Hulled varieties of Barley showed better expansion characteristics compared to hull-less varieties during twin-screw extrusion

Background and objectives Consumption of food barley is increasing due to its health and nutritional benefits. Whole grain flours of two hulled barley varieties, Lyon and Muir, and three hull-less barley varieties, Havener, 09WA-265.12, and Meg's Song, were extruded with a co-rotating twin-screw extruder. The impacts of feed moisture, screw speed, and die temperature on functional properties of extrudates were investigated. Findings Expansion ratio (ER) of barleys was slightly lower compared to the reported numbers for cereals such as corn. Hulled varieties showed significantly higher ER compared to the hull-less varieties. Havener was the only hull-less variety having comparable ER with hulled varieties and moderate levels of ss-glucan. ER correlated positively with water solubility index (r = 0.680, p < 0.01), specific mechanical energy (r = 0.633, p < 0.01), and negatively with unit density (r = -0.729, p < 0.01). Conclusions Hulled varieties are better suited for extrusion expansion. Feed moisture and die temperature had a strong influence on expansion, while screw speed showed marginal effects. Significance and novelty: Understanding the properties of hulled and hull-less barley extrudates will enable process industry to utilize them for the development of novel extruded foods, while taking advantage of their nutritional values.