Orange Juice Enriched With Blood Orange Pomace: Effect of Fermentation by Lactic Acid Bacteria and In Vitro Digestion on Orange Bioactive Compounds

This study aims to explore the potential of enhancing orange juice (OJ) with blood orange pomace, analyzing both non-fermented and fermented varieties, as well as the simultaneous fermentation of the juice with 2.5% and 5% added blood orange pomace, while characterizing OJs produced through various strategies. The viable Lactobacillus counts, physicochemical characteristics, total phenolic content (TPC), and antioxidant activity were examined during the in vitro digestion of prepared OJs. Before fermentation, OJs enriched with 2.5% and 5% blood orange pomaces exhibited the highest Lactobacillus viability, measuring 8.52 ± 0.17 and 8.61 ± 0.15 log colony forming unit (CFU)/mL, respectively, in consistency with the pH values. The fortification of OJ with blood orange pomace also resulted in improved TPC and antioxidant capacity, both prior to and following in vitro digestion. The OJ containing fermented blood orange pomace at a concentration of 5% (w/w) demonstrated the most favorable results. Metabolomic analysis identified 3308 metabolites, with 1260 showing significant differences before and after fermentation, including the upregulation of phenols, organic acids, and other bioactive compounds with antioxidant properties. KEGG pathway enrichment analysis revealed substantial alterations in arachidonic acid metabolism and taurine and hypotaurine metabolism, which are closely associated with the observed biochemical transformations. These metabolic changes suggest that fermentation enhances the nutritional profile of OJ and promotes the generation of functional metabolites, contributing to improved antioxidant activity and health benefits.