In recent years, there has been a surge in the production of kombucha—a functional beverage obtained via microbial fermentation of tea. However, fres

Roasted coffee silverskin (RCSS) is a by-product of coffee production characterized by its content of phenolic compounds, both free and bound to macromolecules. In this study, RCSS was fermented to release these compounds and consequently increase its value as a functional food ingredient. Fermentation was carried out using yeast, acetic acid bacteria, and lactic acid bacteria, either as single strains or as a designed microbial consortium. The latter included Saccharomycodes ludwigii, Gluconobacter oxydans, and Levilactobacillus brevis, mimicking a symbiotic culture of bacteria and yeast commonly used in kombucha fermentation (SCOBY). This symbiotic microbial culture consortium demonstrated notable efficacy, significantly enhancing the total phenolic content in RCSS, with values reaching 14.15 mg GAE/g as determined by the Folin–Ciocalteu assay and 7.12 mg GAE/g according to the Fast Blue BB method. Antioxidant capacity improved by approximately 28% (ABTS) and 20% (DPPH). Moreover, the fermented RCSS supported the viability of probiotic strains (Saccharomyces boulardii SB01 and Levilactobacillus brevis ŁOCK 1152) under simulated intestinal conditions. These results suggest that RCSS, particularly after fermentation with a full symbiotic microbial culture consortium, has strong potential as a clean label, zero-waste functional food ingredient.

Roasted coffee silverskin (RCSS) is a by-product of coffee production characterized by its content of phenolic compounds, including those contributing to bitterness. The aim of this study was to evaluate RCSS as an analog for hops in the production of non-alcoholic beer. Beers were developed using hops, RCSS, or a combination of both. Their sensory and physicochemical properties were evaluated, including bitterness, total phenolic content, and antioxidant capacity. Compared to hopped beer, the RCSS beer exhibited a significantly higher original gravity (7.11°P vs. 6.70°P), apparent extract (6.52°P vs. 6.20°P), and darker color (18.02 vs. 4.65 EBC). The total phenolic content was also significantly higher in the RCSS beer, reaching 0.51 ± 0.03 mg CGA/mL, which represents a 34% increase compared to the hopped variant. Importantly, the addition of RCSS had no negative effect on fermentation process. Moreover, the RCSS beer was characterized by improved overall sensory quality. These results indicate that RCSS is an innovative, sustainable alternative to hops, enhancing both sensory and functional properties while supporting zero-waste brewing strategies.