Low Moisture Extrusion of Intermediate Wheatgrass-Pea Starch Blends: Production and Characterization of Ready-to-Eat Extruded Snacks

Abstract Intermediate wheatgrass [IWG; Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], enriched with protein and dietary fiber, has the potential to deliver both food and ecosystem service benefits. However, its lower starch content limits expansion of the extrudates during extrusion, reducing its suitability for puffed ready-to-eat (RTE) snacks. Pea starch, a by-product in pea protein production, can enhance functional attributes of extruded products. Therefore, this systematic study was conducted to optimize the extrusion parameters to produce RTE snacks through a co-rotating twin-screw extruder to meet the increasing demand for nutritious novel foods. Box-Behnken design coupled with response surface methodology was used to investigate the effects of pea starch percentage, feed moisture, screw speed and barrel temperature on product responses (expansion ratio, bulk density, hardness, crispiness, color (L*), water absorption index, water solubility index) and processing response (specific mechanical energy) whose value varied from 1.08 to 2.16, 0.13 to 0.34 g/cm 3 , 30.33 to 109.74 (N), 284.68 to 751.43 N.s, 72.71 to 80.55, 4.49 to 6.59 g/g, 21.45 to 35.91% and 586.40 to 1132.09 kJ/Kg respectively. Response surface regression models were established to determine the response variables. Regression models for all the responses were highly significant ( p < 0.01) with coefficient of determination ranged from 0.62 to 0.98. The optimum conditions obtained by multi-response optimization for the development of RTE extruded snacks were IWG flour to pea starch ratio (46:54), feed moisture 19.57%, screw speed 241 rpm and barrel temperature 131 °C. This paper therefore explores the optimization of processing conditions for the development of RTE extruded snacks from IWG-pea starch blends.