|Hurkman Ii, William|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 21, 2010
Publication Date: November 17, 2010
Citation: Hurkman Ii, W.J., Wood, D.F. 2010. High temperature during grain fill alters the morphology of protein and starch deposits in the starchy endosperm cells of the developing wheat (Triticum aestivum L.) grain. Journal of Agricultural and Food Chemistry. 59(9):4938-4946. DOI: 10.21/jfl102962t. Interpretive Summary: High temperature during grain fill causes variations in wheat flour quality, making commercial production of bread and other baked goods with consistent quality challenging. Although it is known that high temperature causes structural damage to the mature grain, systematic studies on the effect of high temperature on grain structure have not been done. Since flour quality is related to the starch and storage protein reserves stored in endosperm cells of the mature grain, this study focused on investigating the effect of high temperature on the formation of starch granules and protein deposits in the developing wheat grain. Under the high temperature, the large A-type starch granules increased in number, decreased in size, and exhibited pitting; the smaller B-type granules decreased in both number and size; and the protein deposits were greater. Such changes are correlated with variations in dough mixing properties and bread crumb structure. These findings validate the need for wheat varieties that maintain consistent flour quality despite high temperature during grain fill. They also suggest that mechanisms that control the synthesis and size of A- and B-type starch granules and the synthesis and composition of storage protein must be identified to provide breeders with the necessary tools to develop these varieties.
Technical Abstract: High temperature during grain fill reduces wheat yield and alters flour quality. Starchy endosperm cell morphology was investigated in wheat (Triticum aestivum L. ‘Butte 86’) grain produced under a 24/17 °C or 37/28 °C day/night regimen imposed from anthesis to maturity to identify changes in cell structure related to functional properties of flour. The duration of grain fill decreased substantially under the 37/28 °C regimen, but, like the 24/17 °C regimen, endosperm cells in the mature grain were packed with starch and protein. However, A-type starch granules increased in number, decreased in size, and exhibited pitting; B-type granules decreased in both number and size; and the protein matrix was proportionally greater in endosperm cells of grain produced under the 37/28 oC regimen. Such changes in starch granule number, size, and structure and in protein amount are known to contribute to variations in wheat flour quality.