The Role Of Disulfide Bonds In Different Protein Emulsions And Emulsion Protein Composite Gels

The gelation of myofibrillar protein and the effects of fat and moisture are responsible for the formation of composite system in the traditional meat products.The formation of myofibrillar gel plays an important role in maintaining the functional properties of meat.Meanwhile,fat and moisture are associated with the unique flavor and taste.However,in the processing and storage of meat products,oxidation of fat will occur,and then undermine the product quality and acceptability.Because of it,which is the emulsification between protein and fat,are applied to part of new products,so it can achieve a better taste and improve the functional properties instead of animal fat.But the protein-liquid emulsions are extremely unstable,which are influenced by the type of protein and grease,intermolecular force,the conditions of environmental and emulsification and so on.The effects of intermolecular focused on protein emulsions is relatively few,while the literature on the effects of sulfhydryl groups and disulfide bonds is less.In this paper,NEM is used as a thiol blocking agent,so whether disulfide bonds are formed or not were studied on different protein-stabilized emulsions and emulsion-filled protein gels,which aimed to provide a theoretical basis for improving the quality of new meat products.1.The formation of myofibrillar gel heated at different temperatures was studied.The results showed that heating could lead to changes in the intermolecular force,structure and physicochemical properties of the gel,which were interrelated and affect each other.And the increase in the ?-helix,the increase in the ?-sheet and the presence of the torsion-twist-trans conformation in the disulfide bond are inseparable from the formation of the gel.50?,the myofibrillar protein completely formed the gel,and then disulfide bonds were just responsible for the stability of gel structure.At 60?,the gel strength achieved the highest(P<0.05),reaching 1.12 ± 0.02 N,and as the same with the total amount of disulfide bonds in the formed gel,which was 1.18±0.04 mol/1000 g protein.Therefore,it could be considered that the thermal-induced gel at this temperature is most suitable as the protein network matrix in the emulsion-filled protein gels.2.In order to explore the role of sulfhydryl groups and disulfide bonds in different protein-stabilized emulsions,NEM was added as thiol blocking agent,the effects of thiol and disulfide bonds on the properties of different emulsions were explored.It showed that the protein molecules dispersed in the protein-stabilized emulsions could form a layer of interfacial protein membrane on the surface of the oil droplets by aggregation,and the viscoelasticity of the interface protein membrane could affect the series of properties of the protein emulsions.The addition of NEM to block the sulfhydryl groups results in a reduction in the content of disulfide bond,which were able to destroy the internal structure of the protein molecule,and the hydrophobic groups were exposed to the interior,resulting in increased surface hydrophobicity.The reduction of protein emulsifying activity and emulsifying stability and destruction of protein emulsions nature also occurred.At the same time,the intermolecular interaction of the protein on the oil droplet interface protein membrane was destroyed,and the droplet size increased with the decrease of the disulfide bonds.Although blocking the formation of thiol and disulfide bonds in the three protein emulsions,myofibrillar protein,egg white protein isolate and soybean protein isolate,were similar,the degree of impact was different.3.Different protein emulsions were added to the stable myofibrillar protein solution and heated to form a composite gel,in order to simulate the meat emulsion.The effects of sulfhydryl groups and disulfide bonds on the different emulsion-filled protein gels were researched.In conclusion,sulfhydryl groups and disulfide bonds could change the properties of the membrane particles,affect the interaction between the interface protein membrane and the continuous phase matrix,and ultimately affect the gel strength,water retention,rheology and water distribution of the composite gels.Because of the addition of NEM,which block sulfhydryl groups to form disulfide bonds,the interface protein membrane of emulsion particle in the composite gels was damaged and the degree of rupture was sharply associated with the increase of disulfide bonds.The decrease of gel strength,water holding capacity,G' were happened.What's more,the distribution of moisture was much looser.