Fabrication Of Soy Protein-based Colloidal Microstructures And Their Functional Properties

Healthy foods, which provide various nutrients and palatability for human consumers, are able to reduce the risk of getting sick. And they have been increasingly concerned in the recent years. In this study, soy protein isolate(SPI) was used as main material to fabricate various colloidal microstructures, including hydrogels, microspheres and nanoparticles, and the relationship between their structure and functionalities had been investigated. The effect of porous structure in the edible gel on the release of sucrose, and the ability of the fluid particles to modify the gel texture and the absorption of aroma substances had been studied. The main results are as follows:(1) Porous structures were fabricated in the soy protein gel via high speed homogenizing with the help of the cross-linking reaction between the protein molecules induced by microbial transglutaminase(MTGase). The gels with different structures and mechanical properties were prepared by different processing conditions of the gel, including p H, stirring and homogenization. More serum and sucrose released in the porous gel prepared at p H 6.0. In addition, more small fragments appeared after the gels with porous structure were broken, leading to greater surface area for contact with the taste buds. In other words, the inhomogeneous structure in the gel(porous structure) was able to make more sucrose release from the gel matrix the sucrose, leading to increasing the sweentness intensity of the gel.(2) Gum arabic(GA) was used to control the thermal aggregation behavior of soy protein and prepare SPI/GA fluid gel particles. Tween 80 was used to modify the surface morphology of the fluid gel during spray drying. The optimal processing conditions for SPI/GA fluid gel were as follows: SPI/GA mixed dispersion was heated at 85 °C for 30 min with stirring at 700 r/min. Afterwards, it was homogenized at 30000 r/min for 2 min, and then spray dried(inlet temperature:140°C). Fluid gels with different particle size, morphology, viscosity, dispersion and hygroscopic properties were obtained via various amount of GA and Tween 80. When SPI was used to prepare heat-set gel with the fluid gel particles, the hardness of the resultant gel was increased.(3) Soy protein-based particles were prepared by spray drying method with tannic acid(TA) which was able to modify the aggregation behavior of soy protein and the surface morphology of the obtained particle. Particles with different particle size, shape and viscosity could be obtained by adjusting the p H and processing conditions. The effects of the amount of TA on the bulk density, wetting time and insoluble index of soybean protein-based particles was not significant. The aroma adsorption of soy protein-based particles was related to their microstructure, the types of aroma components and the processing methods.