The Analysis Of Ingredients In Different Heat-Treated Milk Whey Protein And Assessment Of Nutritional Value

Newborn infant is the initial stage of life, is the most rapid phase of growth and development. They require a lot of nutrition, especially the high demand of protein. Lack of protein is able to affect the development of infant brain and the health for a lifetime. But the digestion and absorption in cradle are not prefect, and this is contradict with high nutrition they need, both of digestion and nutrition prone to disturbance. Therefore the food that suitable for infancy is very important for growth.According to the characteristics of the infant, undoubtedly, human milk is the natural food with advantages which is better than any other milk products. However, the feeding rate of human milk is low in our country at present because of health conditions and work requirement. Bovine milk is believed to be the best choice for infant formula ingredients owe to possessing plentiful nutrition and broad sources. Whey protein is often added into the forthcoming infant formula to adjust the ratio of casein to whey protein. Whey protein has a significant effect on the growth and development of the baby. Whey protein can provide a lot of High quality protein for baby growth which can be digested and absorbed easily to baby and have influence to the baby’s immune function. However, many heat treatments are in the processing of desalinated whey powder, such as pasteurization and spray drying. These heat treatments will lead to denaturation of desalinated whey powder, and reduce both of the nutritional value and digestibility.In this study the milk as raw material, remove the casein precipitated by acid cogulation and get the whey protein. Determine the α-lactalbumin and β-lactoglobulin denaturation rate in different heating temperature and time by using high performance liquid chromatographic determination of whey protein, and get almost completely denatured whey protein. The experimental results show that heating is positively correlated to the milk whey protein denaturation rate,and P-lactoglobulin is not reversible reaction of thermal stability is lower than a-lactalbumin.95℃heating20min, whey protein denaturation is92.27%.Determination of the main ingredients (protein, carbohydrates and amino acids) of the acid whey powder (unheated whey), the pasteurized whey powder (85℃,15s whey), the denatured whey powder (95℃,20min whey) and the desalinated whey powder (commercially available), and then, respectively, using high performance liquid chromatography for the determination of soluble protein, the fluorescence method for the determination of available lysine content, DNTB colorimetric determination of free sulfhydryl content. The results show that the desalination of whey soluble proteins chemically modified, resulting in the desalination of whey powder composition change. Pasteurizeds affection to whey protein denaturation is smaller; the essential amino acid content of the desalination of whey is lower than the acid whey powder, lysine loss rate25.12%, higher than the bar to kill whey and modified whey powder.Free sulfhydryl content lower than the denatured whey powder, increase rate of16.65%.Through the above four kinds of whey powder in vitro digestibility experiments, the lowest digestibility of the desalination of whey powder, is65.25percent, and the difference was not significant between digestibility of pasteurization and acid whey powder.Digestion by animal experiments, compared with the acid whey powder, were measured in the denatured whey powder, and desalination whey, digestibility, blood urea nitrogen content and intestinal amino acid content. The experimental results show that the desalination of whey protein digestibility of67.87%, obtained with the simulation experiments in vitro digestibility close, blood urea nitrogen were significantly lower than the acid whey powder (P<0.05), no significant denaturation of whey powder differences in amino acid content1h small intestine is slightly lower than the acid whey powder.After several rounds of heat treatment in the production process, the desalination of whey powder will lead to reduce the nutritional value and the negative impact of the baby’s digestion and absorption. Therefore, the development of a desalination of whey powder substitute for, or developing a set does not lead to the desalination of whey protein denaturation, whey powder production process is the most important issue of infant formula.