19 Beta-glucan distribution in hull-less barley: A pearling study.

G. H. ZHENG (1) and B. G. Rossnagel (2). (1) Department of Applied Microbiology and Food Science and (2) Crop Development Centre, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada.

Nine genotypes of hull-less barley (HB), grown in 3 locations and 2 years, containing waxy, high amylose, regular or fractured starch granules and different levels of beta-glucan were studied for quantitative distribution of beta-glucan within the grain. Pearled fractions were successively collected by pearling HB to 90, 80, 70, 60, 50, 40 and 30% of original kernel weight using Satake Experimental Mill. Crude protein, total beta-glucan, acid-extract viscosity and acid-soluble beta-glucan content of the fractions were determined. Protein distribution and visual observation indicated that pearling evenly removed all surfaces of HB with little breakage, resulting in fractions consisting of various morphological components of the grain. Beta-glucan content was very low in the outermost 10% (pericarp and testa) of the grain irrespective of genotype, growing location and year. Compared with the outermost fraction, average beta- glucan content increased more than 2-fold in aleurone fractions. For low beta-glucan HB, beta-glucan was the highest in the sub-aleurone fractions then decreased toward the central core. For high beta-glucan HB, beta-glucan was higher in endosperm than sub-aleurone and distributed more uniformly throughout the endosperm of the grain. Acid-extract viscosity was highly correlated with total and acid-soluble beta-glucan content throughout HB kernels. The effect of growing season and location on beta-glucan distribution is discussed.