Ding Fu-qiang, Qiu Kai, Zhong Qi-ding, Lv Xiao-ling, Li Jun-yan, Xiong Zheng-he
In this paper,the pre-treatment method and loading weight of SDS-PAGE which is suitable for carrying out structural analysis and evaluation of protein in infant formula is optimized,using Bio-Rad Quantity One software for data analysis of the electrophoresis spectrum,achieving qualitative and semi-quantitative analysis of milk protein.Simultaneously,active ingredients of milk protein in the infant formula for infants up to 6 months,follow-on(follow-up) formula for infants from 6 months to 12months and toddler formula for infants from 12 months on were analyzed for quality evaluation by this method,the results were found that all the infant formulas samples for infants 0~12 months conform to the requirement of GB 10765-2010 National food safety standard infant formula,whose requirement of least ratio of whey protein/ casein in infant formula is 1.5(60∶40).The infant formulas for infants up to 0~6 months had the most whey protein,whose ratio of whey protein/casein was between 1.7 and 2.12(61∶39~67∶33),the infant formula for infants 6~12 months had less whey,whose ratio was between 1.06 and 1.55(61∶39~52∶48),and the whey protein/casein ratio of infant formula for infant more than 12 months was between 0.65 and 0.71(40∶60~42∶58).Although,the infant formulas samples for infants 0~12 months conform to the requirement of GB 10765-2010 National food safety standard infant formula,the concentration of α-lactalbumin(the dominant protein in human milk) is relatively low in the formula(19.1%~24.1%),whereas α-casein,a protein not found in human milk,is between 11.9% and 17.8%,what's more,it was found that the concentration of Immunoglobulin(Ig) in infant formula was low.
