Study On Factors Affecting Interaction Between Myofibrillar Protein-Wheat Protein Hydrolysate And Their Complex Emulsion System

Emulsified meat product is a important part of meat products.Myofibrillar protein in meat is a kind of important protein involved in emulsification.While in the practical processing of production and storage,there still are some quality defects in emulsified meat,such as leaking oil and water,loose structure and so on.In the process of meat emulsification,non-meat protein owns the competitive adsorption with myofibrillar protein in the oil-water interface,aiming to enhance the stability of emulsification and improve the quality of emulsified meats.Firstly,the effects of wheat hydrolyzed protein on the structure and functional properties of myofibrillar protein were explored,and then the protein complex formed by wheat hydrolyzed protein and myofibrillar protein was used as a emulsifier to prepare the complex emulsion.The effects of wheat protein hydrolysate on emulsification characteristics of non-meat protein and meat protein mixture were studied,and the effects of conditions of emulsion-NaCl,pH and temperature on the emulsification characteristics of the co-emulsifying system were also explored hoping to improve the emulsification characteristics of myofibrillar protein,and increase the emulsion emulsification and stability,for handling the problem of poor emulsification performance of emulsified meat products in the production and storage process of certain reference.The following are the major contents and results of this paper:1.As concentration of wheat protein hydrolysate increased,wheat protein hydrolysate and myofibrillar protein interacted in solution resulting in dramatically increasing of the turbidity of complex solution and the content of surface hydrophobicity and total sulphur(p<0.05).The surface tension reduced gradually at the same time.Complex D_H first decreased and then increased with a minimum at wheat protein hydrolysate concentration of 4 mg/mL.The above changes helped for the protein complex to strengthen the interference between proteins,and,adsorb onto the oil-water interface during the emulsification process which making protein interface membrane around the droplet surface to be more stable and compact.Adding adequate wheat hydrolyzed protein(0.5-4 mg/mL)obviously improved the emulsifying property of the complex emulsion.With wheat protein hydrolysate concentration increasing,the EAI,ESI and zeta-potential of complex emulsion firstly increased and then decreased.The emulsion showed the best emulsification stability at wheat protein hydrolysate concentration of 4 mg/mL,and the lowest average particle size and lactation index.Meanwhile,the droplet distribution was uniform,and the interfacial membrane thickness increased at this condition.2.When NaCl concentration increased,the turbidity,surface hydrophobicity and surface tension of the composite solution all decreased gradually,the sulfhydryl group buried in the molecule was exposed leading to the increase of free sulfhydryl group content,which was obvious at the NaCl concentrations between 0.1 M and 0.6 M(p<0.05),while the change of total sulfhydryl group content was not significant(p>0.05).When electrostatic interaction came about between myofibrillar protein and wheat protein hydrolysate,D_H of the complex protein was dramatically reduced(p<0.05).The protein complex was more easily adsorbed to the oil-water interface,and formed a dense interfacial membrane around the fat droplets.The EAI and ESI of myofibrillar protein-wheat hydrolyzed protein composite emulsion increased clearly first(p<0.05)and then decreased obviously(p<0.05).The lactation index first decreased and then increased,shear viscosity and emulsion zeta-absolute potential first increased and then decreased,the particle size of composite emulsion decreased,the distribution tended to be uniform,and the interfacial film thickness increased with NaCl concentration increasing.When the NaCl concentration was 0.4 M,the emulsion had the lowest lactation index and higher viscosity,which prevented oil droplets from accumulating and stratifying.Moreover,the emulsion zeta-potential absolute was significantly higher than that at other NaCl conditions,and the particle size distribution was significantly more concentrated than that in other groups.The average particle size was smaller,and the emulsion system was more uniform and stable.3.When solution pH increased,turbidity of the composite solution decreased first and then increased,and the surface hydrophobicity decreased obviously(p<0.05).The total and free sulfhydryl group contents both increase first and then decrease with a maximum at pH6.0.The D_H of complex protein decreased first and then increased.When solution pH was 5.5,which was close to the isoelectric point of myofibrillar,the electrostatic repulsion between myofibrillar and wheat hydrolyzed protein molecules became smaller and the complex protein D_H was obviously higher than that of the other three groups(p<0.05).The surface tension of the composite protein solution decreased gradually,and then dropped to the lowest when solution pH increased to 6.0.As solution pH increased,EAI and ESI of composite emulsion first increased and then decreased,while the lactation index and droplet size first decreased and then increased,and the zeta-absolute potential of emulsion first increased and then decreased.When the pH was at 6.0,the EAI,ESI and zeta-potentials absolute of myofibrillar-wheat hydrolyzed protein composite emulsion were the greatest,the emulsion index was the lowest,and the emulsion was the most stable.The stratification was not obvious,and the emulsion properties of the composite emulsion were better than those of other pH conditions.4.When temperature rose,turbidity of the complex solution increased gradually,D_H of protein complexes,increased first and then decreased with a minimum at 35?.Surface hydrophobic group content of complex solution,EAI and ESI of composite emulsion all decreased after rising first.Both surface tension of complex solution and lactation index of composite emulsion,however,showed opposite changing tendency and reached a minimum at35?.The microscopic analysis showed that when the temperature rosed to 35?,the droplet size decreased and the distribution of emulsion particles tended to be more uniform.The properties and status of protein complex solution and composite emulsion showed a similar changing tendency as the concentration of wheat hydrolyzed protein increaing at the same temperature.