The Effect Of TG Enzyme On Protein Emulsification Properties And Its Role In Myofibrillar Protein Composite Gels

Myofibrillar gel has a significant effect on the texture and functional properties of meat and meat products.Studies on changes in myofibrillar proteins during thermal-induced gel formation can contribute to ensure meat quality and improve the meat production process.The functional properties of myofibrillar protein are characterized by its ability to form a three-dimensional viscous gel network,cross-link the water and form a stable membrane on the surface of the fat globules in the emulsified system.These functional characteristics and the taste and appearance of meat products are closely related.Single gel meat products are unstable,and more and more consumers prefer low-fat meat products.Non-meat proteins are often used as fat substitutes in meat products,while improving the quality of meat products.The common non-meat protein are soy protein isolate,sodium caseinate and egg white protein.Another way to improve the quality of meat products is to add enzymes to catalyze the protein to react to modify the protein structure.The effects of TGase and non-meat proteins on the emulsifying properties and gel properties of myofibrillar proteins were studied.The details are follows:Firstly,the effects of the addition of TGase and different non-meat proteins(sodium caseinate,soy protein isolate,egg white protein)on the gel strength,water holding capacity,rheological properties and secondary structure of myofibrillar protein were studied.The results showed that addition of non-meat protein(sodium caseinate,soy protein isolate,egg white protein)and TGase could significantly improve the myofibrillar protein gel properties.The gel strength and water holding capacity of myofibrillar protein increased with the increase of TGase additive amount(P<0.05).The addition of TGase also improved the rheological properties of myofibrillar protein.The gel strength and water-holding capacity of egg white protein gel were significantly higher than that of casein sodium and sodium alginate(P<0.05),and the gel strength was increased with the addition of different non-meat proteins(sodium caseinate,soy protein isolate and egg white protein)directly added into myofibrillar sol.The addition of TGase and non-meat protein reduced the content of ?-helix in the amide band(1650-1680 cm-1)in the Raman band of myofibrillar protein gel,and the content of ?-sheet and turn increased significantly the content of curl also increased significantly(P<0.05),indicating that the addition of TGase and non-meat protein would effect the secondary structure of the myofibrillar gel.Secondly,we studied the effects of TGase on the emulsifying properties of protein emulsions,while the competitive adsorption properties of myofibrillar protein-non-meat protein(sodium caseinate,soy protein isolate,egg white protein)system was studied.The results showed that the emulsifying activity of myofibrillar emulsions was significantly higher than that of non-meat protein emulsions.The addition of TGase could significantly improve the emulsifying activity of emulsions(P<0.05).The emulsion stability of emulsion was time dependent,the stability of the emulsions in each group was reduced with prolonged standing time.The addition of TGase increased the apparent viscosity of each group of emulsions due to the crosslinking effect of TGase on the protein,and the droplets of the emulsions were smaller than those of the non-TGase-added components.In the competitive adsorption of non-meat proteins and myofibrils in emulsions,the results indicated that in myofibrillar proteins-non-meat protein(sodium caseinate,soy protein isolate,egg white protein)-vegetable oil emulsions,the non-meat protein is strongly attracted by the fat-water emulsion interface,competing with myofibrillar protein,and takes precedence over the myofibrillar protein to form a strong lipid surface protein membrane,giving priority to vegetable oil emulsification.Finally,the effect of TGase on the gel properties of non-meat protein myofibrillar complex gel was also studied.TGase catalyzes the formation of protein uniform gel space network structure,so as to enhance the containment of water binding capacity,while increasing the gel strength of myofibrillar protein.TGase-induced myofibrillar proteins' temperature required for the crosslinked protein to form an elastic structure was lower.From the electrophoresis banding results,the color of the gel electrophoresis bands of TGase-free gels were lighter than that of the untreated TGase,and the microstructure of the composite gel was more uniform,which was related to the relaxation time T2,and the uniform network structure restriction the movement of water molecules,and improve the water retention of the myofibrillar protein composite gel.