Kinetics Of Cathepsin L And Transglutaminase Activity During Dense Phase Carbon Dioxide And Heat Treatment

Transglutaminase(TGase)and cathepsin L are the main enzymes that affect the gel properties of surimi products.The former is the main enzyme that enhances the gel strength of surimi products,and the latter is the main enzyme that reduces the gel strength of surimi products.In previous studies,dense phase carbon dioxide(DPCD)was used to induce shrimp surimi to form a gel.And its quality was significantly better than that of traditional heat-induced shrimp surimi gel,but the mechanism of change was not yet clear.In this study,based on previous studies,the kinetics of TGase and cathepsin L activities in DPCD and heat treatment(boiling water)were studied,with the gel-related TGase and the gel degradation related cathepsin L as the objects.It provide basic data to elucidate the mechanism of DPCD inducing shrimp surimi to form high-quality gel,and also provides theoretical basis for the application of DPCD technology in the processing of surimi products.The main research and analysis results are as follows:(1)Taking the crude enzyme solution of cathepsin L as the research object,the kinetics of enzyme activity change of cathepsin L during the heat treatment was studied.The results showed that the enzyme activity of cathepsin L at 35 ? conforms to the first-order kinetic model,and the enzyme activity of cathepsin L at 40-60 ? conforms to the biexponential kinetic model.The heat treatment can denature and inactivate cathepsin L.Using reasonable heating temperature and speed can reduce the gel degradation caused by cathepsin L.(2)Taking the crude enzyme solution of cathepsin L as the research object,the kinetics of enzyme activity change of cathepsin L during DPCD treatment was studied,and the difference between DPCD and heat treatment on the activity of cathepsin L enzyme was compared.The change of DPCD treatment pressure on the activity of cathepsin L conforms to the first-order kinetic model;the change of DPCD treatment temperature on the activity of cathepsin L corresponds to the first-order kinetic model at 35 ?,while the activity change of cathepsin L at 40-60 ? was suitable to be described by a biexponential kinetic model.Compared with heat treatment,DPCD treatment is easier to inactivate cathepsin L.(3)Taking TGase as the research object,the influence of temperature and p H on TGase activity was investigated.The results showed that the optimal temperature of TGase was about 50 ?,and the thermal stability is best at 35?55 ?;the optimal p H was about 5.0,and the p H stability is best at 4.0?7.0;the kinetics of TGase enzyme activity during thermal processing was studied.The results showed that: the change of enzyme activity of TGase by heat treatment conforms to the first-order kinetic model.(4)Taking TGase as the research object,the kinetics of TGase enzyme activity during DPCD treatment was studied,and the differences between DPCD and heat treatment on TGase enzyme activity were compared.The results showed that: DPCD treatment pressure and treatment temperature change of TGase enzyme activity conforms to the first-order kinetic model.Compared with heat treatment,DPCD is not easy to inactivate TGase.