Vernonia amygdalina as a hop substitute in red sorghum beer: Effects on fermentation performance and physicochemical properties

Abstract

The substitution of imported hops with locally available botanical alternatives offers a sustainable strategy for sorghum-based beer production. This study evaluated partial and total replacement of hops with <i>Vernonia amygdalina</i> as a bittering agent on fermentation performance and physicochemical properties of red sorghum malt beer. Five formulations were prepared with 0, 25, 50, 75, and 100% (w/w) substitution and fermented for 192 h using <i>Saccharomyces cerevisiae</i> (brewer's yeast strain ANGEL BF-16) under controlled laboratory conditions. <i>V. amygdalina</i> was added at the end of the 60-min boil, immediately before cooling, to maximize extraction of bitter compounds while preserving heat-sensitive aromatic molecules. Fermentation kinetics and final beer characteristics were assessed via extract content, density, alcohol concentration, pH, color (EBC), and apparent attenuation. Increasing proportions of <i>V. amygdalina</i> significantly enhanced fermentation, yielding higher alcohol content (5.2-6.3% v/v), increased apparent attenuation (61.6-75.5%), and lower final pH values compared to the hop-only control. Higher substitution levels also increased color intensity, reflecting contributions of plant-derived pigments and polyphenols. Microbiological analyses confirmed the absence of detectable contaminants, indicating that <i>V. amygdalina</i> did not inhibit yeast activity. Statistical analysis showed that fermentation duration and bitter extract formulation significantly affected all measured variables (p < 0.05). Although sensory evaluation and detailed phytochemical profiling were not performed, results indicate that <i>V. amygdalina</i> is a viable hop substitute with measurable effects on fermentation efficiency and beer quality. Future studies should investigate sensory acceptance and optimize substitution levels for industrial application.