Study Of In Vitro Evaluation Of Protein Quality In Infant Formula

International general nutrition value evaluation methods adopted, contents of protein and amino acid of milk-based and soybean-based infant formula home and abroad menstruated and analyzed,contents of breast milk published in2007treated as reference protein and amino acid requirement pattern of different stages of infants treated as evaluating standard,overall assessment of protein quality in infant formula was done by amino acid score,chemical score.essential amino acid index,biological value,nutrition index,ratio coefficient of amino acid,score of ratio coefficient and protein digestibility corrected amino acid sore(PDCAAS). The results show that the nutrient value of infant formula for infants0-6months,6-12months,12-24months were very high,especially infant formula for infants0-6months,the amino acid contents of which were close to those of human milk and could satisfy the amino acid requirements of infants.With the other same conditions,five different formula under three different sterilizing conditions adopted, meanwhile,the protein and amino acid of homemade samples were menstruated and analyzed, and its chemical score,essential amino acid index, biological value and nutrition index were evaluated. The results showed that lysine responsed obviously in different processing conditions,which proved that it could be recognized as an index for nutrition damage to infant formula. Chemical score was higher under the sterilizing condition,138℃,5s,than other conditions. Therefore, high temperature and instantaneous time sterilization was benefit for keeping nutrition. Because the contents of protein were different,the nutrition index would be very close.A method of determination of available lysine in infant formula powder with2,4,6-trinitrobenzene sulfonic acid(TNBS) was established.in which ether usage,hydrolysis time and incubation time with TNBS were studied. Good linearity was obtained in the range of0.02mg/mL-0.12mg/mL(r=0.9993),the determination limit was3.72μg/mL, and quantitative limit was10.23μg/mL and the sample spiked recoveries were in range of86%-115%with the reproducibility RSD of1.55%-5.57%. The TNBS (2,4,6-trinitrobenzene sulfonic acid) method determined available lysine content in milk-based formula compared to that in breast milk (69mg/g protein). Research found that available lysine in stage Ⅰ, stage Ⅱ, stage Ⅲ formula were56-88mg/g protein,68-96mg/g protein,61-77mg/g protein respectively.In addition total lysine content in domestic brands of infant formula was higher than that, except someone, while available lysine content was lower than that. Total lysine content in foreign brands of formula was more or less to that in domestic formula while available lysine content was higher than that. Available lysine content in infant formula stage II,was almost higher than that which in infant formula stage Ⅲ was basically equal with that.Therefore available lysine content in milk-based formula should be strengthened,which should be provided in standards.