Liu Qiaoquan

Milling Characteristics and Distribution of Seed Storage Proteins in Rice with Various Grain Shapes

Rice(Oryza sativa L.),one of the most important crops,is a very good and relatively cheap source of energy and protein.The processing quality and nutrition distribution are different among rice varieties.The objective of the present study was to explore the distribution of proteins in rice kernel and to provide some references on the processing of high-quality rice using three rice cultivars with different quality and grain shapes,including two japonica cultivars Suyunuo and Yangfujing 4901,and one indica rice Qiangluzhan 11.The degree of milling(DOM,0–25%) and milling time were carefully measured,respectively.The results showed that the hardness was increased from outer to inner bran layers,and unchanged in endosperm fractions,which was higher than that of bran layers.This non-linear relationship between milling time and DOM implied variability in hardness within different rice fractions.Furthermore,the analysis of relationship between protein content and DOM indicated that the protein was not equably distributed within the brown rice kernel.The endosperm(DOM 9%) was identified to contain most of the rice kernel proteins(about 85% of total seed proteins) in all the three cultivars.But the protein content in the brown rice kernel decreased from outer to inner fractions,and that in core endosperm fractions was only about half of that in bran layers.In addition,SDS-PAGE analysis for total proteins in the grains with various DOM showed that the distribution of seed protein components was relatively uniform,suggesting the synchro genetic expression of seed protein components in rice grain.