| Egg is a kind of protein resources which is rich in a variety of nutrients,low price and easy to obtain.Its main components are egg yolk and egg white,egg white is the best raw material for the research and development of nutritional and health foods,which is rich in a variety of proteins.In addition,China is also the most country that consumes eggs,but at present,the consumption form is single,and the degree of deep processing of egg products is lower than developed countries.In recent years,with the improvement of people's living standards and the change of dietary structure,more and more people suffer from obesity,and a series of chronic diseases caused by obesity seriously threaten to people's physical and mental health.Therefore,in this study,egg white protein was used as raw material to prepare bioactive peptides with weight loss effect by protease hydrolysis,and the separation and purification of active peptides and the evaluation of weight loss efficacy were carried out.The main results are shown as follows:(1)Five proteases such as pepsin,alkaline protease,neutral protease,papain and trypsin were used to hydrolyze chicken egg white to prepare chicken egg white olytic lysate.The results showed that the enzyme hydrolysates of alkaline protease,neutral protease,papain and trypsin had higher inhibitory effect on lipase than that of nonhydrolyzed chicken egg white(13.60 ± 0.43%),and the inhibition rate of alkaline protease hydrolysate on trypsin(49.77 ± 0.10%)was significantly higher than that of other proteases(P<0.05).Therefore,the best hydrolase for hydrolyzing chicken egg white is the alkaline protease.(2)The effects of substrate concentration,hydrolysis time,temperature and enzyme dosage on the inhibition rate of lipase from egg white protease hydrolysate were studied by single factor test and response surface test,and a multiple regression model was established.The technological parameters of lipase inhibition rate of egg white protease hydrolysate were optimized.The results showed that the inhibitory effect of egg white protein on lipase was the highest when the substrate protein concentration was 80 g/L,Enzyme concentration 2240 U/g,at 55? for 4 h.the content of hydrolysate polypeptide was 101.29 mg/mL,The inhibition rate of lipase was the highest(56.06 ± 2.64%).The inhibition rate of ?-amylase was 25.16 ± 1.65%.(3)To study the effect of simulated gastrointestinal fluid on the inhibition rate of pancreatic lipase from alkaline protease hydrolysate.The alkaline protease hydrolysate was prepared under the optimum conditions of enzyme hydrolysis.Compared with before simulating gastric juice,the inhibition rate of chicken protease hydrolysate to pancreatic lipase per milligram peptide was 0.53% after digestion with simulated gastric juice,and there was no significant difference(P>0.05).After digestion of simulated intestinal fluid,the inhibition rate of pancreatic lipase per milligram peptide decreased to 0.46%,Compared with before simulating intestinal fluid,the difference was significant(P<0.05),but the overall inhibition rate was still high,which could achieve the expected effect.(4)Preliminary study on the separation and purification of macroporous adsorption resin and gel chromatography of egg white protease,the results showed that there was no significant difference between the eluates(P>0.05),but the macroporous adsorption resin was eluted with distilled water.The components had the highest inhibitory effect on lipase,the inhibition rate was 8.59 ± 3.41%,and the polypeptide content was 156.76 mg/mL.The eluted fraction of distilled water was further separated by gel chromatography,a total of 5 peaks were generated.The peak inhibition rate of pancreatic lipase per mg of egg albumin was 2.39 ± 0.04%,which was 4.35 times that before separation,and there was a significant difference with other peaks(P<0.05).(5)C57BL/6J that were 7-week-old male mice,were randomly divided into 6 models: normal control group,obese model control group,positive drug control group,egg white protein source diet peptide low,high dose group and weight loss peptide compound group.The normal control group was fed with basal diet,and the other 5 groups were fed with high fat diet.After successful modeling of nutritional obese mice,6 groups of mice were administered with normal saline and normal saline and orlistat 60 mg/kg·d,egg white protein-derived active peptide 400 mg/kg·d,800 mg/kg·d and compound weight-loss peptide 400 mg/kg·d through this way that were infused to stomach of mice,were given continuously for 28 days,and then the neck was severed and killed.The effect of egg white protein active peptide on weight loss was analyzed and evaluated.The normal control group was fed with basic diet and the other five groups were fed with high fat diet.The results showed that this way had no significant effect on food intake of mice(P>0.05).But high fat diet induced the increase of Lee's index,abdominal and subcutaneous fat coefficient,liver index and serum TC,TG,HDL-C,LDL-C.The Lee's index,abdominal fat coefficient and liver index of mice were inhibited to a certain extent by stomach of egg white protein active peptide,and the serum TC,TG,HDL-C,LDL-C level of mice was decreased.Therefore,Egg white protein weight loss peptide can inhibit the growth of obesity index,and has a certain weight loss and lipid reduction effect.The high dose group of egg white protease hydrolysate has a relatively large degree of inhibition on each index.The Lee's index,abdominal fat coefficient and liver index of mice were inhibited to a certain extent by stomach of egg white protein active peptide,and the serum TC,TG,HDL-C and LDL-C,level of mice was decreased.Therefore,Egg white protein weight loss peptide can inhibit the growth of obesity index,and has a certain weight loss and lipid reduction effect.The high dose group of egg white protease hydrolysate has a relatively large degree of inhibition on each index. |
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