Studies On The Dynamic Changes Of Rice Pigment And Grain Quality Formation

Rice is one of the most important crops in the world. About 65% people all over the world take the rice as their most important food. So the hygienical capability, as well as the quantity of the rice makes a direct effect on people's demands of food and their satisfaction. It also effects on human's healthy, and the development of the food processing industry. With the development of the living standard, people pay more attention to the quality and efficacy of rice.In our research, according to the complex climate in Changsha, we study the relationship between rice pigment, grain filling and grain quality in three seasons, in order to find out the optimal harvest period. The materials of the experiments: XiangZaoXian24, XiangZaoXian143, ZiXuan1 and ZiXuan2(red rice). The main conclusions are as follows:1. It decided the optimal harvest period to the high temperature duration during the grain filling stage. The longer high temperature duration, the earlier the best harvest time. The grain filling suitable harvest period is from 15 to 25 day after heading in the early season, from 20 to 25 day after heading in the middle season and 25 day after heading in the late season.2. Through the research on the changes of chlorophyll and carotenoids contents of hull and ovary of grain, we can make an indication that the change trend is the same at the pigment contents in the ovary and hull of grain, but the ovary's get behind the hull of grain's a little. The optimal harvest period of rice pigment is from 20 to 25 day after heading in three seasons.3. We research four rice quality traits—head milled rice rate, chalkiness degree, amylase content and alkali value, the result showed that high temperature (35℃)at the filling stage can lead to lower head milled rice rate and amylase content and higher alkali value and chalkiness degree. Endosperm of grain structure of X-ray diffraction analysis shows that amylase increased during grain filling stage, relative crystallinity is a "V"-type curve in early and middle season and a single peak curve in late season, it is the best harvest time when rice starch in the crystal structure of 2θto 20°around the diffraction peak appear , which is 25 day after heading in the early and late season and from 20 to 25 day after heading in the middle season.4. The mean daily temperature was the most important climate factor to head milled rice rate, chalkiness degree and alkali value, the mean highest temperature was the most important climate factor to amylase content and relative crystallinity.5. In conclusion, the optical harvest period was 25 day after heading in the early season, 20 day after heading in the middle season and 25 day after heading in the late season.