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Determining endosperm texture of developing hard and soft red winter wheats dried by different methods using the single-kernel wheat characterization system

1996; Wiley; Volume: 73; Issue: 5 Linguagem: Inglês

Donald B. Bechtel, J. D. Wilson, Charles R. Martin,

Ruminant Nutrition and Digestive Physiology

Cereal Chem. 73(5):567-570 Field-grown hard (Pioneer 2163, Arkan, Karl, Newton, TAM 107, and characterization system was used to measure various grain parameters TAM 200 ) and soft (Caldwell and Clark) red winter wheats were har- including the hardness of individual kernels. Air-dried and oven-dried vested at 15, 18, 21, 23, 25, 28, and 35 days after flowering (DAF). samples generally had similar hardness indices when compared to that of Wheat was dried by a variety of methods: air-dried in the spike at 28 0 C; mature grain. Soft wheats were also softer than hard samples when dried oven-dried in the spike at 40'C; freeze-dried following both freezing and by these two methods. Freeze-dried grain had similar low values of hardthreshing under liquid nitrogen; field-dried mature grain; and freeze- ness for samples harvested between 15 and 28 DAF, but mature 35 DAF thawed and air-dried, in which samples were first frozen in liquid nitro- grains had normal hardness indices. Freeze-thawed samples had hardness gen, thawed at room temperature (23 0 C), and then air-dried in the spike indices slightly higher than those of either air- or oven-dried grain. at 28 0 C. The U.S. Grain Marketing Laboratory's single kernel wheat Grain hardness is an important characteristic that plays a significant role in the marketing and processing of wheat both nationally and internationally. A variety of methods exist for the determination of degree of hardness. However, little is known about the mechanisms of hardness. Generally, hardness is thought to result from the strength of starch-protein interactions (Barlow et al 1973). Softness may possibly be related to the presence of the 15 kDa protein called friabilin isolated from starch of soft wheats (Greenwell and Schofield 1986, Schofield and Greenwell 1987). With the presence of friabilin in endosperm residing on the short arm of the chromosome SD (Jolly et al 1993), friabilin consisting of a family of highly related proteins (Morris et al 1994) and the presence of two classes of starch-bound polar glyco- and phospholipids found in the same pattern as friabilin (Greenblatt et al 1995) suggests that the starch interface must play an important role in determining grain texture in the wheat caryopsis. Little information presently exists as to when endosperm texture (hardness) develops and what effects methods of drying have on hardness. These questions were investigated using the U.S. Grain Marketing Research Laboratory's (USGRL) single kernel characterization system (SKWCS) to measure various grain parameters.