Effects of extrusion cooking on the nutritional quality of puffed snacks made from blends of barley and green lentil flours

Abstract

Increasing demand for nutritionally dense foods warrants the investigation of high fiber and protein ingredients in snack food applications. In this study, blends of barley (22.9% dietary fiber, db) and green lentil (26.4% protein, db) flours were extruded at five blending ratios (barley: green lentil, 100: 0, 75: 25, 60: 40, 45: 55, 0: 100, db), two barrel temperature profiles (60–130 °C and 70–140 °C from feeder to die) and three feed moisture contents (15, 18 and 21%) to produce puffed snacks. Extrusion significantly improved in vitro protein digestibility (IVPD) of all blends by up to 10%. Decreasing feed moisture and increasing die temperature improved IVPD. Blending increased the limiting amino acid score and hence improved the in vitro protein digestibility corrected amino acid score (IVPDCAAS) of extrudates. On average, the blend 45:55 showed the highest average IVPDCAAS (68.62%) among the blends studied and lower glycemic index scores compared to the blend 60: 40. In general, extrusion did not substantially affect the soluble, insoluble or total dietary fiber contents of the blends. All extrudates from blends 60: 40 and 45:55 met the requirement to be labelled as “good source of dietary fiber” in the US.