Effect of Early Harvest and Variety Difference on Grain Yield and Pasting Properties of Brown Rice

Green grains that are harvested before maturity and dehulled have been reported to have higher nutritional value than fully matured brown rice. Two years of aerobic field experiments were conducted to determine the effect of variety, early harvest and their interaction, on grain yield and pasting properties of brown rice. Eight varieties were grown under well-watered or water deficit conditions and harvested between 15-35 days after flowering (DAF). The maximum yield of green rice was obtained when crops were harvested between 20-25 DAF for well-watered condition and 15-20 DAF for water deficit condition. The paddy yield on these early harvest dates was on average 66% of mature paddy rice yield. Varieties were consistent in paddy yield at early harvest 20-25 DAF with correlation coefficient being 0.897 ** between the two years. Rapid visco-analysis (RVA) showed that developing grains had lower pasting viscosities than mature grains. However, the variety difference had a greater effect on pasting viscosities than the harvest time. Varieties were consistent in pasting characteristics between early and mature harvests, and between growing seasons. Water deficit reduced grain yield but did not significantly affect the pasting characteristics of flour gel, amylose and protein content. The RVA showed that final viscosity and setback viscosity in brown rice flour harvested at 15 DAF were only 84% and 76% of those in mature brown rice, indicating that developing grains were likely to produce softer cooked rice than mature grain. The results on differences in pasting characteristics between developing and mature grains provide more options in developing food products with desired gel properties.