灌浆结实期水分胁迫对糯玉米粉理化特性的影响

Effects of Water Stress During Grain Filling on Physicochemical Properties of Waxy Maize Flour

【目的】明确灌浆结实期水分胁迫对糯玉米粉理化特性的影响。【方法】以苏玉糯5号和渝糯7号为材料,利用负水头供水控水盆栽装置研究灌浆结实期水分胁迫(土壤相对含水量为90%、75%和60%,分别代表水分过量、正常和亏缺)对糯玉米粉理化特性的影响。【结果】糯玉米粉糊化特征值中,谷值黏度、终值黏度、回复值和糊化温度受水分胁迫影响较小,水分亏缺使峰值黏度和崩解值降低。差示扫描量热仪(DSC)研究表明,热焓值和终值温度受水分胁迫影响较小,起始温度和峰值温度在水分亏缺时较高,且水分过量或亏缺均导致样品回生值增加。苏玉糯5号籽粒淀粉平均粒径和直径>17μm淀粉粒比例在土壤水分正常时较低,而渝糯7号恰好相反。最大吸收波长在水分正常时最低,水分亏缺时最高。碘结合力和结晶度苏玉糯5号受土壤含水量影响较小,渝糯7号在土壤水分亏缺时碘结合力较高而结晶度较低。【结论】灌浆结实期土壤水分胁迫对糯玉米粉糊化和热力学特性有显著影响,水分亏缺时较低的结晶度和较高的碘结合力导致糯玉米粉峰值黏度和崩解值较低,起始温度、峰值温度和回生值较高。水分正常时,籽粒加工品质较优(高峰值黏度与崩解值,低回生值)。

[ Objective ] Understanding the effects of water stress during grain filling on physicochemical properties of waxy maize flour. [Method] A negative pressure water supplying and controlling pot device was used to control different soil moisture contents （SMC） by setting the water supply tension of the device at different values. The effects of water stress （relative SMC was 90%, 75%, and 60%, indicated the water supply was excessive, moderate, and deficient, respectively） during grain filling on physicochemical properties of waxy maize flour were studied using Suyunuo5 and Yunuo7 as test materials. [Result] Among different pasting characteristics, trough viscosity, final viscosity, setback and pasting temperature were not affected by water status, while the lower peak viscosity and breakdown were presented when SMC was deficient. The results of differential scanning calorimetry observed that enthalpy of gelatinization and conclusion temperature were similar among different water treatments; onset and peak temperature was higher at deficient water supply treatments. Compared with moderate SMC, both excessive and deficient SMC increased the percentage of retrogradation. The average granule diameter and percentage of starch granule size that diameter 〉 17 ~rn were the lowest when SMC was moderate for Suytmuo5, while it was the highest for Yunuo7. Amax was the lowest when SMC was moderate and it was the highest when SMC was deficient for both varieties. Iodine binding capacity and crystallinity were stable among different SMCs for Suyunuo5, while the higher iodine binding capacity and lower crystallinity were presented when SMC was deficient for Yunuo7. [Conclusion] The lowest crystallinity and highest iodine binding capacity at deficient SMC treatments resulted in the lowest peak viscosity and breakdown, and highest onset temperature, peak temperature and percentage of retrogradation. The waxy maize flour presented better processing quality （higher peak viscosity and breakdown, low percentage of retrogradation） at moderate SMC treatments.