Preparation And Properties Of Acetylated SPI And Carboxyl Propionylated SPI

Recently, soybean protein isolated (SPI) has been paid attention to as a novel material. In this study, we prepared acetic acylated SPI and carboxyl propionylated SPI (CPSPI) using acetic anhydride and succinic anhydride. The degree of acylation of SPI was conformed by the ninhydrin-based method and the conductivity-based method. And the change of structure was characterized by Fourier transform infrared spectrometer (FTIR). And then we determined the isoelectric point (IEP), relative viscosity, solubility, conductivity,and gel properties.The results demonstrated that degree of acylation (DA) of SPI increased along with the reaction time and the quantity of anhydride. We also found that the degree of acylation had close relation with pH, which was largest at pH 12.The change of solubility of acetic acylated SPI was not very big and the decreased isoelectric point was gotten, however, acetic acylated SPI enhanced the aqueous solubility of native soy isolate. CPSPI improved the solubility of unmodified SPI in neutral and basic condition, although it is almost the same in the acidic circumstance. The change of IEP is not as notable as the acetic acylated SPI. We got the gels with good swelling ability using the crosslink of glutaraldehyde (GA).We also found that the molecular-weight average of number could be calculated by the ninhydrin-based method or conductivity- based method. The results of DA based on ninhydrin method were not bigger than 5% compared with the conductivity-based method, and for the molecular- weight, the difference was not more than 2%.