Abstract:

Rice peptides were grafted with glucose in aqueous solution under different levels of reaction temperature and time, initial pH, substrate concentration, rice peptide/glucose mass ratio in order to investigate the effects of these reaction conditions on the functional properties of the grafted products including emulsifying activity (EA), emulsion stability (ES) and reducing power. The results indicated that 1) the degree of grafting (DG), browning degree and reducing power of the graft reaction products (GRPs) increase with rising reaction temperature and prolonged reaction time. However, excessively long reaction time led to decreases in DG, EA and ES; 2) The EAs of rice peptides and GRPs were both enhanced as initial pH increased from 6 to 10, their reducing power and ES increased initially and then decreased, and GRPs showed higher levels of EA and reducing power than native rice peptides, and GRPs obtained using an initial pH of 0.798 had the highest reducing activity; 3) both the EAs of rice peptides and GRPs showed a trend to initially increase and then decrease with substrate concentration increased, and the emulsify stability and reducing power were improved remarkably; 4) The EA and ES of GRPs were obviously affected by rice peptide/glucose mass ratio, and EA was most significantly enhanced and reached up to 35.13% when the ratio was 1:2, while the ratio had no significant effect on the reducing power of GRPs.

Key words: rice peptide, grafting reaction, emulsifying activity, antioxidant activity