Effect Of⁶⁰Co Radiation On The Properties Of Rice Flours And Their Starches

In this paper, the glutinous rice flour and its rice starch, indica rice flour andits starch were selected as the material. The doses of0KGy、5KGy、10KGy and15KGy from60Co rays were applied to irradiate these samples. The samples irradiated were analyzed using colorimeter, scanning electron microscopy, X-ray diffraction, viscosity. We observe the changes in color of rice flours and starchs after the radiation, particles apparent characteristics, crystal properties, rheological properties and free radical. The main results were as follows:1. Using different doses of60Co rays to irradiate on rice flour and its starch, and then the change of L, a and b values was observed, there is no change for0KGy, glutinous rice flour’s L value reduced7.22, a value increased3.38and b value increased9.25for10KGy radiation, respectively, but the its starch’s L value reduced14.85, a value increased2.98and b value increased4.29, respectively. For indica rice powder, L value decreased5.82, a value increased2.42, b value increased8.27, respectively. Indica rice starch’s L value reduced10.52, a and b value increased respectively2.97and5.72.2. The optical morphology of rice flour and its starch was observed by SEM. The surface on rice flour and its starch do not change obviously with the increase of the dose(0～10KGy). After irradiation in dose10-15kGy, the surface on rice starch occurred small-scale pit, what’s more, the indica rice starch with small holes on the surface. We suggested the irradition resulted in the changed in intermal structure of the starch, the cystic structure might be destroyed, so the pit and pore had happened.3. Compared with the viscosities among glutinous rice flour and its starch, indica rice flour and its starch. It showed that the viscosity values decreased with the increasing radiation doses. According to radiation doses of0KGy,5KGy,10KGy and15KGy, the viscosity value of3%samples treated by irradiation reduced respectively from64.3to55.9mPa.s for glutinous rice flour, from64.8to50.7mPa.s for glutinous rice starch, and from61.3to45.3mPa.s for indica rice flour, from55.6to40.4mPa.s for indica rice starch. In comparison, the viscosity value of1%samples treated by irradiation reduced respectively from60.5to54.2mPa.s for glutinous rice flour, from56.8to40.2mPa.s for glutinous rice starch, and from57.7to35.7mPa.s for indica rice flour, from52.6to32.5mPa.s for indica rice starch.The viscosity’s downward trend is relatively flat with the concentration of3%,and the viscosity value did not have obvious decrease while the concentration of1%of the samples’viscosity decreases faster when the dose up to10kGy.Overall, the sample viscosity of3%was always higher than the sample viscosity of1%, viscosity downward trend did not as obvious as the sample of1%. Of all,indica rice starch viscosity decreased the fastest.4.Compared the solubility of the glutinous rice flour and starch, indica rice flour and starch by different temperatures and radiation doses.The results show that the solubility increases with increasing radiation doses.the order of radiation doses was OkGy,5KGy,10KGy and15KGy.At Temperature of30℃,The solubility increased from3.088%to4.391%for glutinous rice flour, from0.709%to2.296%for glutinous rice starch, and from1.257%to2.249%for indica rice flour, from0.656%to2.838%for indica rice starch.At Temperature of70℃,the solubility increased from3.823%to5.252%for glutinous rice flour, from1.352%to2.572%for glutinous rice starch, and from1.894%to4.987%forindica rice flour, from0.819%to5.878%for indica rice starch.At the same temperature, the solubility of the irradiated rice flour and starch were significantly higher than without the irradiated samples, the irradiation dose the greater the solubility of the greater.The trend of solubility of indica rice flour and glutinous rice flour irradiated was not obvious.After irradiated,the of solubility of indica rice starch and glutinous rice starch were increased with increasing temperature, and the zone of maximal change of solubility of indica rice starch at70℃, increased almost linearly.5X-ray diffraction analysis, the type of glutinous rice flour, glutinous rice starch, indica rice powder and indica rice starch X-ray diffraction patterns was type A. After irradiated,both glutinous rice starch and indica rice starch show a similar of diffraction peaks, distribution was roughly the same.The crystal structure did not change much, but after irradiation the glutinous rice starch and indica rice starch of the diffraction peak intensity and the area of crystal were increased.Glutinous rice flour, degree of crystallinity increased by18.6%, glutinous rice starch crystallinity increased by9.7%,5.1%increase in the crystallinity of indica rice powder, an increase of2.9%in indica rice starch crystallinity.6. The changes of free radicals in rice flour and their starch were analyzed by ESR technology. The results indicated that the contents of free radical were linearly increased with the increment of irradiation doses. Non-radiation samples was almost no signal peak, the peak radiation was increased with the increment of irradiation doses.The content of free radicals also will be increased linearly with increasing radiation dose;The center of magnetic field, the free radicals of glutinous rice flour was higher than that of the indica rice flour, the free radicals of glutinous rice starch was higher than that of indica rice starch. The free radicals in rice flour might come from starch molecules after the overall results were analyzed.