关键词: 播期, 糜子, 淀粉, 糊化特性, 晶体结构

Abstract:

【Objective】 The purpose of this study was to analyze the effects of different sowing date on proso millet (Panicum miliaceum L.) agronomic traits and grain starch physiochemical properties, provide theoretical basis for the subsequent study of the mechanism of sowing date on proso millet.【Method】The experiment was carried out in a pot, and Shaanmei No. 1 was used as the test material. Four kinds of sowing dates were set on April 20 (B1), May 10 (B2), May 30 (B3), and June 20 (B4). Different sowing dates, the soil moisture was sufficient during the whole growth period. In 2017, the morphological indexes, grain shape and grain physicochemical properties of the seeds of the proso millet were studied. The plant height, ear length, ear stem length, number of ear branches, 1 000-grain weight, the seeds length, width and roundness of proso millet were analyzed under different sowing dates. In the meantime, the crystal structure, particle size distribution, amylose content, and the enthalpy and gelatinization properties of starch were studied. The correlation of amylose content, enthalpy characteristics and gelatinization properties of starch with morphological index, particle size distribution and particle size parameters were analyzed. 【Result】 The results showed that with the delay of sowing date, the plant height, ear length and ear stem length of proso millet were significantly increased, the main stem tillers and branches were significantly decreased, and the number of secondary spike branches and grain width were significantly decreased. The size distribution of grain starch granules showed a bimodal distribution, and compared with other sowing dates, the particles proportion of B1 had the highest > 28 μm (25.5%) and the lowest 5-28 μm (67.5%) starch granule. The X-ray diffraction pattern showed that changing the sowing date couldn’t affect the crystal type of the proso millet starch, but affected the diffraction peak intensity of the X-ray diffraction pattern. The amylose content (1.3%) of B1 was significantly higher than that in the other sowing dates (0.18%-0.53%). Among the indicators related to the enthalpy characteristics of grain starch in different sowing dates, the gelatinization onset temperature (To), peak temperature (Tp) and conclusion temperature (Tc) showed a tendency of increasing first and then decreasing, while the thermal enthalpy (ΔH) had no significant difference. There were significant differences in the gelatinization properties of proso millet starch under different sowing dates. The peak viscosity (Pv), through viscosity (Tv), final viscosity (Fv) and breakdown (BD) of B3 were significantly higher than the others, while the setback (SB) and peak temperature (PT) were significantly lower than other treatments. With the delay of sowing date, the Pv and BD of proso millet starch increased first and then decreased. B1 starch had the strongest hot paste stability, B3 starch had the strongest cold paste stability and the worst hot paste stability. The cold paste stability of B2 starch was the worst, while the cold paste and hot paste stability of B4 were at an intermediate level. 【Conclusion】 Appropriate sowing date could provide sufficient light and temperature conditions to provide a better environment for the growth of proso millet. Early sowing date significantly increased the 1 000-grain weight of proso millet kernels, the grain was fuller, and the average grain size of grain starch increased, with higher amylose content and nutritional value, which was more suitable for processing hot foods. The sowing date didn’t affect the crystal type of starch, but affected the intensity of the X-ray diffraction peak, the gelatinization characteristics and other indicators of the starch.

Key words: sowing date, Panicum miliaceum L., starch, gelatinization characteristics, crystal structure