Stability and Functionality of Grape Pomace Used as a Nutritive Additive During Extrusion Process

Abstract

Grape pomace (GP) is a major byproduct of wine and juice industry, rich in polyphenolics with demonstrated health benefits. Extrusion processing for development of healthy and quality GP supplemented corn starch snack foods was evaluated using response surface methodology. The retainability of polyphenolic content and antioxidant activity after extrusion processing were further assessed. The processing variables were feed moisture (16, 20, and 24 ± 0.2% w.b.), screw speed (150, 200, and 250 rpm), and the level of GP supplementation (0, 5, and 10% w/w). Extrudates with 5% GP and 16 ± 0.2% feed moisture had a high overall expansion ratio (ER) of 3.83 ± 0.14, and overall low density (0.11 ± 0.00 g/cm3). Total polyphenolic content (TPC) of the extrudates (5% GP, and 16% feed moisture) extruded at 150 and 250 rpm retained up to 74.1% and 78.57% respectively, while TPC was retained at 95% when extruded under 200 rpm with 10% GP and 16% feed moisture. Additionally, the total antioxidant activity and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of the 5% GP extrudates retained 98% after extrusion processing. Moreover, polyphenolic extract of 5% GP extrudates suppressed reactive oxygen species (ROS) in CaCO2 cells induced by hydrogen peroxide. In conclusion, GP incorporation in cornstarch extrudates improved both the physicochemical quality as well as nutritional value of products. Our study indicates that GP can be effectively incorporated into extruded foods by providing enhanced nutritional value without losing the expansion characteristics.