Milk and dairy products/infant food testing

This standard specifies the determination method of vitamin B: in infant and young child food and dairy products. This standard is applicable to the determination of vitamin B: in infant food and dairy products. 2 Normative References The documents referenced in this standard are essential for the application of this standard. For dated references, only the version with the date indicated applies to this standard. For undated references, the latest version (including all amendments) applies to this standard. The principle utilizes the specificity and sensitivity of Lactobacillus leichmannii to vitamin Bp to quantitatively determine the content of vitamin Bz in the sample. Supply all nutrients except vitamin Bg in the culture medium used for measurement, so that the transmittance generated by microbial growth corresponds to the content of vitamin B: in the standard curve working solution and unknown test solution. Draw a standard curve based on the transmittance of different concentrations of standard solutions relative to the concentration of standard substances at different concentration levels, and calculate the content of vitamin B: in the sample according to the standard curve. Unless otherwise specified, all reagents and materials used in this method are analytical pure, and the water is GB/T 6682 without identification result 4.1 Strain: Lactobacillus leichmannii (ATC& 7830. 4.2 Vitamin B: (Vitamin Bp or Cyanocobalamin) Standard substance: Molecular formula Ca; H. CoN, O, P, purity ≥ 99%. 4.3 Culture medium. 4.3.1 Lactobacillus agar culture medium: see Appendix A. 4.3.2 Lactobacillus broth culture medium: see Appendix A. 4.3.3 Culture medium for vitamin Bz determination: see Appendix A. Note: Some commercial synthetic media have good results, and commercial synthetic media should be prepared according to the label instructions. 4.4 9 g/L sodium chloride solution (physiological saline): Weigh 9.0 g of sodium chloride and dissolve it in 1000 mL of water. Divide it into stoppered test tubes, with 10 mL per tube. Sterilize at 121 ℃ for 15 minutes. 4.5 Ethanol solution: volume fraction is 25%. 4.6 Anhydrous disodium hydrogen phosphate (Na, HPO,). 4.7 Anhydrous sodium sulfite (NagS O,). 4.8 Citric acid (containing one crystal water) (CH: O. · H, O). 4.9 Preparation of standard solution. 4.9.1 Vitamin B: Stock solution (10 ug/mL): Accurately weigh vitamin B: standard (4.2), and dilute with ethanol solution (4.5) to a concentration of 10 ug/mL. 4.9.2 Vitamin Bp intermediate solution (100 ng/mL): Dilute 5.0 mL of vitamin Bz stock solution (4.9.1) to 500 mL with ethanol solution (4.5). 4.9.3 Vitamin Bp working solution (1 ng/mL): Dilute 5.0 mL of vitamin Bp intermediate solution (4.9.2) to 500 mL with ethanol solution (4.5)

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