Roller Milling of Canadian Hull-less Barley: Optimization of Roller Milling Conditions and Composition of Mill Streams

Roller milling of hull-less barley generates mill streams with highly variable ß-glucan and arabinoxylan (AX) content. For high ß-glucan cultivars, yields >20% (whole barley basis) of a fiber-rich fraction (FRF) with ß-glucan contents >15% can be readily obtained with a simple short mill flow. Hull-less barley cultivars with high ß-glucan content require higher power consumption during roller milling than normal ß-glucan barley. Recovery of flour from high ß-glucan cultivars was greatly expedited by impact passages after grinding, particularly after reduction roll passages. Pearling before roller milling reduces flour yield and FRF yield on a whole unpearled barley basis, but flour brightness is improved and concentration of ß-glucan in fiber-rich fractions increases. Pearling by-products are rich in AX. Pearling to 15–20% is the best compromise between flour and FRF yield and flour brightness and pearling by-products AX content. Increasing conditioning moisture from 12.5 to 14.5% strongly improved flour brightness with only a moderate loss of flour yield on a whole unpearled barley basis. As moisture content was increased to 16.5%, flour yield declined without a compensating improvement in brightness, but the yield of fiber-rich fraction continued to increase and concentration of ß-glucan in FRF also increased.