Effect And Mchanisms Of Ultrasound Treatment On The Stability Of Sodium Caseinate Prepared Pre-emulsified Soybean Oil

In the processing of low-temperature emulsified meat products,the application of pre-emulsification technology to use non-meat protein to replace animal protein to wrap fat globules,and use pre-emulsified vegetable oil to replace animal fat to change the fatty acid composition.The kinetics of the pre-emulsion system prepared in the actual production process is unstable,and the oil content is high(>50%),and it is prone to stratification.Ultrasound is a relatively novel emulsification processing technology that can improve the physical stability of the pre-emulsion.However,the chemical stability of ultrasound treatment pre-emulsion in high oil still needs to be evaluated.At the same time,the pre-emulsion contains non-meat protein,and the structure of the protein is modified by ultrasound.The emulsion stability mechanism needs to be further explored.In order to make the pre-emulsion reach a good stable state and adapt to processing and storage,this research system explores the effect of ultrasound treatment on the physical and chemical stability of SC pre-emulsion,from the oil-water interface and the physicochemical and structural characteristics of SC reveal its stable mechanism,and provide theoretical basis and technical support for ultrasonud pre-emulsification processing.The specific research content and results are as follows:(1)In order to evaluate the effect of ultrasound on the stability of the pre-emulsion,the effects of ultrasound treatment(20 k Hz,450 W,50.42±3.13 W/cm~2)at different times(0,3,6,9 min)on emulsification properties,particle size distribution,microstructure,storage stability,thermal stability,freeze-thaw stability,fat oxidation and protein oxidation of SC pre-emulsion were studied.The results showed that the emulsifying properties of pre-emulsion treated by ultrasound were improved,especially ultrasound for 6 min,the EAI value increased significantly from 21.00 m~2/g to 61.13 m~2/g(P<0.05),ESI was enhanced,reduced the particle size of the pre-emulsion oil droplets(P<0.05).At the same time,the appearance,particle size and microstructure were determinated,the storage stability,thermal stability,and freeze-thaw stability of the pre-emulsion have been improved,indicating that ultrasound was beneficial to improve the physical stability of the pre-emulsion.The composition of saturated,monounsaturated,and polyunsaturated fatty acids of the pre-emulsion did not change significantly(P>0.05).During storage,especially ultrasound for 6 min and 9 min,POV and TBARS of the pre-emulsion were significantly reduced(P<0.05),indicating that ultrasound suppression fat oxidation of the pre-emulsion.The content of hydrogen peroxide in the liquid matrix treated with ultrasound under the same conditions increased significantly(P<0.05).In addition,the protein carbonyl and endogenous tryptophan fluorescence intensity of the pre-emulsion liquid showed that the protein of the pre-emulsion liquid was oxidized and the degree of oxidation was the highest with 9 min of ultrasound.In summary,ultrasound was beneficial to improve the physical and chemical stability of the pre-emulsion,but the protein in the pre-emulsion was oxidized,and its stabilization mechanism needs to be further explored.(2)In order to clarify the mechanism of ultrasound to improve the stability of the pre-emulsion,the ultrasound treatment(20 k Hz,450 W,50.42±3.13 W/cm~2)at different times(0,3,6,9 min)on TSI,interfacial tension,composition and content of unadsorbed and adsorbed protein,interface protein concentration,interface membrane and protein composition unadsorbed and adsorbed protein during storage of pre-emulsion were studied.The results showed that ultrasound(especially ultrasound for 6 min)reduced the TSI and interfacial tension of the pre-emulsion,and enhanced the adsorbed protein content and interfacial protein concentration.A dense and continuous interfacial protein film formed around the oil droplets of the pre-emulsion after ultrasound for 6 min.During storage,the degree of degradation of the adsorbed protein was higher than that of the unadsorbed protein,indicating that the pre-emulsion adsorbed protein oxidation can effectively inhibit the fat oxidation of the pre-emulsion.In summary,the application of ultrasound can improve the interface characteristics of the pre-emulsion,which was beneficial to the stability of the pre-emulsion.(3)In order to more comprehensive clarify the mechanism of ultrasound to improve the stability of the pre-emulsion,the ultrasound treatment(20 k Hz,450 W,50.42±3.13 W/cm~2)at different times(0,3,6,9 min)on particle size,zeta potential,composition,secondary structure,tertiary structure and microstructure of SC were studied.The results showed that the particle size of SC treated with ultrasound was significantly reduced(P<0.05),the absolute value of the potential did not change.There was no significant difference in the composition and content of SC,indicating that ultrasound treatment would not change the main structure of SC.No significant difference in the values of?-helix,?-turn,?-sheet and random coil of SC(P>0.05).The wavelength of the ultraviolet-visible absorption spectrum had a red shift,and the surface hydrophobicity and fluorescence intensity first increased and then decreased,indicating that the SC melts,changed its tertiary structure.Scanning electron microscopy showed that SC aggregates treated by ultrasound are broken into smaller fragments,and the smaller fragments caused the surface area of SC molecules to increase and formed a more uneven and disordered structure.In summary,ultrasound changed the physical,chemical and structural properties of SC,increased protein-water interactions and protein-oil interactions,thereby improving the emulsification properties of SC,which facilitated the formation of a dense interfacial film during the emulsification process and enhanced the stability of pre-emulsion.