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 (Ptemp) increased. The trough viscosity (TV), final viscosity (FV), setback (SB), gelatinization enthalpy (H gel) and retrogradation enthalpy (H ret) decrease first then increased. Percentage of retrogradation (%R), conclusion temperature (Tc), 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 (Tp) was similar between Suyunuo1 and Suyunuo5, and both were higher than Yunuo7. No clear differences were observed on H gel, %R, R and PHI among three varieties. PV was positively correlated to H gel and PHI. BD was negatively correlated to Ptemp and transition temperature (To, Tp, and Tc). 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 H gel, and lower retrogradation tendency.