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 cornstarch 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 of 3.83 ± 0.14, and overall low density (0.11 ± 0.00 g/cm 3 ). 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 scavenging activity of the 5% GP extrudates retained 98% after extrusion processing. Moreover, polyphenolic extract of 5% GP extrudates suppressed reactive oxygen species in Caco-2 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.

Utilization of Food Processing By-products in Extrusion Processing: A Review

“…For example, the hardness of corn-mango peel extrudates increased as the mango peel content exceeded 8% (Mazlan et al, 2019). Similar observations were reported in the studies of grape pomace, tomato pomace, and broccoli trimming (Altan et al, 2008a,b;Bisharat et al, 2013;Bibi et al, 2017). On the contrary, the amount of pineapple pomace added did not affect the hardness of extrudates (Selani et al, 2014).…”

“…High SDF, high sugar content, and low crystallinity index could be the reason for the highest expansion for apple pomace, among others. Another study with grape pomace also explained that high sugar content in grape pomace could be the reason for the increase in expansion ratio of extrudate with 5% of grape pomace, compared to the control (Bibi et al, 2017). In another study on apple pomace addition to regular and waxy cornstarch showed that extrudates with 15% inclusion of apple pomace had similar or even higher ER than the control in some conditions (Masli et al, 2018a).…”

“…The overall WSI values of extrudates decrease with increasing by-product inclusions (Selani et al, 2014;Kaisangsri et al, 2016). However, the WSI of grape-pomace enriched extrudates increased with grape pomace at the low moisture content (16%), while WSI values decreased with pomace at the high moisture content (24%) (Bibi et al, 2017). It could be attributed to the degradation of starch and the breakdown of grape pomace into the more soluble fiber at a high energy input of extrusion due to the low moisture content in this case.…”

“…However, these two properties are significantly influenced by the combined effects of raw materials, the expansion of the extrudates, and the processing conditions. WAI values were reported to increase with the increase of grape pomace (Bibi et al, 2017), carrot pomace (Kaisangsri et al, 2016), and cauliflower trimming (Stojceska et al, 2008a). The authors attributed these results to the water absorption capability of fiber present in the by-products.…”

“…The high retention was attributed to the combined effect of feed moisture content, shear stress, and temperature, which degrade the compounds or cause their transformation to easily extractable forms (Leyva-Corral et al, 2016). Total phenolic compounds of grape-pomace enriched extrudates retained ∼75 at 5% inclusion, and there was no significant loss at 10% inclusion of grape pomace before and after extrusion (Bibi et al, 2017). The total antioxidant activity of extrudates was retained to approximately 90% compared to raw mixtures.…”