Milling and extrusion of six barley varieties, effects on dietary fibre and starch content and composition

Barley is a rich source of dietary fibre that can promote beneficial physiological effects. The carbohydrate composition in different barley varieties differs considerably and choice of variety is thus important. This study examined whether differences in carbohydrate composition observed in barley kernels of different varieties persisted in the sifted flour and in an extruded product. Six barley varieties were milled and extruded and dietary fibre and starch in the kernels, flour and extruded product were analysed. The starch content was found to be higher in flour and extruded product than in kernels. The content of arabinoxylan was higher in sifted flour than in kernels, but was decreased by extrusion. The extractability of arabinoxylan was increased by extrusion, while its average molecular weight was decreased. Extrusion also decreased the content of mixed-linkage (1 → 3),(1 → 4)-β-D-glucan in all varieties, but increased its extractability. The six barley varieties were affected in much the same way by milling and extrusion, but clear differences could still be observed. For example, the arabinoxylan in variety SW 28708 was less affected and variety KVL 301 had much lower extractability (76% vs 91–98%) of mixed-linkage (1 → 3),(1 → 4)-β-D-glucan after extrusion than the other varieties.