新采收玉米籽粒中水分状态对淀粉热特性的影响

摘要

This study aimed to verify the impact of moisture distribution status on thermal characteristics of starch from newly harvested maize. Two maize cultivars in northeast China, Zhengdan 958 and Xianyu 335, were used in this study. Low field nuclear magnetic resonance (LF-NMR) and differential scanning calorimeter (DSC) were applied to study changes in water migration and distribution status in maize kernels during 60 days of postharvest storage and changes in thermal characteristics of maize starch were also examined. The results showed that the relaxation time (T2) and water distribution changed significantly (P < 0.05) during the postharvest storage period. For both cultivars, the melting enthalpy of maize starch gels reached a maximum value of 18.54 and 15.06 J/g at 40 d after harvest, respectively. There was a significantly negative correlation between the relative area (A21) and the relaxation time (T21) of bound water and moisture content of maize grains (P < 0.01). In addition, A21was significantly correlated with endothermic enthalpy (ΔH) of starch gels (P < 0.05). Accordingly, changes in the crystal structure of starch may be partly related to water migration and distribution status. LF-NMR can effectively analyze the dynamic changes of moisture during the postharvest storage of maize and its effect on the functional properties of starch.%以2 种中国东北地区玉米郑单958(Zd958)和先玉335(Xy335)为研究对象,采用低场强核磁共振技术(low field nuclear magnetic resonance,LF-NMR)和差示扫描量热技术分析新玉米采后60 d内籽粒水分迁移和分布变化,及其对淀粉热特性影响.结果表明,东北新采收玉米采后水分T2弛豫时间和水分分布呈显著变化(P＜0.05),2 种玉米淀粉凝胶焓值在40 d达到最高分别为18.54 J/g和15.06 J/g,结合水弛豫时间T21与籽粒水分含量呈极显著相关(P＜0.01),结合水相对面积A21与籽粒水分含量呈极显著负相关(P＜0.01),A21与凝胶吸热焓值(?H)呈显著相关(P＜0.05),表明水分迁移和分布是影响淀粉分子晶体结构变化原因之一,利用LF-NMR技术可以有效分析采后籽粒内部水分动态变化,及其对淀粉功能特性影响.