Influence of Preharvest Sprouting on Rice Quality of Medium Indica Rice in Sichuan Basin
[Objective]The specific objective of this study was to clarify the effects of preharvest sprout-ing on rice grain quality and to provide guidance for the production of high-quality rice in Sichuan Basin.[Method]Using Guichao II and Xikehui 768 as experimental materials,we collected both germinated and ungerminated grains in the field at the maturity stage and analyzed the effects of preharvest sprouting on the milling and appearance qualities,composition,and starch RVA profile of the rice.[Result]In terms of processing appearance quality,preharvest sprouting led to significant reductions of 4.44％,7.48％,and 3.83％,and 13.88％,8.90％,and 34.94％in the brown rice rate,milled rice rate,and head rice rate for Xikehui 768 and Guichao Ⅱ,respectively.Preharvest sprouting also led to a reduction in the grain weight of head rice by 10.99％for Xikehui 768 and 3.57％for Guichao Ⅱ,respectively.It resulted in a significant increase in the chalky grain rate and chalkiness degree by 23.71％and 22.6％for Xikehui 768,and by 23.19％and 9.98％for Guichao Ⅱ,respectively.Compared with ungerminated grains,preharvest sprouting significantly decreased the protein and fat content by 0.9％and 1.43％in Xikehui 768,and by 0.35％and 0.33％in Guichao Ⅱ,respectively.Moreover,preharvest sprouting significantly reduced the peak viscosity,hot paste viscosity,and cool paste viscosity of Xikehui 768 and Guichao Ⅱ by 82.72％,96.68％,and 95.66％,and by 56.55％,72.63％,and 57.66％,respectively.This re-sulted in a 127.71％and 95.27％reduction for Xikehui 768 and a 61.18％and 31.83％reduc-tion for Guichao Ⅱ in setback viscosity and consistency viscosity,respectively.The results of the correlation analysis showed that the starch RVA spectral properties were closely related to the processing appearance quality and rice fractions.Peak viscosity,hot paste viscosity,and cool paste viscosity were significantly an positively related to the brown rice rate(r=0.752,0.805,and 0.695),milled rice rate(r=0.853,0.904,and 0.801),head rice rate(r=0.651,0.752,and 0.584),grain weight of head rice(r=0.696,0.731,0.709),protein content(r=0.708,0.626,0.728),and fat content(r=0.915,0.861,0.946),but significantly and negatively associated with chalky grain rate(r=-0.966,-0.963,-0.945)and chalkiness degree(r=-0.812,-0.834,-0.819).[Conclusion]In sum-mary,preharvest sprouting seriously decreased the milling,appearance,and cooking and eating quali-ties of medium indica rice in the Sichuan Basin,and the influence of preharvest sprouting on rice quality depends on the rice varieties.
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