Effects On The Functional, Structural And Gelation Property Of Soybean Protein Isolate Treated By Ultrasound

Soybean protein isolate(SPI) is an ideal protein source, exhibits broad sources and low price,and has high nutritional value and unique features of health care. Due to denaturation, its functional properties were dissatisfied and limited in the food industry. With these factors, in this study, ultrasound was used to change the physicochemical properties of soybean protein isolate. At the same time, prepared soybean protein isolate gel crosslinked with transglutaminase(TG) enhanced by ultrasonic. As the carrier, the riboflavin was encased, and studied its controlled release of active substances. The main research contents and conclusions are as follows:(1) Ultrasonic treatment improved the solubility of soybean protein isolated;With increasing ultrasonic power, water binding capability(WBC) and fat binding capability(FBC) tended to rise, with increasing ultrasonic time WBC and FBC tended to at first rise and then fall, increased by 27.43% and 27.43% respectively;The emulsifying properties of the SPI were found to be improved by ultrasonic treatment, The foam of ultrasonic treatment was small and dense, in a short period of time will not broken and deformation; Rheological data analysis showed that the ultrasonic treatment increased the solution of soybean protein isolate storage modulus(G ’) and loss modulus(G "), but there is no significant difference between protein gel temperature of the ultrasonic processing. After ultrasonic treatmen, G ’and G" of samples were higher than the control sample, shown that ultrasonic treatment could increase the viscoelastic property of soybean protein isolated.(2) A short period of time of ultrasonic treatment could significantly reduce the average particle size of soybean protein isolate, but it would be protein aggregation phenomenon when give rise to extend the time of ultrasonic, it was a complex dynamic process. The intensity of ultraviolet absorption of the SPI solution increased after treated by ultrasonic; hydrophobic sites buried in the molecule gradually exposed, leading to increasing surface hydrophobicity, α-helix deceased, random coils increased, but the content of β-sheet and β-turn had no change. Fluorescence spectra and circular dichroism spectra analysis showed that the ultrasonic treatment could cause some protein structure change, hydrophobic groups exposure, and secondary structure change. SDS-PAGE results showed that the molecular weight, however, still not be affected.(3) It found that ultrasound could enhance the gel property, rheological property and thermal stability.Ultrasound pretreatment significantly increased free sulfhydryl content of SPI. The free sulfhydryl content of TG-catalysed SPI gels(TCSGs) decreased after ultrasound pretreatments, suggesting ultrasound facilitated the forming of ε-(γ-glutamyl) lysine isopeptide bond during TCSG formation,partiy by hydrophobic and hydrogen bond contribution, and resulted in more homogeneous and denser gel network. Ultrasonic increased the content of soybean protein isolated free sulfhydryl, promoted in the process of gel formation of disulfide bond formation. The 60 min US-TCSG had the highest gel strength, storage modulus(G’) and loss modulus(G’’), but the lowest value of tanδ. Moreover, US pretreatment also significantly increased the consistency coefficients and decreased the flow behavior index of TCSG. Differential scanning calorimetry data indicated that US pretreatment could lead to increased peak temperature(Td) and decreased enthalpy(ΔH). Pearson correlation test showed that the particle size of SPI dispersions was negatively correlated with gel strength, final G’ and Td.(4) Ultrasonic pretreatment can improve the encapsulation efficiency riboflavin gel, and with increasing ultrasonic time, encapsulation efficiency of the load riboflavin gel had better ability of embedding. In simulated gastric juice(non-enzymes) characterized by dehydration shrinkage, whereas in the simulated intestinal fluid(non-enzymes) water absorption swelling. Compared with the untreated samples, gel swelling property reduced, and corrosion resistance increased. Moreover, 400w、60min ultrasound pretreatment reduced the riboflavin release speed in gastrointestinal fluid.