Pisco grape pomace: Iron/copper speciation and antioxidant properties, towards their comprehensive utilization

Abstract

The pisco and wine industry produces hundreds of tons of grape pomace each year in Chile, generating environmental problems, and demanding urgent strategies for its management. The aim of this work was to study the pisco grape pomace based on a physicochemical characterization, an iron/copper speciation analysis, and the optimization for polyphenols recovery, establishing the polyphenolic profile, antioxidant properties, and the Fe2+/Cu2+ chelating activity, to promote their revalorization as an ingredient with potential application in the food industry. The chemical characterization showed mainly high values for crude protein (15.36% dw) and potassium (9240.66 mg/kg). The Fe/Cu speciation depicted that iron and copper soluble forms in pisco pomace flour represented 70.57% and 52.18%, respectively, regarding total content. The optimized extract showed mainly pyrogallol, catechin and epicatechin, with concentrations of 1078.43 ± 60.14 μg/g, 883.20 ± 7.57 μg/g and, 751.76 ± 23.04 μg/g, respectively, with a relevant antioxidant capacity by Oxygen Radical Absorbance Capacity (ORAC) of 1402.15 μmol TE/g dw GPE and, a better chelating ability to complex Fe2+ than Cu2+. The pisco pomace was for the first time chemically characterize, showing it as a potential source of minerals and antioxidant biocompounds, making it a good candidate for nutritional applications, as a rich source of organic matter or even could be potentially utilized to produce value-added commodities, toward a circular economy.