Effect Of Fatty Acid Saturation On Emulsifying Properties And Gel Properties Of Salt-soluble Protein In Pork

The study object of this paper is the salt-soluble protein of pork.In this paper,by changing the saturation of fatty acids?oleic acid,linoleic acid and linolenic acid?,combined with interfacial rheology,low field nuclear magnetic resonance and raman spectroscopy,the adsorption changes of fatty acid surface protein molecules during emulsification were studied.By establishing the relationship between the emulsification properties and the interfacial protein membrane,thereby revealing the interaction between protein molecules and fatty acids of different saturation levels and the changing properties of protein emulsified gels.Finally,the intrinsic link between protein-fatty acid,interfacial properties and emulsifying properties during protein fatty acid emulsion formation was elucidated.The main findings are as follows:1 As the fatty acid saturation decreases,the emulsion stability of the emulsion gradually decreases.The particle size of the emulsion was compared with the particle size of the fatty acid particles obtained after the emulsion system was destroyed.Both of them showed the oleic acid group<linoleic acid group<linolenic acid group,and the difference between the three groups was significant?P<0.05?.The results of unit interface membrane protein surface loading??s?were oleic acid group>linoleic acid group>linolenic acid group.It indicates that the more unsaturated double bonds,the larger the particle size after emulsification,and the less the content of protein absorbed by the unit interface film,the worse the emulsion stability.The results of fluorescence spectroscopy showed that the endogenous fluorescence spectrum of the treatment group was red-shifted,and the exogenous fluorescence spectrum was blue-shifted,indicating that the hydrophobicity of the protein after emulsification increased.Quantitative analysis of the secondary structure of the protein indicated that the emulsification process involved a decrease in the?-helical structure and an increase in the?-sheet structure.The results of gel electrophoresis showed that the oil-water interface of the oleic acid group adsorbed more protein than the linoleic acid group and the linolenic acid group.Correlation analysis showed that the?-helix of protein secondary structure in emulsion was positively correlated with fatty acid saturation and emulsion stability.The?-helix of the protein secondary structure in the emulsion was significantly positively correlated with the unit interface membrane protein surface loading??s?and the total interface membrane protein surface loading??_T??P<0.05?.The random coil content of the protein secondary structure in the emulsion was significantly positively correlated with the D10 and D50values of the emulsion particle size?P<0.05?and the D90 value was significantly positively correlated?P<0.01?.It indicates that the higher the saturation of fatty acid,the higher the content of?-helical structure of protein in the emulsion,and the higher the amount of fatty acid adsorbed protein,the better the emulsion stability of the emulsion.The larger the particle size of the emulsion particles,the higher the random crimp content of the protein in the emulsion.2 After emulsification of fatty acids of different degrees of saturation and salt-soluble proteins,the surface hydrophobicity of the protein shows oleic acid group>linoleic acid group>linolenic acid group.The Interface pressure???of oleic acid,linoleic acid and linolenic acid groups increased with the increase of adsorption time,indicating that the salt-soluble protein gradually adsorbed to the oil-water interface.And the elastic modulus?E_d?increases rapidly and then decreases,the viscous modulus?E_V?gradually increases,and the phase angle?tan??of the oleic acid group increases at a later stage,while the other two groups are relatively stable and have a small numerical value.This indicates that the adsorption of protein at the oil-water interface forms a viscoelastic film dominated by elasticity.The lower the fatty acid saturation,the more obvious the elastic characteristics.With the increase of shear rate,the shear stress of the emulsion of the treatment group increased slowly and then increased rapidly,while the viscosity decreased rapidly and finally stabilized.The shear stress and apparent viscosity are both oleic acid group>linoleic acid group>linolenic acid group.The storage modulus exhibits the same tendency as the oleic acid group>linolenic acid group>linoleic acid group.The phase angle?Tan??of the treatment group has the same change trend,and the overall trend is to decrease rapidly and then slowly decrease,and the overall feature is elastic characteristics.Therefore,the higher the degree of fatty acid saturation,the stronger the surface hydrophobicity of the protein after emulsification,and the greater the interfacial pressure???at the oil-water interface,the more pronounced the elastic characteristics of the formed interface protein film.3 As the fatty acid saturation decreases,the water retention and gel strength of the gel formed by porcine salt-soluble protein and fatty acid gradually decrease.And the relaxation times T_2bb and T₂₂2 gradually decreased,while the relaxation time T₂₁1 of the three treatment groups did not change significantly.The relaxation time T_2bb in the linolenic acid group increases and the T₂₂2 decreases as compared with the oleic acid group.And the relaxation time peak area ratios P_2bb and P₂₁1 gradually decrease,while P₂₂2 gradually increases.Correlation analysis showed that with the decrease of fatty acid saturation,the binding ability of salt-soluble protein to bound water in emulsion gel was weakened,and the binding ability of salt-soluble protein to poorly fluid water and free water in emulsion gel was enhanced,and the water with poor fluidity was converted into free water.Therefore,the saturation of fatty acids during the emulsification of salt-soluble proteins and fatty acids has a great influence on the water distribution state and migration law and gel properties of the emulsified gel.And the oleic acid group has better emulsification characteristics.