Effect of heat treatment on solubility, surface hydrophobicity and structure of rice bran albumin and globulin

Abstract

The effect of heat treatment on solubility, surface hydrophobicity and structure of rice bran albumin and globulin were characterised. The differential scanning calorimetry (DSC), FT-IR and Raman spectra were used to analyse the effect. The results of DSC analysis showed that albumin denatured after a thermal pre-treatment of 70 °C, while globulin denatured at 90 °C. The solubility of albumin sharply decreased after heat treatment, while the solubility of globulin decreased by up to 100 °C. The results of FT-IR demonstrated that heating globulin generally increased the content of α-helix and β-turn structure, but reduced β-sheet and random coil structures, while heating albumin produced a pronounced increase in α-helix and β-sheet structures from random coil and β-turn structures. Heating albumin decreased regions around 33 kDa but increased relative band intensity around 45-53 kDa in SDS-PAGE pattern, while heating globulin up to 90 °C caused losses in bands around 20 and 50 kDa. Raman spectrogram showed that heating albumin induced a slight decrease in intensity of the Trp band. However, the Trp band of heated globulin did not change.