Abstract: Some enzymolysis properties such as solubility, hydrolysis degree, －SH content, molecular characteristics and microcosmic morphology of high hydrostatic pressure (HHP) treated thermal denatured rice protein during hydrolysis with alcalase were investigated. The results showed that the contents of soluble rice protein and free －SH in samples pretreated at high pressure 100－700 MPa were both increased (especially at 500 MPa), compared with that of untreated samples. The ratio of soluble rice protein in the hydrolysate obtained after HHP treatment at 500 MPa followed by 120 min of hydrolysis was 73.0% compared with only 53.6% for that obtained for non-HHP treated rice protein. However, no obvious difference in the degree of hydrolysis was found. The gel filtration chromatographic analysis indicated that soluble hydrolysates with lower relative molecular mass were obtained using HHP treatment and subsequent enzymatic hydrolysis compared to direct enzymatic hydrolysis. The SDS-PAGE analysis indicated that the content of high-molecular-mass components in insoluble hydrolysates of HHP treated rice protein decreased notably, while that of low-molecular-mass components increased distinctly. As observed under a scanning electron microscope (SEM), the morphology of HHP treated rice protein was relatively loose. Therefore, the appropriate HHP treatment was beneficial to the hydrolysis of rice protein and enzymatic hydrolysis characteristics were directly associated with structural changes in rice protein caused by HHP treatment.

Key words: thermo-denatured, rice protein, hydrostatic pressure, enzymolysis, protein solubility, protein subunit