花后不同强度遮光对糯小麦和非糯小麦淀粉组分和理化特性的影响

花后弱光影响小麦淀粉分子积累和结构形成,进而使面粉的加工品质和食用品质变劣。本研究以非糯小麦轮选987和糯小麦农大糯50206为材料,设置3个花后遮光处理(不遮光、遮光30%和遮光60%),研究了花后不同强度遮光对小麦籽粒中淀粉组分及其理化特性的影响。结果表明,花后弱光胁迫使小麦籽粒中总淀粉含量减少,A-型淀粉粒比例增加,淀粉相对结晶度增大。花后光照强度降低,轮选987淀粉的峰值黏度、谷值黏度、最终黏度、稀澥值和反弹值增大,而农大糯50206淀粉的上述参数则呈减小趋势。轮选987淀粉的起始温度、峰值温度和终止温度随弱光胁迫的增强而降低,而糊化焓呈增加趋势;相反,农大糯50206淀粉的上述热力学特征参数呈降低趋势。相关性分析表明,直链淀粉含量、直/支比、A-型淀粉粒体积比例与相对结晶度、峰值黏度、谷值黏度、稀澥值、糊化时间和糊化焓呈显著负相关,与最终黏度和反弹值存在极显著正相关。可见,小麦花后光照强度降低影响籽粒淀粉组分和粒度分布,从而改变了淀粉的晶体、糊化和热力学特性。

Effects of Post-Flowering Shading Intensities on Starch Components and Physicochemical Properties in Waxy and Non-waxy Wheats

Post-flowering shading may change the accumulation and structure formation of starch in wheat, resulting in deterioration of flour processing and edible qualities. In this study, we observed the changes of starch components and physicochemical properties under 0%, 30%, or 60% shading intensity after flowering in the non-waxy wheat “Lunxuan 987” and the waxy wheat “Nongdanuo 50206”. Under shading stress, the starch content decreased, however, the proportion of A-type starch granules and the relative crystallinity increased in both cultivars. The starch peak viscosity, hold trough, final viscosity, breakdown, and setback in Lunxuan 987 showed increasing trends with the increase of shading intensity; on the contrary, those in Nongdanuo 50206 showed decreasing changes. In Lunxuan 987, stronger shading stress led to decreased onset temperature, peak temperature, and end temperature, but increased gelatinization enthalpy. In Nongdanuo 50206, these starch thermodynamic parameters all decreased with the increase of shading intensity. The correlation analysis showed that amylose content, amylose/amylopectin ratio, and A-type starch granules volume proportion were positively correlated with the relative crystallinity, peak viscosity, hold trough, breakdown, pasting temperature, and gelatinization enthalpy, but negatively correlated with final viscosity and setback. Our findings suggest that post-flowering shading stress has the negative effects on starch components and particle size distribution, thus, resulting in the changes of relative crystallinity, gelatinization, and thermodynamic properties of wheat starch.