Rice grain protein composition influences instrumental measures of rice cooking and eating quality

Rice cultivar starch composition differences do not completely explain variation in rice cooking and eating quality. Rice grain storage proteins possess divergent solubility properties suggesting they may contribute to cultivar differences in rice grain quality. Application of high-performance liquid chromatography (HPLC) analysis to protein extracts derived from medium and long grain advanced rice breeding lines revealed rice grain protein composition differences which were associated with instrumental measures of grain quality. Globulin content displayed little variation in both grain types. The mean glutelin content was higher in long grain rice lines than medium grains. Although the mean content of prolamins in medium and long grain rice were similar, the prolamin content of medium grains was more variable. Individual medium grain prolamin HPLC peaks, total prolamin content and the prolamin:glutelin + prolamin ratio were positively correlated with several rapid visco analyser (RVA) parameters. The long grain HPLC data displayed a similar pattern of correlations with RVA parameters but of reduced magnitude. Protein composition was associated with instrumental measures of grain quality in this set of germplasm and although the textural properties of rice are complex, these data suggest consideration of rice grain protein composition could contribute to breeding high quality rice.