Coffee (Coffea arabica L.) Silverskin: Transforming a Recycled By-Product Into Natural Antioxidant Ingredients for Ready-to-Eat Fish Products.

Given salmon's high susceptibility to oxidation and the need for sustainable food processing, this study evaluated the technological potential of incorporating 0.5% coffee silverskin (CSS), using two specific materials evaluated in this study, namely, artisanal (ACS) and industrial (ICS) coffee silverskins, into restructured salmon stored under refrigeration (3°C) for 28 days (sensory analysis was limited to 14 days). ACS showed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS scavenging activity and chlorogenic acid content, whereas ICS exhibited greater ferric reducing antioxidant power (FRAP), consistent with Maillard reaction products. Regardless of antioxidant mechanism, CSS reduced lipid oxidation, lowering malondialdehyde (MDA) and volatile oxidation markers. However, 0.5% CSS did not prevent apparent protein carbonylation, with treated groups showing higher 2,4-dinitrophenylhydrazine (DNPH)-reactive carbonyl values during late storage. Although CSS darkened the product, trained-panel liking was maintained, whereas rancidity and warmed-over flavor (WOF) were reduced compared to the control, although sensory patterns varied throughout storage. These findings identify CSS as a potential natural antioxidant for enhancing oxidative stability and supporting the sustainable valorization of coffee industry by-products, although further optimization may be needed to overcome sensory limitations and support its broader application. PRACTICAL APPLICATIONS: Coffee silverskin (CSS), a coffee roasting by-product, is a potential natural antioxidant for improving oxidative stability and delaying rancidity in ready-to-eat restructured fish. Its comparative performance across the two evaluated sources supports its potential use as a clean-label antioxidant ingredient while promoting circular economy practices.