Antioxidant Activity Of Lactobacillus Plantarum And Formation And Stability Of Antioxidant Peptides In Fermented Sausage

Oxidative rancidity is one of the main quality problems in the processing and storage of fermented sausage,which will cause the deterioration of color,flavor and nutrition.With the gradual elimination of synthetic antioxidants,natural substances with antioxidant activity have been widely used in fermented sausages.As a common starter in fermented meat products,some lactic acid bacteria have good antioxidant activity in vitro,which provides a new way to inhibit the excessive oxidation of fermented sausages.In addition,LAB have protease activity,which can promote the production of bioactive peptides(such as antioxidant peptides)in sausage.However,the activity of bioactive peptides is unstable and vulnerable to environmental factors.Lactobacillus plantarum CD101,isolated from traditional Chinese sausage and inoculated into fermented sausage,was found to be effective in inhibiting the oxidation of sausage.But its action mechanism is unclear.Based on this,this study aimed to determine the antioxidant activity of Lactobacillus plantarum CD101,formation and stability of antioxidant peptides in inoculated fermented sausages.The detailed contents and conclusions are shown as follows:1.Antioxidant Activities of Lactobacillus plantarum CD101The fermented supernatants,intact cells and cell-free extracts were extracted from Lactobacillus plantarum CD 101.Antioxidant activity were investigated using 1,1diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging activity,Fe2+-chelation activity,hydroxyl radical(·OH)scavenging activity,superoxide anion(O2-·)scavenging activity,reducing ability,superoxide dismutase(SOD)activity,glutathione peroxidase(GSH-Px),catalase(CAT)as indicators.Different components possessed different antioxidant capacity.The DPPH· scavenging activity and reducing ability of the fermentation supernatant were the highest(P<0.05).Intact cell had the highest activity of Fe2+-chelation,O2-·scavenging and ·OH scavenging,81.42%,93.32%and 18.60%,respectively.Moreover,activities of SOD?GSH-Px and CAT were found in the fermentation supernatant and intact cells.L.plantarum CD101 had good antioxidant activity and can be used as an antioxidant in fermented sausage production,providing a new way for sausage antioxidant.2.Effect of Lactobacillus plantarum on antioxidant peptide formation of fermented sausageThis study investigated the effect of Lactobacillus plantarum CD 101 on the protein degradation and antioxidant peptide formation of fermented sausage.The non-inoculated group served as a control.The starter culture can effectively decrease the pH value and promote protein degradation,with increasing band strength at 12-17 kDa.Compared with those in the control group,the concentration of the peptides were increased significantly(P<0.05).And DPPH radical scavenging activity increased significantly(P<0.05),Fe2+-chelation rate decreased,ABTS radical and hydroxyl radical scavenging rate did not change significantly(P>0.05).A total of 44 peptides were identified by LC-MS/MS.The peptides in the control group were mainly derived from enzymes,whereas those in the inoculated group were produced by actin and myosin.The masses of the peptides were less than 3 kDa,and their amino acid sequences were between 5 and 27 amino acids in length.These results demonstrated that L.plantarum CD 101 effectively promote the protein degradation,contribute to peptide formation,improve the antioxidant activity,and ensure the safety of sausages.3.Antioxidant stability of peptides extracted from fermented sausagesThe effect of temperature,pH,food materials(NaCl,glucose,sucrose,NaNO2),metal ions,and simulated gastrointestinal digestion on DPPH radical scavenging activity,Fe2+-chelation ability and ABTS radical scavenging activity were investigated.The results showed that the radical scavenging rate decreased significantly(P<0.05)in high temperature,acid and alkaline environment,while the Fe2+-chelation rate increased with a low scope;NaCl and glucose,sucrose were beneficial to improve the radical scavenging activity,while inhibited the Fe2+-chelation activity;NaNO2 had little effect on the antioxidant peptide activity when the addition amount was within the permitted range of national standard;compared with K+,antioxidant peptides were more sensitive to Cu2+;the DPPH radical scavenging activity was completely lost after the simulated gastrointestinal digestion,but the Fe2+-chelation activity was increased to 1.4 times that of undigested,ABTS radical scavenging rate was stable at about 40%,with the free amino acid content gradually increased.