Effect of extrusion processing on techno-functional properties, textural properties, antioxidant activities, in vitro nutrient digestibility and glycemic index of sorghum–chickpea-based extruded snacks

Physico-chemical, textural, functional, and nutritional properties of the twin screw extruded whole sorghum–chickpea (8:2) snacks was investigated using in vitro procedures. The extruded snacks were analyzed for the effect of variations in extruded conditions on their properties: barrel BT (BT) (130–170°C) and feed moisture (FM) (14%–18%), keeping screw speed constant (400 rpm). The results revealed that specific mechanical energy (SME) decreased (74.4–60.0) in response to rise in both BT and FM, whereas expansion ratio (ER) had shown an alternative relation as it decreased with elevated FM (2.17 at 14%, 130°C to 2.14 at 16%, 130°C) and increased with BT (1.75 at 18%, 130°C to 2.48 at 18%, 170°C). The values of WAI and WSI improved with the surge in BT, which was associated with enhanced disruption of starch granules at higher BT. Raise in FM incremented the total phenolic content (TPC) and hence the antioxidant activity (AA) (FRAP and DPPH) along with the hardness of snacks. As per in vitro starch digestibility is concerned, slowly digestible starch (SDS) content as well as glycemic index (51–53) of the extrudates depressed with increasing BT and FM. Also, lower BT and FM improved the functional properties such as expansion ratio, in-vitro protein digestibility, and overall acceptability of the snacks. A positive correlation was seen among SME and hardness of the snacks, WSI and ER, TPC and AA, SDS and Exp-GI, color and OA, texture and OA.