Study On The Preparation And Properties Of Sodium Soy Protein

Protein is a type of amphiphilic biological macromolecules with hydrophilicgroups and hydrophobic groups, and ideal surfactants which is mild, degradable andbiocompatible. However its surface active properties are limited, because of thefolding and coiling of protein polypeptide chains under the influence of hydrogenbond, electrostatic interactions, hydrophobic interaction and disulfide bond effect. Inaddition,2S,7S,11S and15S of native soybean protein are globulin, a majority ofhydrophobic amino acids are wrapped in the inter-molecule, so surface activeproperties of native soybean protein are poor.Soybean protein was prepared from low-cost soybean flour or bean pulp in thispaper. And then soybean protein was treated by acidic and alkaline modification, inorder to change protein structure and conformation. Finaliy, NaCl was added tochange the charge of protein, ionized, aims to improve the functional properties of soyprotein. The main results of the paper are showed as followed:1. First, the physicochemical properties and surface activity of three native soyprotein isolate from market were determined. There was small of protein contentdifference among SPI1, SPI2and SPI3, the moisture content of SPI3was lowest.Emulsibility of SPI3was higher than other soybean protein isolate and emulsibility ofSPI1was worst. Emulsion stability of SPI2and SPI2was higher than SPI1. Thehighest foaming was SPI3and SPI1, SPI2was lowest. Foaming stability of SPI3wasbest, SPI2was worst. The surface tension of SPI1, SPI2and SPI3and CMC under thesame concentration were similar, its surface tension and CMC were46.8mN.m-1and0.75g.L-1, respectively.2. Influence factors of soybean protein surface activity were discussed and thestructure change was determined. Extracted repetitiously soybean protein solutionwere mixed, then treated by acid and alkali, NaCl was added, spray dry afterneutralizing used acid. The influences of temperature, heating time and pH on thesoybean protein surface activity were investigated. The best modified conditions wasobtained through the orthogonal test: the best heating temperature was110℃, pH was8.0, and the heating time was15min, emulsibility of the modified sample increased by25.7%, the emulsion stability increased by82.03%, foaming increased by26.67%, thefoam stability increased by255.25%. When1.0%NaCl was added, the emulsibilityincreased32.87%, but the emulsion stability change little, the foaming increased33.33%and the foaming stability increased250.00%. And emulsibility of the modified sample with NaCl increased by5.70%over the modified sample with noNaCl, the foaming increased5.26%, the foaming stability change little. According tothe detecting of sulfhydryl bond, ultraviolet absorption spectrum, endogenousfluorescence scan at280nm, the modified soybean protein’s structure was verified tohave changed. And the structure change maybe was one of the reasons of the surfaceactive change3. Soybean protein was prepared from low-cost soybean flour or bean pulp, thensodium soy protein products were prepared based on the optimum modificationconditions by homogenization of the viscolizer and spray drying. Compared withcommon surfactants(such as sodium caseinate, Span-20, Tuwen-80), the resultsshowed that the emulsibility of sodium soy protein products was increased53.23%forsodium caseinate. the emulsion stability of sodium soy protein products was similar tosodium caseinate but much lower than Span20and Tween-80. Foamability of sodiumsoy protein products was similar to casein, lower than Tween-80, but increased by14.29%for Span-20. the foam stability was about70.00%and it was higher thansodium caseinate, Span-20, Tween-80surfactants.