Abstract

Background and objectives Movement of moisture into dry grain can cause the grain to take on a weathered, bleached appearance. Bleaching is a concern for durum producers since the grain price is often discounted. A series of experiments were conducted to determine the effect of grain moisture content, temperature, and wet/dry cycles with bulk water and with high relative humidity on the hydration of durum wheat (Triticum turgidumL. ssp.durum[Desf.] Husn.) grain and their effect on physical grain quality parameters related to bleaching. Findings Water gain was greater for grain with low (13%) than high (17%) initial moisture content, which resulted in similar grain moisture contents (similar to 30%) after 3 hr of soaking. At 24 degrees C, there was more water uptake than at 5 degrees C. Exposure to a single bulk water wet/dry cycle caused durum kernels to increase in width and caused a rough and wrinkled bran surface which resulted in a decline in test weight and vitreous kernel content and an increase in kernel size and brightness. A single high relative humidity event caused a reduction in vitreous kernel content and an increase in kernel size. Additional cycles of high relative humidity were needed to cause a reduction in test weight. Micrographs from scanning electron microscope and light microscope showed that the germ and ventral surface of grain were important sites for water absorption. Conclusions Initial grain moisture, temperature, and wet/dry cycles affected water gain. A single exposure to moisture (bulk water or high relative humidity) was enough to cause a decline in physical grain quality. Significant and novelty These data confirm anecdotal stories from durum producers that a single moisture event can cause bleaching and reduce grain quality and value.