Physical and microstructural quality of extruded snacks made from blends of barley and green lentil flours

Background and objectives: Most puffed snacks in the market are made from refined cereal flours which allow greater expansion and better texture but are nutritionally inferior as they lack protein and dietary fiber. Whole barley and green lentil flours at several blending ratios were extruded as a function of temperature and moisture content to optimize the physical and microstructural quality of fiber and protein-enriched snacks. Findings: High extrusion temperature significantly improved overall expansion and texture. The effects of feed moisture depended on the blending ratio, parallel with the total protein and dietary fiber content of extrudates. Barley:green lentil of 45:55 showed the highest extrudate expansion (similar to 1.9 mm/mm on average) and lowest hardness (similar to 29 N on average), followed by the blend 60:40. X-ray microtomography showed that this blending ratio also produced a larger mean cell size (similar to 1.6 mm), lower mean wall thickness (similar to 0.3 mm), and higher overall connectivity between cells. Conclusion: Barley and green lentil when blended at the ratios of 45:55 and 60:40, and extruded at higher temperature resulted in optimal extrudate physical and microstructural properties including higher expansion and crispness, thinner cell walls, reduced hardness, and crunchiness. Significance and novelty: Blending cereal and pulse flours in snack food applications will allow development of fiber and protein-enriched options that are also texturally and structurally appealing.