Effect Of Ultra High Pressure(UHP)treatment On The Physicochemical Properties Of Indica Rice Starch

Quality characteristics and structures of indica pre-treated by ultra-high pressures（UHP,100-600 MPa）and steaming were investigated in this research.In the experiment,physical modification of starch in indica was processed to transform it into resistant starch in order to reduce the glycemic index of indica.In the experiment,the treatment method of indica was determined first,and the blood glucose production index was measured at 300 MPa.Compared with indica rice flour itself,its glycemic index is the lowest.The LF-NMR results and morphologies of indica grain showed that UHP treatment promoted uniform distribution of water in indica.Compared with untreated indica rice,amylose dissolution was dramatically decreased by pressurization at 300MPa.DSC results showed that onset gelatinization temperature（T_o）of rice flour decreased after UHP treatment.And the degree of starch gelatinization（DSG）presented an decrease at 100 to 300 MPa,but opposite trends were found at 400-600 MPa.From FT-IR Spectromete the peaks intensity decreased with increasing pressure from 100 to300 MPa,while processed with excessive pressure（over 300 MPa）peak intensity will increase instead.Scanning electron microscopic images showed that the morphology of starch in rice changed and lost polygonal shape after UHP treatment and steaming.As the pressure increased from 400 MPa to 600 MPa the number and the width of gaps in indica are further reduced.Total analysis of the ¹³C CP/MAS NMR spectra showed the similar result that excessive pressure（600 MPa）will inhibit starch gelatinization.