Assessing changes in grape pomace-maize flour mixtures and extruded products

The development of novel functional ready-to-eat foods is an actual concern of the industry. In this context, this paper proposes the use of a non-conventional ingredient (grape pomace) in the production of maize expanded products. Seedless (SGPW) and whole (GPW) white grape pomace were incorporated in maize flour (10-40%) and the features of the flour mixtures (color, thermal properties, molecular characteristics) and final product quality (color, texture, expansion ratio, chemical composition, starch fractions, sensory and microstructure) were evaluated. The addition of grape pomace resulted in a reduction of enthalpy from 1.9 to 0.4 J/g, chroma from 27.4 to 21.3, and hue angle (from 1.2 to 1.0) of flour mixtures. The color difference and the FT-IR absorbance intensities increased proportionally with the amount added. Fortification of maize expanded products determined the increase of total polyphenols from 11.73 to 33.15 mg GAE/g, fiber from 0.42 to 20.68%, protein, fat, ash, rapid and total digestible starch from 30.0 to 42.3%, and radical scavenging activity from 38.04 to 94.84%, while the resistant and slowly digestible starch decreased. A reduction of the texture properties, expansion ratio from 3.32 to 2.66, and chroma from 21.7 to 12.9 of the expanded products was obtained due to the rising addition level. Considering the sensory analysis results, an addition level up to 30% SGPW and 20% GPW will be acceptable. These results highlight how a fiber and polyphenol-rich by-product like grape pomace alters starch functionality, texture, and sensory properties in extruded systems while advancing both scientific understanding and sustainable formulation practices. • Molecular and thermal properties of maize were changed by grape pomace (GP) depending on the dose. • ●GP modified the starch digestibility of the extrudates by increasing total digestible starch. • ●Nutritional and bioactive compounds content increased with the increase in GP level. • ●Expansion ratio and texture decreased proportionally with the GP level rise. • ●From a sensory point of view, 30% seedless and 20% whole GP will be acceptable.