鲜食期和成熟期糯玉米粉理化特性的差异

以5个糯玉米品种为材料，研究其鲜食期和成熟期籽粒的理化特性。结果表明，糯玉米粉的最大吸收波长鲜食期和成熟期无显著差异，均表现出典型的糯性特征，禾盛糯1512成熟期的蓝值高于鲜食期，其余品种鲜食期和成熟期无显著差异。成熟期糯玉米粉具有较高的淀粉含量和较低的蛋白质含量。成熟期糯玉米粉的结晶度和膨胀势高于鲜食期，而溶解度和透光率低于鲜食期，但不同品种对收获期的响应不一致。中糯319鲜食期的黏度特性较优，其他4个品种成熟期较优，鲜食期收获的粤彩糯1号不能糊化。差示扫描量热仪结果表明，成熟期收获的糯玉米粉具有较低的转变温度(起始温度、峰值温度、终值温度)、热焓值、峰值指数以及较宽的糊化范围，鲜食期收获的糯玉米粉具有较低的回生值。相关分析表明，最大吸收波长与峰值黏度显著正相关(相关系数为0.63，P<0.05)，与糊化温度显著负相关(相关系数为-0.86，P<0.01)。结晶度与糊化温度显著负相关(相关系数为-0.70，P<0.05)，与热焓值、峰值指数及回生后的热焓值显著正相关(相关系数分别为0.74，P<0.01；0.62，P<0.05；0.74，P<0.01)。回生值与蓝值、最大吸收波长、结晶度及回生后的热焓值显著正相关(相关系数分别为0.64，P<0.05；0.61，P<0.05；0.69，P<0.05；0.96，P<0.01)。中糯319鲜食期收获具有较高的淀粉含量、结晶度和黏度特征值，适宜作鲜食；粤彩糯1号两个时期的回生值远低于其他品种，适宜制作低回生的食品。

Differences of Physicochemical Properties for Waxy Maize Flour at Fresh and Maturity Stages

Understanding the differences of physicochemical properties of flours from different waxy maize cultivars at fresh and maturity stages could make its utilization proper. In the study, the flour physicochemical properties of five waxy maize cultivars at fresh and maturity stages were measured. The results indicated that the λ_max was similar at two stages and presented typical waxy character. Heshengnuo 1512 harvested at maturity presented higher blue value (BV), whereas the other four cultivars had similar BV at two harvest stages. The flour presented higher starch content and lower protein content when the maize was harvested at maturity. The crystallinity and swell power at maturity were higher than those at fresh, whereas the solubility and light transmittance were lower at maturity, and the responses of the physicochemical characteristics to harvest stage were different for different cultivars. Zhongnuo 319 harvested at fresh presented higher viscosity characteristics and lower pasting temperature, whereas the viscosity properties for the other four cultivars were better at maturity, and Yuecainuo1 could not paste at fresh. Differential scanning calorimetry (DSC) results demonstrated that flour at maturity had lower transition temperature (onset, peak, and conclusion temperature), enthalpy of gelatinization (DH_gel), peak height index (PHI) and wider gelatinization range (R), whereas the percentage of retrogradation (%R) was lower at fresh. Λmax was positively correlated to peak viscosity (r=0.63, P<0.05), and negatively correlated to pasting temperature (r= -0.86, P<0.01). Crystallinity was negatively correlated to pasting temperature (r = -0.70, P<0.05), and positively correlated to DH_gel (r=0.74, P<0.01), PHI (r=0.62, P<0.05) and enthalpy of retrogradation (DH_ret) (r=0.74, P<0.01). %R was positively correlated to BV (r=0.64, P<0.05), λ_max (r=0.61, P<0.05), crystallinity (r=0.69, P<0.05), and DH_ret (r=0.96, P<0.01). Among the five cultivars, Zhongnuo 319 harvested at fresh presented higher starch content, crystallinity, and viscosity characteristics, which makes it better in fresh eating quality. Yuecainuo 1 at both harvest stages had the lowest %R among the cultivars, indicating its advantage using for the food that needs lower retrogradation.