| At present,based on the vigorous development of soybean industry in China,the scale of soybean protein production continues to expand and the advantages of its nutritional value and economic potency are remarkable.More and more scholars have deeply discussed the aggregation and depolymerization behavior of soybean protein isolate.Meanwhile,the aggregation behavior of soybean protein isolate under heat induction has a significant effect on i ts system structure and function,so the modification of soybean protein isolate has become a hot spot in soybean deep processing.In this paper,soybean protein isolate was taken as the main research object.The mechanism of action of temperature(60?,80?,100?)and ultrasonic power(200 W,600 W)on the structure and function of soybean protein isolate was analyzed by thermal induction and ultrasonic modification.It can clarify the regulation mechanism of ultrasonic assisted heat treatment on the aggregation behavior of soluble soybean protein isolate,give full play to the technical advantage of heat induction and ultrasonic modification,and improve the quality characteristics of soybean protein isolate series effectively.To provide theoretical and te chnical support for the development and application of high functional soybean protein series products in China.The main conclusions of this study are as follows:The soluble soybean protein isolate was modified by ultrasonic-assisted heat-induced treatment.The ultrasonic power(60?,80?,100?)and ultrasonic power(200 W,600 W)were analyzed in detail.The results showed that with the increase of temperature,the particle size of soluble soybean protein isolate increased,and the solubility of soluble s oybean protein isolate decreased first and then increased.Turbidity increased first and then decreased.Ultrasonic-assisted heat treatment could significantly increase the solubility of soybean protein isolate,decrease the turbidity and increase the particle size of protein.The main findings are as follows:(1)The soluble soybean protein isolate was modified by ultrasonic-assisted heat-induced treatment.Physicochemical property and stablility mechanism of soluble Soybean protein isolate were analyzed deeply at different temperatures(60?,80?,100?)and ultrasonic power(200 W,600 W).With the increase of temperature,the particle size of soluble soybean protein isolate increased.When the soluble soybean protein isolate was treated with 200 W ultrasonic power,the particle size increased.However,the particle size decreased and a larger range of peaks was formed at 1000 nm when the soluble soybean protein isolate was treated with 600 W ultrasonic power.The soluble aggregates of soybean protein isolate formed at 60?,80?and100?were treated with ultrasound at low power and high power It was found that the particle size of soluble thermal aggregate of soybean protein isolate increased and the increasing trend of soluble aggregate particle si ze is more obvious with the increase of temperature at the same power.When the soybean protein isolate was heated,the solubility of soluble protein decreased with the increase of heating temperature.When the soluble soybean protein isolate was treated by ultrasound,the solubility of soluble soybean protein isolate increased under the condition of low power 200 W and high power 600 W ultrasonic treatment.Low power(200 W)and high power(600 W)ultrasonic treatment of soluble soybean protein isolate aggregates formed at heating temperature of 60 ?,80?and 100? respectively showed that the solubility of soluble thermal aggregates increased.After heat treatment,the turbidity of soluble soybean protein isolate increased with the increase of heating tem perature.(2)The effect of ultrasound assisted heat induction treatment on molecular weight and structure characteristics of soluble soybean protein isolate was deeply analyzed by Size exclusion chromatography,Fourier transform infrared spectrum,Fluorescence spe ctrum,SDS-PAGE gel electrophoresis and atomic force microscopy analysis,and the mechanism of regulation of soluble aggregation of soybean protein isolate by ultrasonic combined heat treatment was clarified.It was found by size exclusion chromatography that the content of soluble aggregates increased as the heating temperature increased and the ultrasonic power increased.When the heating temperature is 100?,the content of the small molecule polypeptide increases.Low-high-power ultrasonic treatment of soluble soy protein isolate at different heating temperatures showed that the content of soluble soy protein isolate aggregates increased.As the power increases,the product having a molecular weight of less than 1.6 KDa almost disappears.Fourier transfor m infrared spectroscopy analysis shows that heat treatment can promote the disordered conversion of protein secondary structure.Soluble soy protein isolate and heat-induced soluble protein were sonicated at different powers.It was found that the ?-sheet content of soy protein isolate was decreased and the random structure content was increased.After heat treatment of soy protein isolate,the hydrophobicity of the soluble protein surface increases.When the low-and high-power ultrasonic treatment of soluble aggregates under different temperature heating conditions,the surface hydrophobicity of the soluble aggregates increased.SDS-PAGE analysis showed that under heating conditions,?,? subunit and B basic subunit of soy protein isolate were involved in the formation of soluble aggregates.Sonication of the soluble protein after heat treatment showed that with the increase of the intensity of ultrasonic treatment,the content of ?' subunit of 7S protein increased significantly,the content of ? subunit decreased significantly,and the content of B subunit of 11 S protein decreased.It was found by atomic force microscopy that the particle height range increased with heating temperature under heating conditions.When the heating temperature is 100 ?,a large number of small-sized particles are formed.Ultrasonic treatment clearly promoted aggregation.(3)The emulsification activity,particle size,zeta potential and optical microscopy analysis of the emulsion were used to analyze the characterization of soluble soy protein isolate at the emulsion interface.As the heat treatment temperature increases,the emulsification of the protein shows an upward trend.Ultrasound-assisted heat treatment promotes the emulsification of soluble soy protein isolate.the particle size analysis of the emulsion shows that as the temperature increases,the particle size of the emulsion increases and the uniformity decreases.Ultrasound-assisted heat treatment promoted the emulsion stability of soluble soy protein isolate,and the emulsion particle size decreased significantly.Through the surface potential analysis of the emulsion,the heat treatment enhances the electrostatic repulsion between the oil droplets.At the time of sonication,as the ultrasonic power is increased,the electrostatic repulsion of the protein is further enhanced.After analysis by optical microscopy,the emulsion became flocculated under natural conditions,and a large number of oil droplets flocculated and agglomerated severely.At the time of heat treatme nt,the degree of coalescence of the oil droplet agglomerates is lowered.After sonication,the droplets were evenly distributed,and the emulsification effect was significantly improved after ultrasonic treatment. |
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