Distribution of β-glucan in the grain of hull-less barley

Nine hull-less barley (HB) containing waxy (0-7% amylose), normal (approximate to 25g amylose), or high amylose (approximate to 42% amylose) starch with normal or fractured granule make-up and 4-9% (1-->3)( 1-->4)-beta-D-glucans (beta-glucan) were pearled to remove 70% of the original grain weight in 10% intervals. The pearled fractions were analyzed for beta-glucan distribution within HB grain. Protein content of the pearled fractions indicated that the three outermost fractions contained pericarp and testa, aleurone, and subaleurone tissues, respectively For all HB, beta-glucan and acid-extract viscosity were very low in the outermost 20% of the kernel. For low beta-glucan HB, beta-glucan content was the greatest in the subaleurone region and declined slightly toward inner layers. For high beta-glucan HB, however, more than 80% of grain beta-glucan was distributed more evenly throughout the endosperm. Acid extract viscosity was significantly (P < 0.01) correlated with total (r = 0.75) and soluble (r = 0.87) beta-glucan content throughout the kernel of all HB. Growing conditions, location and year, had significant effects on the concentration of protein, starch and beta-glucan. However, protein, starch, and beta-glucan distribution patterns were not affected by growing conditions. The difference in beta-glucan distribution between low and high beta-glucan HB may explain the difference in milling performance of HB with low or high beta-glucan.