Chemical composition and microstructure of milled barley fractions

Abstract

Wholegrain barley and peeled and pearled barley were roller milled in a Buhler mill, each producing three fractions: endosperm, middlings and bran. These fractions were compared and contrasted with one another and also with milled wheat fractions. Barley endosperm had the highest total starch content in both wholegrain and peeled and pearled barley. Amylose-to-amylopectin ratios (Am:Ap) were higher in barley flours than in wheat flours (P < 0.001). Peeled and pearled barley grain had lower soluble and insoluble fibre contents in all fractions, with wholegrain barley bran in particular having significantly more fibre than that of peeled and pearled barley bran (P < 0.001). The protein contents of the fractions of both barley types did not differ significantly. The endosperm had the lowest protein content, with the bran and middling fractions having double the protein content of the endosperm fraction. The total amino acid concentrations of the fractions followed a similar pattern, the total amino acid concentrations being lower in the endosperm fractions than in the bran and in the middlings fractions. These findings suggest that both types of barley fractions differed essentially from those of wheat. Pearling has a greater effect on the middlings and bran fractions than on the endosperm. The majority of these differences may not be significant enough to impact on the baking qualities of breads made using these fractions.