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Distribution of β-Glucan in the Grain of Hull-less Barley

¹Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8. ²Corresponding author. Phone: 937/237-2573. Fax: 937/237-2529. E-mail: tedzheng@cargill.com Current address: Cargill, Inc., 3201 Needmore Rd., Dayton, OH 45414. ³Crop Development Centre, Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8.

Nine hull-less barley (HB) containing waxy (0–7% amylose), normal (≈25% amylose), or high amylose (≈42% amylose) starch with normal or fractured granule make-up and 4–9% (1→3)(1→4)-β-D-glucans (β-glucan) were pearled to remove 70% of the original grain weight in 10% intervals. The pearled fractions were analyzed for β-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, β-glucan and acid-extract viscosity were very low in the outermost 20% of the kernel. For low β-glucan HB, β-glucan content was the greatest in the subaleurone region and declined slightly toward inner layers. For high β-glucan HB, however, more than 80% of grain β-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) β-glucan content throughout the kernel of all HB. Growing conditions, location and year, had significant effects on the concentration of protein, starch and β-glucan. However, protein, starch, and β-glucan distribution patterns were not affected by growing conditions. The difference in β-glucan distribution between low and high β-glucan HB may explain the difference in milling performance of HB with low or high β-glucan.