| With the improvement of people’s living standard,more and more people consume functional dairy products,and the market prospect is broad.China’s aging problem is becoming increasingly prominent.As the population of China accounts for a large number of people,the nutrition and health of middle-aged and elderly people has been widely concerned by the society.It is of great significance to develop functional dairy products.In recent years,bioactive peptides have attracted much attention from scientists because of their potential to promote health and assist in the treatment of diseases.However,most scholars focus on the research of single bioactive functional peptides.Therefore,there are many kinds of single bioactive peptides in the market,and there is a lack of peptides with multiple bioactive segments.In this paper,goat casein was used as the base material,hydrolysis degree was used as the response value to optimize the enzymatic hydrolysis parameters,the bioactivity of the enzymatic hydrolysis products was evaluated,and the bioactive peptides were identified by mass spectrometry.The obtained peptides were applied to the middle-aged and elderly formula milk powder in different addition ways,providing a new idea for the development of functional dairy products.The main conclusions of this study are as follows:(1)Study on optimal enzymolysis combination and technological parameters of goat casein.The results showed that the combination of alkaline protease and complex protease is the best enzymolysis method.The optimal process parameters of enzymolysis were determined by single factor test and response surface tests.As the conditions of substrate concentration was 7.0%,compound enzyme composition(1:1)addition amount was 7000U/g,enzymolysis temperature was 55℃,p H was 9 and enzymolysis time was 192 min.the degree of hydrolysis could reach(46.95±0.41)%.(2)Function evaluation of goat casein peptides(GCP).The results showed that the antioxidant activity,hypoglycemic activity and calcium holding capacity of GCP were higher than that of goat casein(GC),but had no significant effect on the hypolipidemic activity(P > 0.05).The simulated gastrointestinal digestion showed that GCP had good anti-gastric acid and anti-bile salt ability.After enzymolysis,the molecular weight of GCP mostly decreased to less than 10 k Da.Eight functional peptides were identified by mass spectrometry.They are SDIPNPIGSE,YQKFPQY,YQEPVLGPVR,RGPFPIL,TPVVVPPFLQPE,TQTPVVVPPF,TPVVVPPF and FPKYPVEPF.(3)Based on the dietary nutrition requirements of middle-aged and elderly people,the formula of protein peptides milk powder for middle-aged and elderly people was optimized.The quality evaluation showed that the product was light yellow in color,full in flavor,fine in condition,no caking,bad odor and impurities,and good punchability.The protein content of formula milk powder with peptides was better than the national standard,and other indexes were in line with the national standard.(4)Study on the technology of applying polypeptide to formula milk powder of middle-aged and elderly people.The study of peptides addition methods showed that dry method was superior to wet method in antioxidant activity and hypoglycemic activity.Only in terms of GCP activity preservation,GCP was more suitable for dry addition.Then,the color,particle size,odor and microstructure of the three milk powder were analyzed to explore the influence of peptides method on milk powder.The results showed that the response values of methyl and alcohols,aldehydes and ketones,sulfides and nitrogen and oxygen compounds changed after the addition of peptides.The chroma of DBMP is closer to that of MP;The particle size of WBMP was significantly smaller than that of DBMP(P <0.05).WBMP is more evenly mixed than DBMP,the particles are more complete and the dispersion is smaller.Therefore,both wet and dry methods of goat casein polypeptides formula milk powder production have their advantages and disadvantages.Enterprises can choose according to their own technological conditions. |
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