Development Of Substitutes Of Whey Protein In Infant Formula

Undoubtly, human milk is the best natural food with advantages which is better than any other milk products. However, the feeding rate of human milk is low in our country and even in the world at present because of health conditions and work requirement. Bovine milk is believed to be the best choice for infant foumula ingredients owe to possessing plentiful nutrition and broad sources. Whey protein is often added into the forthcoming infant foumula to adjust the ratio of casein to whey protein, which is aiming to improve digestibility and nutrition value. However, almost no whey powder was produced in our country, which mainly depends on import. As a result, production of infant milk powder in our country has being restricted to the import of whey protein, which increased the the cost of infant formula and caused generously outflowing of foreign exchange. Meanwhile,β-lactoglobulin in whey protein is the chief factor causing hypersusceptibility of infant. So it is essential to develop a new kind of protein ingredient. Skim milk is a kind of easily developed protein ingredient for its abundant souce and simple preparation.Skim milk was hydrolyzed in the experiment. Digestibility was determined by in vitro mimic digestion, particle size distribution of protein coagulum in pH4 by laser diffraction, and the protein quanlity of hydrolysates by the international nutritive value evaluation method. Then the product most similar to human milk was chose. Meanwhile, antigenicity of them was determined by indirect competitive ELISA. The conclusions were obtained as follows:(1)The digestibility of hydrolysates was significantly improved by in vitro mimic digestion. The digestibility of 50 min hydrolysate was a little larger than that of human milk, and the digestibility of 60 min hydrolysate is approaching 100%. Thus, it is clear that hydrolization can efficiently raise the digestibility of protein.(2)The total content of amino acid which could be digested and absorbed in hydrolysates was larger than infant reference mode. But the contents of Leu and Trp were a little lower than that of infant reference mode. The results of nutritive value evaluation by essential amino acid chemical score, amino acid score, score of ratio coefficient of amino acid, essential amino acid index and biological value showed that the nutritive value of both 50 min and 60 min hydrolysates is higher than that of skim milk without hydrolysis, and it is approaching to human milk.(3)Particle size distribution of both 50 min and 60 min hydrolysates were similar to that of human milk. However, there were some differences in particle size distribution due to distinctions of natural proteins.(4)The antigenicities ofβ-lcatoglobulin, casein and bovine serum albumin were siganificantly decreased after hydrolyzed by pancreatin. The decreacing antigenicity rates in the 50 min hydrolysate were 55.69%, 87.11% and 85.69% respectively and 56.09%, 87.56% and 86.28% respectively in the 60 min hydrolysate.(5)The peptides distribution of hydrolysates analyzed by SDS-PAGE electrophoresis showed the molecular weight of peptides were almost below 20 kDa after hydrolyzing 50 min, but very few of them were less than 3.313 kDa.(6)The optimum conditions of hydrolysis was: concentration of substrate was 20%, E:S= 0.3%, temperature was 50℃, natural pH, hydrolysis time was 50 min or 60 min.A kind of protein ingredient which can substitute the whey protein in infant foumula was developed by this experiment. This milk protein ingredient is approaching to human milk in the aspects of digestibility, nutritive value and acid coagulating character. And the antigenicities ofβ-lcatoglobulin, casein and bovine serum albumin were redued significantly.The creation points of this test are as follows:(1)Particle size distribution of protein coagulum in hydrolysates was determined by laser diffraction method, which supplying a point of micro view to study the acid coagulating character of protein.(2)The digestibility,acid coagulating character and nuturative value of protein were all compared to those of human milk and chose the hydrolasate extremely similar to human milk.