Microparticulation Of Soybean Protein Isolate

From the perspective of environmental friendliness,green processing and sustainable development,it is urgent to develop food protein ingredients derived from plant-based protein sources in order to meet the growing market demand for high-protein foods.In this research,soy protein isolate(SPI),a by-products of bulk grain and oil processing,was used to prepare protein micro-particulates by high-temperature shearing and spray drying.The stability of soy protein micro-particulates under different pH conditions and heat treatment was investigated.In addition,egg albumin is added to particulates during the preparation process to further improve their physicochemical properties.The possibility of applying protein micro-particulates as a new generation of plant protein ingredients in high-protein foods was investigated.The main conclusions are as follows:(1)SPI was subjected to high-temperature shearing and spray drying treatment under different pH conditions,and protein micro-particulates distributed from 2 to 100 ?m were obtained.As prepared at pH condition more close to the isoelectric point of SPI(pH 4.5),the resulting micro-particulates had a higher degree of density and internal protein content,and the spatial structure became more compact.The size distribution,protein leakage and apparent viscosity of protein micro-particulates did not significantly change while the pH environmental changed.These particulates had shown a good thermal stability.Micro-particulation process could block the hydrophobic groups and hydrogen bonding sites of protein molecules,weakening the interaction between the particles,which resulted in the decrease of the apparent viscosity and the gelation properties.The structure of protein micro-particulates maintained folded during heat treatment.The high-pressure micro-fluidization homogenization treatment produced a mechanochemical effect on the soy protein micro-particulates,leading to a smaller size(1-10 ?m)and more regular shape(sphere)of particulates.It also significantly reduced the apparent viscosity of the protein micro-particulates dispersion.(2)In order to further improve the functional properties of protein micro-particulates,we added egg albumin to soy protein micro-particulates during the preparing process,so as to form more covalent disulfide bonds in these micro-particulates.With the addition of egg albumin and the extension of the time for heat treatment,the content of free sulfhydryl group decreased while the content of disulfide bond increased,resulting in a further decrease of viscosity and weakened gelation properties of the micro-particulates dispersion,which still did not form heat-induced gel as its concentration reached 15%.Compared to soy protein micro-particulates,the complex protein micro-particulates had better and smooth mouth-feel.The micro-particulation process could also reduce the amount of volatile flavors in soy protein and improve its smell.A low-viscosity but high-protein plant beverage can be prepared by adding this complex protein micro-particulates to pea protein beverage.After re-homogenization,the product maintained stable and did not precipitate after it was stored for 10 days.(3)Soy protein gel was prepared by acidification of glucono-?-Lactone(GDL),in which SPI was partly replaced by complex protein micro-particulates,and the effects of micro-particulates on the gel network formed by soy protein were investigated.The results of rheological and mechanical properties showed that the complex protein micro-particulates could significantly reduce the strength of acid-induced gel of the soy protein.