Abstract:

【Objective】 The objective of the study is to understand the effects of sowing date, variety and nitrogen (N) top-dressing at jointing stage on waxy maize starch granule size distribution and clarify the relations between granule size distribution and pasting and thermal properties. 【Method】The effects of N top-dressing (0, 150 and 300 kg?ha-1) at jointing stage on waxy maize starch granule size distribution were studied under spring and autumn treatments using national regional test control varieties (Kennian 1, Suyunuo 1 and Suyunuo 5) as materials.【Result】Starch granule size distribution was significantly affected by the single factor and interactions of sowing dates, varieties and N top-dressing amount at jointing stage, and the variation coefficients from sowing dates were larger than varieties and N topdressing treatments. In general, the average diameter and the proportion of diameter higher than 17 μm were lower under autumn sowing treatment. Among the 3 varieties, the average diameter was the lowest for Suyunuo 1 and the highest for Suyunuo 5, the proportion of diameter higher than 17 μm was lowest for Suyunuo 1 and similar between Kennian 1 and Suyunuo 5. With the increment of N top-dressing at jointing stage, the average diameter and the proportion of diameter higher than 17 μm rose first and fell later, whereas the proportion of diameter between 13 and 17 μm fell first and rose later. The average diameter and the proportion of diameter higher than 17 μm were negatively correlated to peak viscosity and breakdown, whereas it was positively correlated to pasting temperature, onset temperature, and peak temperature. The proportion of diameter between 9 μm and 17 μm was positively correlated to peak viscosity and breakdown, whereas it was negatively correlated to pasting temperature, onset temperature, and peak temperature. No significant correlations were observed between starch granule size distribution and setback, enthalpy of gelatinization and the percentage of retrogradation. 【Conclusion】 It was concluded that the sowing date was the key factor that change the granule size distribution. In the autumn sowing treatment, using Kennian 1 as material and topdressing 150 kg?ha-1 N at jointing stage, the starch presented higher proportion of diameter between 9 and 17 μm, lower average diameter and the proportion of diameter higher than 17 μm, which results in better pasting and thermal properties.

Key words: waxy maize starch, granule size distribution, sown dates, nitrogen topdressing at jointing stage, variety