Bioactive, chemical, and nutritional characteristics of coffee silverskin from pure Arabica and an Arabica–Robusta (80:20) blend

Abstract

Coffee silverskin (CS) presents a promising source of valuable nutrients and bioactive compounds, offering potential for food and nutraceutical applications. The aim of this study was to perform a comprehensive evaluation of the chemical, nutritional, and antioxidant properties of CS derived from pure Arabica (100%) and an Arabica: Robusta blend (80:20%). Analyses included proximate composition, fiber, minerals, vitamins, amino and fatty acid profiles, phenolic composition and antioxidant activity, as well as the in vitro digestion effect on total phenolic content. Both CS types exhibited high fiber content (~ 60%), moderate protein content (14-14.6%) and substantial mineral levels, particularly calcium, magnesium and iron. Notable differences were observed in amino acid and fatty acid profiles, with both samples showing unfavorable lipid quality indices. The antioxidant activity was strong across all tested assays (ABTS, DPPH, FRAP), with the Arabica: Robusta sample showing higher DPPH radical-scavenging activity despite a lower total phenolic content. Polyphenol profiling revealed that Arabica CS was richer in catechins, whereas Arabica: Robusta contained higher levels of chlorogenic and 4-hydroxybenzoic acids. Following in vitro digestion, the retention of phenolic content was higher in Arabica: Robusta CS (73.1%) than in Arabica CS (48.2%), although this difference did not reach statistical significance ( p  = 0.061). These findings highlight differences in the nutritional and functional characteristics of CS obtained from different commercial coffee formulations and support its valorization as a sustainable ingredient in health-oriented food systems.