Study on effect of acylation on thermal properties of kidney bean(Phaseolus vulgaris L.)protein isolate

The objective was to investigate the acylation-induced change in thermal properties of kidney bean protein isolate(KPI)by differential scanning calorimetry(DSC)techneques.The possible reactive amino groups of proteins,taking part in the acylation of KPI were explored.The relationships between thermal properties of acylated KPI and acylated stage were established.The data indicated that the acylation of KPI included two stages.One was the acylation of e-amino groups(N-acylation),the other was the acylation of hydroxyl groups(O-acylation).In the N-acylation stage,the degree of the N-acylation sharply increased to about 93%～94% with the anhydride levels increasing from 0 to 0.1(acetylation)or 0.2g/g(succinylation).The O-acylation(Thr,Ser)distinctly occurred only when the N-acylation was nearly completed.In the N-acylation case,succinylation led to the increases in the thermal stability,the decreases in the enthalpy changes(ΔH),while the Td and the ΔH of KPI were unaffected by the acetylation.In the O-acylation case,the acylation led to the decreases in Td of KPI,accompanied with the sharp decrease in ΔH.