Effects of ozonation and addition of amino acids on properties of rice starches.

摘要

In this study, the effects of ozonation and the addition of amino acids on rice starches were determined in terms of pasting properties by using rapid visco-analyzer, thermal characteristics by using differential scanning calorimeter, crystallinity by using x-ray diffraction, and resistant starch yield.;Results from viscosity analysis showed that the addition of lysine (6%) to ozonated Sigma rice starch significantly reduced peak viscosity (PV), minimum viscosity (MV), final viscosity (FV), and setback (SBK) by 918, 1024, 1023, and 105 cP, respectively. Moreover, it decreased pasting time, resulting in the faster swelling upon heating and less rigid gel formation upon cooling. The presence of lysine in ozonated white starch isolate (WSI) also significantly reduced all pasting properties and time to cook, and produced starch gel with the best cooking stability.;The amylose content of Sigma rice starch was increased by ozone, and the enzymatic-gravimetric analysis indicated that the resistant starch yield was enhanced by more than 3% when rice starch was ozonated for 30 minutes. Moreover, the addition of leucine to ozonated starch showed the highest resistant starch formation (9.13%). Ozonation of Sigma rice starch and white starch isolate (WSI) reduced gelatinization temperature, amylose-lipid complex endothermic temperature and enthalpy, but increased 1st transition enthalpy. However, the presence of lysine (6%) increased gelatinization endotherm transition temperature but reduced 2nd transition enthalpy.;Ozone treatment of Sigma rice starch induced B+V type XRD pattern and increased the relative crystallinity (RC), and addition of lysine showed A+B type XRD pattern and enhanced the RC further. In addition, ozonation caused some physical damage showing some broken small pieces of particles and distorted starch granules with both Sigma rice starch and white starch isolate.