Effect of extrusion process conditions on the physical properties of tef-oat healthy snack extrudates

Abstract

Tef with different oat blend ratio was processed in a single screw extruder and evaluated for optimum physical and protein quality. Effects of oat level (0–30%), feed moisture content (12–16%), extruder die temperature (DT) (80–140 °C), and screw speed (SS) (80–200 rpm) on the extrudate characteristics were investigated using Box–Behnken design. The addition of oat level above 15% increased the extrudate protein availability and water absorption capacity. DT greater than 110 °C and feed moistures greater than 14% results in a steep increase in expansion ratio. The pasting property of tef flour showed higher initial (56 cP) and final viscosity (102 cP) than oat flour with 48 cP initial viscosity and 56 cP final viscosity. In conclusion, tef with 29% oat blend, 16% feed moisture, 140 °C DT, and 80 rpm SS gave an optimum product with high desirability (>0.8). Practical applications The demand for healthy snack formulation with low glycemic index is increasing with the snack industry. Extrusion cooking provides control on minimising the nutrient loss with improved functional qualities. The study provides new experimental data of extrusion process parameters for teff and oat flour formulation. The effect of extrusion process conditions on the extrudate physical and protein quality was optimized using response surface methodology. The pasting profile and gelatinization temperature of tef-oat formulation indicated their potential application in food textural modifications. The results obtained will be of great significance for formulation and development of healthy snack with minimal loss of nutrients during processing.