Development of innovative tigernut-based nutritional snack by extrusion process: effects of die temperature, screw speed, and formulation on physicochemical characteristics

Tigernut (TN) is an underutilized crop with nutritional value that has remained untapped in producing extruded products. This research aims to establish the favorable extrusion conditions that produce a TN-based nutritive extruded snack with improved physicochemical characteristics. A collet extruder was used in this comparison study to examine the effects of formulation (60% TN flour and 40% brown rice [BR] vs. 60% TN flour and 40% Japonica rice [JR]). The effects of extrusion conditions, such as die temperature (90°C, 100°C, and 110°C) and screw speed (250, 300, and 350 rpm), on the physicochemical characteristics of extrudates were studied. TN-BR extrudates produced at 110°C and 350 rpm had the following improved characteristics: protein (6.09–7.33%), ash (1.40–1.59%), crude fat (7.15–9.90%), crude fiber (2.51–3.92%), reduced hardness (2.35–3.37 N), springiness (2.30–2.64), chewiness (234.71–256.72 N), bulk density (1.17–2.57 g/cm3), expansion ratio (1.65–2.24), color (L*: 68.86–74.30), water absorption index (2.69–3.45 g/g), water solubility index (13.95–21.75%), and oil absorption capacity (23.65–25.64 g/g). Extrudates produced at lower temperatures (90°C and 100°C) and screw speed (250 and 300 rpm) exhibited lesser surface consistency than the extrudates produced at 110°C and 350 rpm. The antioxidant activity and the total phenolic content (40.91–49.63 mg gallic acid equivalent/100 g) were improved significantly. Similar improvements were observed in TN-JR extrudates; however, TN-BR extrudates had better nutritional value (higher protein: 7.33%, higher ash: 1.59%, and higher antioxidant activity). The results could help with economic success, food nutrition improvement, and food security by exploiting the underutilized TN crop for sustainable extruded snacks production.