糯玉米淀粉形成过程中理化特性的变化

为阐明糯玉米淀粉形成过程中理化特性的变化趋势。以6个糯玉米品种为材料,研究了其在花后7 d(淀粉初始期)、22 d(乳熟期)、40 d(成熟期)的淀粉理化特性。结果表明,新形成的淀粉粒为圆型或椭圆型,表层光滑,而鲜食期和成熟期淀粉粒呈不规则的多面体,表层粗糙。淀粉粒径和尖峰强度随生育进程推进逐渐加大(升高)。最大吸收波长和碘结合力以新形成的淀粉粒最高,其次是成熟期。RVA和DSC特征参数在不同生育阶段的变化品种间有显著差异。总体上,随着发育进程推进,淀粉峰值黏度、崩解值、热焓值和回生热焓值先升后降,而回生值、糊化和峰值温度逐渐下降。淀粉形成过程中淀粉粒形态、大小、晶体结构和链长分布发生变化,改变了淀粉糊化和热力学特性。

Physicochemical Properties of Waxy Maize Starch at Early, Middle, and Late Developmental Stages

In order to clarifying the change of waxy maize starch physicochemical characteristics during starch formation, physicochemical properties of waxy maize starch at early form stage (7 DAP), middle milk-ripe stage (22 DAP) and late full-ripe stage (40 DAP) were studied using six varieties as materials. The results indicated that newly formed starch granules are round or oval with smooth surface, whereas starch granules at milk-ripe and full-ripe stages are irregular or polygonal with uneven surface. The starch granule size and peak intensities of starch increase gradually with grain development. The newly formed starch has highest maximum absorption wavelength and iodine-binding capacity, followed by full-ripe starch. The RVA and DSC parameters in response to stages depend on varieties. Generally, the starch peak viscosity, breakdown viscosity, gelatinization and retrogradation enthalpy raise first and fall later, while retrogradation percentage, pasting and peak temperature gradually decrease with the grain development. In conclusion, the change of starch granule morphology and size, crystalline structure and proportion of long chains in amylopectin during grain development induced the change of RVA and DSC parameters.