Effect Of Pyrophosphate-Induced Pork Actomyosin Dissociation On TGase Cross-Linking Reaction

Transglutaminase?TGase,EC 2.3.2.13?is now widely used in the processing of meat products to improve the quality of meat products.It can catalyze the intramolecular and intermolecular cross-linking of proteins,thereby improving the functionality of proteins.The cross-linking effects of TGase are closely related to the structure of substrate proteins.Previous Studies showed that structure changes caused by protein oxidation altered the cross-linking pattern of TGase.As a food additive commonly used in meat products,the influences of actomyosin dissociation and protein structure changes induced by pyrophosphate?TSPP?on the cross-linking pattern of TGase is still unclear.Moreover,common effects of TSPP and protein oxidation often occurring in the storage and processing of meat products on the cross-linking pattern of TGase is also unknown.Therefore,it is necessary to study the effects of the dissociation of natural and oxidative actomyosin caused by TSPP on the cross-linking pattern of TGase in order to provide a theoretical basis for the application of TGase in meat products and the quality control of meat products.In this study,actomyosin was used as the research object.The effects of the dissociation of natural and oxidative actomyosin caused by TSPP on TGase cross-linking were studied after treated with TSPP,hydroxyl radical oxidation system?0.01 mmol/L Fe Cl3,0.1 mmol/L ascorbic acid,1?5?10?20 mmol/L H₂O₂?and TGase?E:S=1:20?.The main research contents were as follows: Effects of TSPP on the dissociation of natural and oxidative actomyosin;Effects of TSPP-dissociated actomyosin on the cross-linking pattern of TGase;Effects of cross-linking pattern changes of TGase induced by TSPP on the gel performance of actomyosin;Correlations between oxidation degree,dissociation degree,the cross-linking pattern of TGase and gel performance of actomyosin.Effects of TSPP on the dissociation of natural and oxidized myosin showed that the dissociation degree caused by TSPP increased first and then decreased with elevated concentration of H₂O₂.The dissociation degree of sample at 1 mmol/L H₂O₂ was highest,while that of nonoxidized sample was lowest.TSPP inhibited the dissociation of actomyosin induced by ATP.Effects of actomyosin dissociation caused by TSPP on the cross-linking pattern of TGase showed that the cross-linking degree of all amples with various oxidation degree?1,5,10 and20 mmol/L H₂O₂?was promoted by TSPP.The cross-linking degree mediated by TGase was negatively correlated with the degree of oxidation for both TSPP-untreated and-treated samples.The cross-linking site mediated TGase changed from S1 to S2 with the increase of oxidation degree.For nonoxidized sample,the main cross-linking site was S1,while for severely oxidized sample,the main cross-linking site changed to S2.Compared with the–TSPP samples,the transition rate from S1 to S2 was slower than +TSPP samples.Effects of cross-linking pattern changed of TGase induced by TSPP on the gel performance of actomyosin showed that the elastic factor?EI?value,macroscopic viscosity factor?MVI?value and water holding capacity of +TSPP samples were all higher than –TSPP samples.EI value,MVI value and water holding capacity of both –TSPP and +TSPP samples further inceased after TGase treatment.The gel performance improvement caused by TGase catalysis was related to oxidation degree.The EI final value amplification of –TSPP samples induced by TSPP decreased from 88.2% to 1.86% with the increase of oxidation degree,while that of +TSPP samples ccdecreased from 90.82% to 31.25%.It can be seen that protein oxidation inhibited the enhancement of gel performance caused by TGase,and the inhibiting effect of –TSPP was stronger than +TSPP.Correlations between dissociation degree,the cross-linking pattern of TGase and gel performance of actomyosin showed that the TGase cross-linking degree of –TSPP samples was significantly related to the changes of myosin heavy chain?MHC?induced by oxidation?P<0.05?,while that of +TSPP samples was significantly correlated with the changes of both MHC and actin?P<0.05?.The gel performance of both –TSPP and +TSPP samples were correlated with myosin changes induced by oxidation and TGase?P<0.05?.When formation of gel,the aggregation and cross-linking of myosin head S1 played a key role.In summary,this study clarified effects of the dissociation of actomyosin induced by TSPP on TGase cross-linking pattern and subsequent gel performance,and analyzed the correlations between the dissociation of actomyosin,the cross-linking pattern of TGase and gel performance of actomyosin,providing a theoretical basis for the application of TGase andother cross-linking enzymes in meat products.