Air classification of barley flours

Flour samples from seven different barleys, including covered and naked barleys and barleys with normal, waxy, and high-amylose starches, as well, as the high-fiber barley Prowashonupana, were impact-milled and air-classified in a pilot unit. Six fractions (F1-F5 and C5) with increasing particle size were obtained from each barley All fractions were analyzed for ash, protein, starch, dietary fiber, and total and unextractable beta-glucan. Ash was enriched in C5; covered barleys (4.3-5.7% of dry matter) had a higher ash content than naked barleys (2.1-3.2%). Starch was enriched in F4 for normal and waxy barleys (72-79%) and in F3 for high-amylose barleys (72-75%). Protein was enriched in F1 (14-26%) for the different barleys. beta-glucan was enriched in F5 and C5 (7-23%), Prowashonupana had the highest value. The extractability of beta-glucan decreased with increasing particle size, probably because of lower amounts of endogenous beta-glucanase and poorer availability of the substrate in larger particles.