Effects Of Different Protease-Producing Lactic Acid Bacteria On The Protein Of Air-Dried Beef

Air-dried beef is a traditional characteristic fermented meat product of Xinjiang Kazakhs,and it is popular because of its unique aroma and texture.The texture of meat products is basically determined by the condition of the protein.The strong volume shrinkage,texture changes and flavor formation during the meat production process are closely related to the changes in functional properties caused by the conformational changes of the protein.This study took air-dried beef as the research object,and was fermented with protease-producing lactic acid bacteria.It explored the changing trend of beef protein during fermentation from the three aspects of protein degradation,oxidation and structural characteristics,aiming to gain a deeper understanding of the change mechanism of air-dried beef quality and provide a theoretical basis for ensuring the safe production of air-dried beef.The results of the study are as follows:1.Effects of protease-producing lactic acid bacteria on the formation of physical and chemical properties and safety characteristics of air-dried beefThe research team isolated three strains of lactic acid bacteria with strong protease hydrolysis activity from Xinjiang' s traditional air-dried meat,Lactococcus lactis(S-1),Lactococcus gracilis(S-2)and Pediococcus pentosaceus(S-3).Study the effect of adding different protease-producing lactic acid bacteria on the physical and chemical(moisture,p H and TBARS),color,texture,microorganisms and biogenic amines during the fermentation of dried beef.The results showed that protease-producing lactic acid bacteria could significantly reduce the p H value and TBARS value in the dried beef samples,improve the color of the products,inhibit the growth of putrefied bacteria(Enterobacter)(P<0.05),and effectively inhibit the accumulation of biological amines(putrosine,corpylamine,histamine,tyramine).Therefore,the addition of protease-producing lactic acid bacteria can improve the sensory quality to a certain extent,and effectively improve the safety characteristics of the product.2.Effects of protease-producing lactic acid bacteria on the degradation of air-dried beef proteinThe purpose of this study was to determine the effects of protease-producing lactic acid bacteria on non-protein nitrogen,amino nitrogen,TCA soluble peptides and free amino acids(FAA)during the fermentation and storage of dried beef.The results showed that the contents of non-protein nitrogen(NPN),aminopeptide nitrogen(AAN),and TCA soluble peptides gradually increased with the progress of fermentation,and the free amino nitrogen of each group increased significantly,but there was no significant difference between the groups.In addition,the protease-producing lactic acid bacteria promoted the release of free amino acids in dried beef.The highest total free amino acid content of the final product was S-1,reaching577.68 mg/100 g.SDS-PAGE showed the degree of protein degradation by the protease-producing lactic acid bacteria.The electrophoretic pattern bands of each group changed significantly before and after fermentation.The final degree of degradation of dried beef in the experimental group was significantly higher than that of the CK group,and the S-1group had the highest degree of degradation.3.Effects of protease-producing lactic acid bacteria on the oxidation of air-dried beef proteinProtease producing lactic acid bacteria was studied in the process of dried beef fermentation and storage protein oxidation index(carbonyl value,sulphur,protein surface hydrophobic effect),protein molecular interactions(hydrogen bonding,disulfide bond,hydrophobic interaction)and protein secondary structure(-helix,?-sheet,?-turn and random coil).It was demonstrated that the content of ionic bond and hydrogen bond in beef protein decreased significantly(P<0.05),while the content of hydrophobic interaction and disulfide bond significantly increased(P<0.05).Compared with the control,the content of carbonyl group and surface hydrophobicity in protein of S-1 group were significantly decreased(P<0.05);the content of total sulfhydryl group in S-2 group was increased significantly(P<0.05).Furthermore,the addition of protease-producing lactic acid bacteria LAB significantly reduced the ?-sheet content of myofibril protein(P<0.05).It can be seen that the treatment of protease-producing lactic acid bacteria can significantly change the chemical force of beef protein and the structure of myofibril protein.Among them,Lactococcus lactis(S-1)has the potential to become an antioxidant starter in dried beef.