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Cereal Chem. 71:369-383   |  VIEW ARTICLE

Effects of Temperature During Grain-Filling on Starches from Six Wheat Cultivars.

Y.-C. Shi, P. A. Seib, and J. E. Bernardin. Copyright 1994 by the American Association of Cereal Chemists, Inc. 

Six wheat cultivars were placed in growth chambers during the grain-filling period and were subjected to maximum daylight temperatures of 15, 25, or 40 C daily for 5 hr. The same wheats also were grown in the greenhouse at a mean temperature of 18 C. In addition to causing shriveled kernels and low test weight, elevated temperature reduced starch accumulation and size of starch granules, and resulted in deformed starch granules, especially in hard and durum wheats grown at 40 C. With increasing temperature during grain-filling, starch lipid levels were increased markedly, amylose level was increased slightly, gelatinization temperatures of the starches increased, and swelling of the starches in hot water decreased. Annealing the starches for 48 hr at 6 C below the onset temperature (To) of gelatinization increased the To values, but the differences in To values among the starches remained. Starches from most wheats grown at 40 C had increased proportions of unit chains with degrees of polymerization (DP) of 10-16 and reduced proportions of unit chains with DP 17-21. Starches from wheats grown at 25 C had the highest proportions of unit chains with DP 16-24, which appeared to explain the increased extent of retrogradation.

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