不同收获期对两种粳稻综合品质的影响分析

为了探讨收获期对两种粳稻综合品质的影响规律及各品质指标间的相关性,并为优化水稻田间管理和提高稻谷加工产品质量提供基础数据支持,对抽穗后36~66 d的南粳5055和南粳9108分期收割,测定干基千粒质量、外观品质、加工特性、快速黏度分析(rapid viscosity analyzer,RVA)特征谱和蒸煮特性等指标,对数据进行单因素方差分析、相关性分析和主成分分析。结果发现,南粳5055和南粳9108分别在抽穗后48~54 d的干基千粒质量和总淀粉含量显著高于其他时间段(P0.05)。在抽穗后36~66 d内,南粳5055和南粳9108的大米表面明度L~*值先逐渐增大,后期没有显著变化(P0.05),a~*和b~*值则逐渐减小,出糙率和整精米率分别在抽穗后第54天和第48天增长至峰值,后期略有下降。RVA特征谱的峰值黏度和崩解值都呈现"V"字形的变化趋势,两者极显著正相关(P0.01);消减值和糊化温度先增加后降低,回复值和峰值时间随收获期变化不显著(P0.05)。两种粳稻蒸煮硬度分别在抽穗后48~54 d降低至最小值,前者与崩解值呈极显著正相关(P0.01),与消减值呈极显著负相关(P0.01);胶黏性逐渐降低,收获期对其有极显著的影响(P0.01)。基于对品质指标的主成分分析,这两种粳稻的综合品质可由加工特性和营养成分、稻米蒸煮性能和煮熟米饭口感3类重要指标来描述。收获期对两种粳稻整体品质指标影响显著,适时收割会提高稻米的外观色泽和整精米率,改善淀粉糊化特性和米饭蒸煮品质;本次实验条件下南粳5055在抽穗后48~54 d、南粳9108抽穗后54~60 d收割可获得较佳的综合品质。

Effects of Different Harvest Dates on the Overall Quality of Two Japonica Rice Varieties

The aim of this paper is to investigate the effects of harvest date on the overall quality of two japonica rice varieties, and to analyze the relationships among various physicochemical properties for the purpose of providing fundamental data for the optimization of paddy field management and the improvement of rice processing quality. Methods: The cultivars Nanjing 5055 and Nanjing 9108 were harvested at 6-day intervals from 36 to 66 days after heading (DAH). Thousand-grain weight, appearance quality, milling characteristics, rapid viscosity analyzer (RVA) profile and cooking quality of rice grains were measured. Moreover, One-way analysis of variance (ANOVA), correlation analysis, and principal component analysis were conducted on the data obtained. The thousand-grain weights and starch contents of two japonica rice varieties harvested at 48-54 DAH were significantly higher than those harvested at other dates, respectively (P < 0.05). The surface brightness (L*) values of two milled japonica rice varieties gradually increased and then did not change significantly (P > 0.05), and the a* and b* values decreased little by little. Both brown rice rate and head rice rate increased to peak values at 54 DAH for Nanjing 5055 and at 48 DAH for Nanjing 9108, and decreased slightly afterwards. The peak viscosity and breakdown values of rice RVA profiles versus harvest date showed V-shaped curves, and followed a highly significantly positive correlation with each other (P < 0.01) while the opposite trend was observed for setback and pasting temperature. Resilience and peak time did not significantly vary with harvest date (P > 0.05). For the two varieties, the hardness value of cooked rice decreased to the minimum values at 48-54 DAH, which was highly significantly positively correlated with breakdown (P < 0.01), and highly significantly negatively correlated with setback (P < 0.01). Gumminess gradually decreased, which was highly significantly influenced by harvest date (P < 0.01). Principal component analysis showed that the overall quality of these rice varieties could be described by processing quality and nutritional contents, rice cooking performance and cooked rice palatability. The quality of the japonica rice varieties was greatly influenced by harvest date. The suitable harvest time could not only increase the appearance quality and head rice rate, but also improve the starch gelatinization properties and cooking quality of japonica rice. Under the experimental conditions of this study, the optimal harvest time was 48-54 DAH for Nanjing 5055, and 54-60 DAH for Nanjing 9108.