Effect of extrusion parameters on physical, microstructural and functional quality of lentil-quinoa extruded snack enriched with pumpkin by stepwise response surface methodology

Abstract

This study aimed to develop lentil-quinoa-pumpkin extruded snacks by investigating the effects of extrusion conditions (pumpkin flour ratio (A: 25–75%); barrel screw speed (B: 120–180 rpm) and feed moisture content (C: 14–22%) on water-activity (aw), Water Absorption Index (WAI: g.g-1), Water Solubility Index (WSI%), Oil Absorption Index (OAI: mL.g-1); expansion ratio (ER), Bulk-density (BD: g.cm-3), porosity (%) and hardness (N). Box-Behnken experimental design and Stepwise-response surface method were applied to analysis and model the properties of the extruded snacks. The pumpkin-flour ratio had a significant positive correlation with BD, OAI and WSI. Whereas the correlation between this parameter and hardness, porosity, ER and WAI was negative (P < 0.05). The feed moisture content was positively affected the aw and WAI and negatively affected the harness of samples (P < 0.05). The screw speed had a positive effect on ER, porosity and WSI, whereas it was negatively influenced the hardness, BD and aw. By increasing the pumpkin-flour ratio in the feed composition, both air cell size and wall thickness of samples had been decreased. The results showed that 44.2% pumpkin flour, 22% feed moisture, and 172.1 rpm screw speed gave an optimized product. There was no significant difference between predicted and experimental values (except for ER) and the variation between the values was lower than 10%. The optimized snack was a good source of fiber (around 15%), protein (17.3%), and antioxidants (TPC = 15.28 mg GAE.g-1 and antiradical scavenging activity (DPPH) = 33.66%). The caloric value of optimized snack was 362.6 cal.100g-1