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Abstract: BACKGROUND: Waxy maize (Zea mays L. sinensis Kulesh) suffers short‐term exposure to high temperature during grain filling in southern China. The effects of such exposure are poorly understood. RESULTS: Starch granule size was increased by 5 days' short‐term heat stress (35.0 °C) and the increase was higher when the stress was introduced early. Heat stress increased the iodine binding capacity of starches and no difference was observed among the three stages. Starch relative crystallinity was increased and swelling power was decreased only when heat stress was introduced early. Heat stress also increased the pasting viscosity, and this effect became more pronounced with later applications of stress. Heat stress reduced starch gelatinization enthalpy, and the reduction gradually increased with later exposures. Heat stress increased the gelatinization temperature and retrogradation enthalpy and percentage of the samples, with the increases being largest with earlier introduction of high temperature. CONCLUSION: Heat stress increased the pasting viscosities and retrogradation percentage of starch by causing change in granule size, amylopectin chain length distribution and crystallinity, and the effects observed were more severe with earlier introduction of heat stress after pollination. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Highlights: [•] Heat stress increased starch granule size and made their surface more uneven or pitting. [•] Heat stress decreased the swell power of waxy maize starch. [•] X-ray diffraction peak intensities in response to heat stress were variety dependent. [•] Heat stress did not affect the gelatinization enthalpy. [•] Heat stress increased the gelatinisation temperature and retrogradation tendency. [ABSTRACT FROM AUTHOR]

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]