拔节期追氮对鲜食糯玉米粉糊化和热力学特性的影响

以苏玉糯1号、苏玉糯5号和渝糯7号为材料，研究了拔节期追氮量（N 0、150和300 kg/hm2）对鲜食糯玉米粉糊化和热力学特性的影响。结果表明，随着拔节期追氮量的增加，峰值黏度和崩解值下降，糊化温度升高，而谷值黏度、终值黏度和回复值呈先降后升趋势; 热力学特征参数中，回生值、终值温度、糊化范围和峰值指数受拔节期追氮量影响较小。原样品热焓值和回生后样品热焓值均表现为随着拔节期追氮量的增加呈先降后升趋势。糊化和热力学特征值对拔节期追氮量的响应不同品种间存在差异。鲜食糯玉米粉的理化特性存在显著的基因型差异，峰值黏度以苏玉糯5号最高，苏玉糯1号最低; 峰值温度苏玉糯1号和苏玉糯5号无显著差异，但均高于渝糯7号; 热焓值、回生值、糊化范围和峰值指数不同品种间相对稳定。相关分析表明，峰值黏度与原样品热焓值和峰值指数呈显著正相关; 崩解值与糊化温度及转变温度，回生值与淀粉的终值黏度和回复值呈显著负相关。在本试验条件下，拔节期追氮总体上使糯玉米食用品质降低，其中以苏玉糯5号在不追氮处理下的糊化和热力学特性较优，即峰值黏度、崩解值和热焓值较高，回生值较低。

Effects of nitrogen topdressing at jointing stage on pasting and thermal properties of fresh waxy maize flour

The effects of nitrogen (N) topdressing (N 0, 150 and 300 kg/ha) at jointing stage on flour pasting and thermal properties of fresh waxy maize were studied using 3 varieties (Suyunuo1, Suyunuo5, and Yunuo7) as test materials. With the increment of N topdressing at jointing stage, peak viscosity (PV) and breakdown (BD) decreased, while pasting temperature (P_temp) increased. The trough viscosity (TV), final viscosity (FV), setback (SB), gelatinization enthalpy (ΔH _gel) and retrogradation enthalpy (ΔH _ret) decrease first then increased. Percentage of retrogradation (%R), conclusion temperature (T_c), gelatinization range (R), and peak height index (PHI) were equilibrium among different N topdressing treatments in general. Genotypic differences to N topdressing amount at jointing stage were observed among 3 varieties. The highest PV was found for Suyunuo5, while the lowest was found for Suyunuo1. Peak temperature (T_p) was similar between Suyunuo1 and Suyunuo5, and both were higher than Yunuo7. No clear differences were observed on ΔH _gel, %R, R and PHI among three varieties. PV was positively correlated to ΔH _gel and PHI. BD was negatively correlated to P_temp and transition temperature (T_o, T_p, and T_c). The %R was negatively correlated to FV and SB. Under the experiment condition, N topdressing at jointing stage decreased the eating quality of fresh waxy maize flour. Among the different treatments, the Suyunuo5 presented better pasting and thermal properties under no N topdressing treatment, i.e., the flour possessed higher PV, BD and ΔH _gel, and lower retrogradation tendency.