Effect Of Starter On Protein Degradation And Peptide With Antioxidant Capacity Of Dry Fermented Sausage During Processing

Lactic acid bacterial,coagulase-negative staphylococci,yeasts,and molds are commonly used as starters in fermented sausages.During the processing of dry fermented sausages,microbial proteases and peptidases help release small molecule compounds such as peptides and amino acids.These small molecule compounds not only help fermented sausages to form unique flavors,but also have high antioxidant capacity.Protein and lipid oxidation are the main causes of quality degradation during the processing and storage of dry fermented sausages.In recent years,antioxidant peptides have attracted attention in the research of fermented meat products due to their excellent antioxidant activity,stable structure,and natural sources.However,there are few reports about the endogenous microbial hydrolysis of proteins to produce endogenous antioxidant peptides to delay the oxidation of proteins and lipids in fermented meat products.It has been reported that Lactobacillus plantarum CD101 and Staphylococcus simulans NJ201 have strong proteolytic activity and can inhibit the oxidation of fats and proteins in fermented sausages.Therefore,this study investigated the degradation of proteins and changes in the antioxidant capacity of peptides at various stages of processing by Lactobacillus plantarum CD101 and Staphylococcus simulans NJ201 through a fermented sausage system and in vitro simulation system.The specific research contents and conclusions are as follows:1.Effect of starter on protein degradation during the processing of dry fermented sausages.Lactobacillus plantarum CD 101 and Staphylococcus simulans NJ201 were inoculated into dry fermented sausages,and natural fermented sausages were used as a control group to determine the degradation of proteins during the processing of fermented sausages(0 d,1 d,4 d,9 d,and 23 d).The results showed that during the fermentation maturation process,the total number of lactic acid bacteria,staphylococci and total plate count all increased rapidly at first,then stabilized,and finally decreased slowly;the pH of the fermented sausage in the inoculation group decreased rapidly and was significantly lower than that in the control group(P<0.05);Non-protein nitrogen concentration increased during the processing,but not significantly different between the inoculation group and the control group(P>0.05);electrophoresis results showed that the starters could accelerate and aggravate degradation of sarcoplasmic protein and myofibrillar protein;According to the molecular weight distribution of the peptides,processing caused the content of peptides with molecular weights less than 3 kDa in the fermented sausage to increase continuously,and the inoculation group was higher than the control group.In addition,the free amino acid concentration of the fermented sausage in the inoculation group was significantly higher than that in the control group(P<0.05).Therefore,the use of the starters can effectively promote the protein degradation of the fermented sausage,accelerate the sausage ripening process,shorten the processing cycle,and improve the nutritional value and safety of the product.2.Effects of starter on antioxidant activity of peptide extract from dry fermented sausage during processing.Lactobacillus plantarum CD101 and Staphylococcus mimicus NJ201 were inoculated into fermented sausages,and natural fermented sausages were used as a control group.The crude peptides were subjected to ultrafiltration(MWCO 3 kDa)to determine the changes in the antioxidant activity during processing.The results showed the crude peptide concentration of the two groups increased during the processing,and the inoculation group was significantly higher than the control group(P<0.05),and the trend of small molecule peptide concentration was similar to that of the crude peptide;The free radical scavenging ability and reducing power of the crude peptide increased during processing.At the ripening stage,the DPPH free radical scavenging ability and FRAP value decreased,and the ability to chelate ferrous ions decreased during the processing;Except for the hydroxyl radical scavenging activity,the antioxidation changes of small molecule peptides are similar to that of crude peptides;the peptides of the inoculation group have stronger antioxidant capacity than the control group,and the small molecule peptides have stronger antioxidant capacity than the crude peptide.Therefore,the use of the starters can effectively promote the production of peptides,enhance the antioxidant capacity of peptides,especially small molecule peptides in fermented sausages,which help to extend the shelf life of the product.3.Effects of starter on degradation of muscle protein extract and the antioxidant capacity of products.Lactobacillus plantarum CD 101 and staphylococcus mimicus NJ201 were inoculated into pork sarcoplasmic and myofibrillar protein extracts.The uninoculated was used as a control group and incubated at 30℃ for 4 days.Degradation of the protein and changes in the antioxidant capacity of the peptides were observed.After isolation and purification,the peptides with strong antioxidant capacity were identified by LC-MS/MS.The results showed that the mixed starters could hydrolyze pork sarcoplasmic protein and myofibrillar protein;in the sarcoplasmic protein extract,the DPPH free radical scavenging activity,Fe2+chelation rate and ABTS free radical scavenging activity in inoculated group were significantly higher than the control group(P<0.05),but there was no significant difference in myofibrillar protein extracts(P>0.05);by RP-HPLC analysis,hydrophobic peptides were generated in the sarcoplasmic protein inoculated with starters,and the C2 and C5 showed high DPPH free radical scavenging activities,which were 66.60%and 60.50%respectively.By LC-MS/MS analysis,18 peptides were identified from the C2 and C5 components,mainly from phosphotriose isomerase,creatine kinase M type,and glyceraldehyde 3-phosphate dehydrogenase.Among them,hydrophobic amino acids account for a large proportion.Therefore,in-the absence of endogenous enzymes,the starter can hydrolyze sarcoplasmic proteins and myofibrillar proteins and produce peptides with antioxidant capacity.