Modification of soy protein using the plastein reaction, phosphorylation, and ethylation, and their effects on functionality.

摘要

Soy protein isolate was modified using enzymatic hydrolysis and the plastein reaction. Soy protein and plastein were each also chemically modified by phosphorylation and ethylation. Only 34% of the hydrolysate's nitrogen was incorporated into the plastein. Increasing the substrate concentration from 30 or 40% to 50%, and the temperature from 37;Seven functional tests were done at pH 7.0 and 4.5 to evaluate the enzymatically and chemically modified samples. Plastein functionality was found to be intermediate between soy protein and hydrolysed soy protein, except in oil related functional properties, such as oil binding capacity, emusifying capacity, and emulsion stability, where it was superior to both.;Phosphorylation generally improved most functional properties for both protein and plastein, while ethylation generally decreased functionality for each. The chemically modified plasteins however showed some functionality contribution from the plastein reaction and some from the chemical modification, resulting in some interesting functionality. Functionality testing at pH 4.5 showed a nearly uniform decrease from pH 7.0 testing for the protein samples, but the plastein samples had mixed results. The protein chemical modifications had very similar effects on water binding capacity, foaming capacity, and emulsin stability, with phosphorylation causing a small increase, and ethylation a large decrease in each case. Also, oil binding capacity and emulsifying capacity were found to be related for the chemically modified plasteins.