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Abstract: The effects of high temperature during different grain filling stages (1–15d and 16–30d after pollination) on the physicochemical properties of four varieties of waxy maize grain were studied. Heat stress during grain filling decreased grain weight and starch deposition, while it increased protein content, starch granule size, abnormal granule numbers and iodine binding capacity. These effects were more severe when heat stress was introduced at early development stage than at late grain filling stage. The peak intensities and crystallinities were decreased when plants were exposed to high temperature at early development stage. By contrast, responses to high temperature at late development stage were variety-dependent. High temperature during grain filling decreased the peak and breakdown viscosities and increased the gelatinization temperature and enthalpy, and retrogradation percentage of flours, especially during early development stage. In conclusion, high temperature during grain filling changed the grain proximate and starch structure, resulting in the deterioration of pasting and thermal properties. [Copyright &y& Elsevier]

• Waterlogging decreased starch granule size. • Waterlogging increased the proportion of long-chains and high-molecular-weight molecules in amylopectin. • Ordered structure of waterlogged starch decreased peak and breakdown viscosities. The grain formation stage is a critical stage that affects grain starch quality and frequently overlaps the rainy season in southern China for waxy maize production. Two waxy maize varieties were grown under control and waterlogging conditions during grain formation (1–15 days after pollination) to probe the effects of oversaturated soil moisture on starch structural and functional characteristics. Results indicated that waterlogging during grain formation decreased the size of starch granule, proportion of large granule (d > 15 μm) and ratio of medium-length chains (DP 10–24) in amylopectin, whereas the percentage of high-molecular-weight molecules were increased. Compared with the control, the percentage of ordered starch was increased by waterlogging for both varieties. The changes in starch internal structure under waterlogging had no influence on thermal stability, increased the maximum thermal decomposition ratio and pasting temperatures, and reduced pasting viscosity characteristics in both varieties. [ABSTRACT FROM AUTHOR]