Fermentation - Assisted Valorization of Pomegranate Peel: A Contribution to Resource Efficiency and Circular Bioeconomy

Abstract

The valorization of pomegranate peel is constrained by the cost and complexity of conventional extraction and purification technologies. The present study proposes a fermentation-assisted process designed to recover polyphenolic fractions from coarse pomegranate peel while simultaneously generating a wine-type co-product and a residual dietary-fiber fraction. The process comprises two principal stages: (i) extraction during anaerobic alcoholic fermentation mediated by Saccharomyces cerevisiae and (ii) sequential fractionation of the resulting hydro-ethanolic extract through spontaneous sedimentation and gelatin-induced precipitation. Three polyphenol-rich precipitates were obtained during clarification, while the remaining liquid phase was retained as a dry red wine-type product designated “Aztanna”. Under the selected conditions, coarse peel was fermented for 14 days at 18–22 °C at a peel-to-water ratio of 1:1.5–1.6, with 18% added sucrose and S. cerevisiae. For sample 1, the selected conditions yielded 66.63% recovery of total polyphenols into the liquid extract; for sample 3, the corresponding recovery was 76.74%. During maturation of the extract from sample 3, the insoluble polyphenolic fraction increased from 12.22% after 3 days to 26.00% after 90 days. In a 100-kg peel scenario, the process was calculated to yield approximately 670 g ellagic-acid-rich fraction, 150 g gelatin-tannate, 425 g α-glycosides, and 154.4 L of clarified wine-type extract, in addition to a dietary-fiber residue. The principal technological advantage of the proposed approach is the elimination of several energy- and equipment-intensive operations used in conventional workflows, including drying and fine grinding of the raw peel, thermal maceration, and adsorption chromatography. The results support further pilot-scale evaluation of the process as an integrated valorization route for pomegranate-processing by-products.