Improvement Of Emulsifying Properties Of Peanut Protein Isolate And Soybean Protein Isolate By Glycation Reactions

It was reported that the functional properties of protein could be modified by glycation reaction. In order to find a new use of the peanut/soybean cakes, the effect of glycation reaction on the emulsification of peanut protein isolates and soybean protein isolates were studied in this thesis.First, the properties of the protein isolates from different sources were researched. Protein isolates were prepared from peanut/soybean cakes by resolving and precipitating in alkaline and acetous distilled water. The hydrophobicity, nitrogen solubility, emulsifying activity and emulsion stability were investigated. The result of analysis showed that protein isolate from high-temperature pretreatment peanut/soybean cake had lower nitrogen solubility, and higher hydrophobicity, emulsifying activity and emulsion stability compared with low-temperature pretreatment protein isolates. The change of molecular weight was demonstrated by SDS-PAGE and HPLC.Then, the effects of glycation reaction on the emulsification of peanut/soybean protein isolates were discussed in detail. The protein isolates reacted with glucose and maltose in different heating temperatures, different ratio of protein and sugar, and emulsion activity, emulsion stability were investigated. The results showed that glycated protein has a higher emulsion activity and emulsion stability compared with raw peanut/soybean protein. The reactivity of glucose was higher than maltose. A better emulsion capabilities were obtained when the ratio of protein and sugar is 1:2, the temperature is 60℃.The emulsification of glycated soybean/ peanut isolates were compared with that of some commercial soybean proteins and sodium caseinate. The results showed that the emulsifying activity and emulsion stability of glycated protein was higher than that of commercial soybean proteins and lower than that of sodium caseinate.On the basis of work before, the relationship between protein functional properties and structures were studied. The emulsion activity increased with the increasing of attaching degree, but it was not the higher the better. There was also a relationship between emulsion capabilities and solubility, hydrophobicity...