Preparation Of Chicken Functional Peptides And Its Antioxidant Activity With Lentinan Polysaccharides

Chicken is rich in protein,rich in many amino acids,vitamins and minerals required by the human body.It has a well-balanced nutrition and is characterized by low fat,low cholesterol,and low calories.It has historically been listed as the"head of poultry meat,""The source of nutrition"and"the king of food supplements".This thesis studies the preparation process of chicken protein peptides.Its physical and chemical properties,molecular weight,free amino acid distribution and antioxidant activity were studied in order to provide a theoretical basis and technical support for the development of high value-added products such as nutritional bases,flavoring bases,and functional bases for chicken protein.The experimental results are as follows:Using chicken breast as raw material and the protein extraction rate as indexes,salt extraction method was adopted to conduct single-factor experiments on the ratio of material to liquid,temperature,salt concentration and extraction time.Using response surface experiments to further explore the optimum process conditions for brine leaching.The results showed that the process conditions for brine extraction were as follows:the ratio of solid to liquid was 1:6.52,the salt concentration was 1.2%,the extraction time was 2.5 h and the temperature was 10°C.The predicted value of the protein extraction rate was 65.0%at this time,and the verification experiment result was 64.7%.The difference between the predicted value and the actual value was not significant?p>0.05?.Acid protease was used to explore the enzymatic hydrolysis process of salt-soluble protein?SSP?.The results showed that the optimal conditions for enzymatic hydrolysis were 5 Ku/g enzyme?100,000 U/g?,pH 4.5,temperature 45°C,and extraction time 30min.The obtained peptide?EP1?had a short peptide content of 15.6 mg/mL,a degree of hydrolysis of 14.9%,a hydroxyl radical scavenging rate of 102.5%,and a total reducing power of 1.002.Optimizing the enzymolysis process of chicken myofibrillar protein after salt extraction.The effects of enzymolysis time,feed-to-liquid ratio,temperature°C,enzyme dosage,and pH on the content of short peptides,degree of hydrolysis,hydroxyl radical scavenging rate,and total reducing power were investigated.The experimental results showed that the optimal conditions for enzymatic hydrolysis were 8 h for the enzymolysis,8 Ku/g for enzyme?100,000 U/g?,a 1:2?g/mL?solid-liquid ratio,a pH of4.0,and an enzymatic temperature of 45°C.The short peptide content,degree of hydrolysis,hydroxyl radical scavenging rate,and total reducing power of the obtained enzymatically hydrolyzed peptide?EP2?were 27.3 mg/mL,25.88%,100.14%,and0.855,respectively.The anti-oxidation activity of salt-soluble protein?SSP?and enzymatic peptides?EP1 and EP2?obtained from the above optimal extraction scheme was determined.The results showed that SSP,EP1,and EP2 all had higher·OH,O^2-·,DPPH clearance.The activity and the total reducing power,the clearance rate and the total reducing power and concentration showed a certain dose effect.Among them,at the same concentration,the clearance rate and total reducing power of EP1 and EP2 were higher than that of SSP,indicating that the enzymolysis is beneficial to increase the antioxidant activity of the protein.The results of the thermal stability study of SSP showed that SSP is sensitive to heat and the protein denaturation was severe at a water bath temperature of 55°C for 3minutes.The results of the acid-base stability study of SSP showed that the pH value at6.0 may be the isoelectric point of SSP,and the solubility of the protein is better when it is far from pH 6.0.The acid-base stability study results of EP1 and EP2 showed that the pH value had no significant effect on the absorbance of EP in the range of pH 2.0-12.0?p<0.05?,indicating that EP has a larger processing range than SSP.The molecular weights of SSP and EP were determined by high-performance gel chromatography.The results showed that the components with an SSP molecular weight of>10000 accounted for 64.06%,and the components with 180⁵00 accounted for 19.05%;The composition of EP1 with a molecular weight of<1000 was 96.98%,and that of EP2 with a molecular weight of<1000 was 98.19%.The results of free amino acid composition analysis showed that the total amount of free amino acids of EP2 was 5.97 times that of EP1,while the content of short peptides was only 0.7 times that of EP1.And the content of essential amino acids,umami amino acids,branched-chain amino acids and hydrophobic amino acids contained in EP is extremely high,indicating that the high antioxidant activity of EP is the result of a combination of short peptides and amino acids.The infrared analysis results of the compounding process and product of enzymatic piptides?EP?and lentinan showed that The optimum process of lentinan and two enzymatic solutions?LNT+EP?is 100°C,polypeptide and polysaccharide mass ratio1:2,pH value 9.0,the antioxidant activity of LNT+EP was slightly weaker than that of control?G+EP?.Fourier transform infrared?FTIR?analysis of the product showed that there was no chemical bond change between the enzymatic hydrolysate and lentinan and glucose under experimental conditions,the increase in the antioxidant activity of the formulation is due to the synergistic effect between the sugar and the enzymatic peptides.