应用SDS-PAGE法评价乳基婴幼儿配方食品中有效蛋白质组分

Evaluation of Available Protein Components in Milk-based Infant Formula by SDS-PAGE

利用SDS-PAGE法评价乳基婴幼儿配方食品中的有效蛋白组分,优化了样品前处理方法,采用Bio-Rad Quantity One软件对电泳谱图进行数据分析,实现牛乳蛋白组分的定性和半定量测定。采用该法对我国市售婴幼儿配方食品中的牛乳蛋白有效成分进行了质量评价分析,发现0～12月龄婴儿配方食品基本符合GB 10765-2010中对乳清蛋白不得低于60%总蛋白的规定;0～6月龄Ⅰ段婴儿配方食品中的乳清蛋白含量最高,乳清蛋白/酪蛋白为1.57～2.12(61∶39～67∶33);6～12月龄的Ⅱ段较大婴儿配方食品中乳清蛋白相对Ⅰ段少,二者比例为1.06～1.55(52∶48～61∶39);而在12月龄以上的Ⅲ段幼儿配方食品中二者比例为0.65～0.71(40∶60～42∶58)。虽然Ⅰ段婴儿配方食品乳清蛋白/酪蛋白符合标准,但是在母乳中占主要成分的α-LA(α-乳白蛋白)在Ⅰ段婴儿配方食品中含量偏低(19.1%～24.1%),母乳中不存在的α-CN(α-酪蛋白)在Ⅰ段婴儿配方食品中却占11.9%～17.8%,另外还发现Ig G(免疫球蛋白G)在乳基婴幼儿配方食品中的含量偏低。

In this paper, the pre-treatment method and loading weight of SDS-PAGE which is suitable for carry- ing out structural analysis and evaluation of protein in infant formula is optimized, using Bio-Rad Quantity One soft- ware for data analysis of the electrophoresis spectrum, achieving qualitative and semi-quantitative analysis of milk pro- tein. Simultaneously, active ingredients of milk protein in the infant formula for infants up to 6 months, follow-on （ fol- low-up） formula for infants from 6 months to 12months and toddler formula for infants from 12 months on were ana- lyzed 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 re- quirement 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.