separate, making the supernatant clear for use). To facilitate separation in water without stirring, dissolve 0.75 g of carob bean gum in a few mL of ethanol in a 100 mL volumetric flask. Dilute to volume with water and mix thoroughly. Then continue as above. A1.3 Sucrose solution: Dissolve 750 g of sucrose in 750 mL of water. A1.4 Refined impurity mixture: 0.2 g/L dispersed phase. Prepare a mixture by drying ground cow dung, soil, and charcoal in a drying oven (100°C). Sieve each material separately and collect the components that pass through a 106 μm [diameter 203.2 mm (8 in)] sieve and do not pass through a 75 μm sieve as follows:
Place no more than 100 g of cow dung or soil and no more than 50 g of charcoal and sieve. Put another 75um sieve on the outside of the 106um sieve, cover and fix the receiving device. Shake the sieve cover by hand and sieve at a speed of 120 taps per minute. About 20g is used for one operation. The fragments that pass through the 106μm sieve continue to pass through the 75μm sieve for 5 minutes. Use the ingredients retained by the second sieving and mix them as much as possible in the following proportions:
Put 2g of the above mixture into a 100mL single-scale marked volumetric flask and moisten it with 5mL of wetting agent (A1.1). Add 46mL of vegetable gum solution, and then add the liquid level to the bottleneck with sucrose solution (A1.3). Add a few drops of ethanol, then add sucrose solution to the scale and mix thoroughly.
Pour the solution into a 250 mL beaker or bottle with a screw cap, allowing a small amount of air to enter, and stir with a small mechanical stirrer at a speed of 200-300 r/min until the impurities are evenly distributed under bright reflected light. Fix the blade of the stirrer so that fine particles do not accumulate in the vortex at the bottom of the beaker. While stirring, use a single-scale pipette (outlet diameter 3 mm) to transfer 10 mL (equivalent to approximately 200 mg of the impurity mixture) into a volumetric flask and make up to 1000 mL with water. A2 Equipment
A2.1 Balance: accurate to 0.0001 g.
A2.2 Desiccant: Contains effective desiccant.
A2.3 Drying oven: temperature controllable to 100°C. A2.4 Filtering device (see 6.6).
A2.5 Filter plate (see 6.5).
A2.6 Filter paper: 7cm or 9cm in diameter, high quality. A3 Steps
A3.1 Place the filter paper (A2.6) in a Buchner funnel, rinse with about 200ml of water, then place in a 100C oven to dry to constant weight, transfer to a covered desiccator, and weigh. 349
GB/T5413.30—1997
A3.2 Stir 60mL of the refined impurity mixture (A1.4) thoroughly, and filter through the filter plate (A2.5) installed on the filter device, which is equivalent to 12mg of impurities.
Collect the filtrate in a clean conical flask. Transfer the filter paper to a beaker, rinse the flask twice with water, and add all the washing liquid to the beaker.
A3.3 Pass the filtrate through the cleaned, dried, and good quality filter paper (A3.1) fixed in the Buchner funnel again. Rinse the beaker and filter paper thoroughly with water, then place the filter paper in a 100℃ oven and dry it to constant weight (A3.1). A3.4 Test at least two filter plates. A4 Evaluation
The average amount of impurities on each filter plate among three or more filter plates does not exceed 2.8 mg. A standard plate prepared based on a refined impurity mixture should not have impurities below the surface. Appendix B
(Standard Appendix)
Preparation of impurity standard plate
B1 Materials
Make coke powder, ash, cow dung, and charcoal pass through a certain sieve, then dry them in a 100℃ oven, and mix them according to the following proportions. Coke powder accounts for 40%, of which:
10% pass through a 20-mesh sieve but not a 40-mesh sieve; 30% pass through a 40-mesh sieve but not a 60-mesh sieve. Ash accounts for 30%,
can pass through a 40-mesh sieve.
Cow dung accounts for 20%, of which:
Those passing through the 20-mesh sieve but not the 40-mesh sieve account for 2%; those passing through the 40-mesh sieve but not the 60-mesh sieve account for 8%; and those passing through the 60-mesh sieve but not the 80-mesh sieve account for 10%. Charcoal accounts for 10%, of which:
Those passing through the 20-mesh sieve but not the 40-mesh sieve account for 4%; and those passing through the 40-mesh sieve but not the 60-mesh sieve account for 6%. B2 Steps
B2.1 Mix the various impurities that have been prepared (the total amount is preferably 50g), accurately weigh 1.000g from it, and pour it directly into a 500mL volumetric flask, add 2mL of distilled water and 23mL of filtered gum arabic solution with a volume fraction of 0.75%, and then add filtered sucrose solution with a mass fraction of 50% to the scale and mix well. The impurity concentration of this solution is 2mg/mLB2.2 Take 10 mL of impurity solution with a concentration of 2 mg/mL and dilute it to 100 mL with 500 g/L filtered sucrose solution. The impurity concentration of this solution is 0.2 mg/mL.
B2.3 Take 10 mL of impurity solution with a concentration of 0.2 mg/mL and dilute it to 100 mL with 500 g/L filtered sucrose solution. The impurity concentration of this solution is 0.02 mg/mL.
B2.4 Take 500 mL of milk or 62.5 g of milk powder as the sample volume and prepare each standard impurity plate according to Table B1. 350
Standard plate number
GB/T 5413.30—1997
Relative mass concentration of impurities, mol/L
500mL milk
62.5g milk powder
Absolute content of impuritieswww.bzxz.net
Quantity of mixed impurity liquid
6.25(0.02mg/mL)
18.75(0.02mg/mL)
3. 75(0. 2 mg/mL)
5. 00(0. 2 mg/mL)
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