SHELF-LIFE AND SENSORY ACCEPTABILITY OF YEAST-TREATED AND UNTREATED TRADITIONAL BEVERAGES UNDER AMBIENT STORAGE CONDITIONS

Abstract

Traditional Nigerian beverages, including Kunun zaki, Kunun aya, Zobo, Ginger Drink, and Fura, are widely consumed for their nutritional and cultural significance but are highly perishable due to microbial contamination. This study evaluated the shelf-life and sensory acceptability of yeast-treated and untreated beverages under ambient storage conditions (25°C–30°C). Fresh samples were collected from local vendors and households in Sokoto State, Nigeria, and divided into untreated controls and samples inoculated with Saccharomyces cerevisiae (10⁷–10⁸ cells/mL). Microbiological analyses (total bacterial and fungal counts), physicochemical measurements (pH and °Brix), and sensory evaluations (taste, odor, color, and overall acceptability) were performed at 0, 24, 48, 72, and 96 h. The results showed that untreated beverages exhibited progressive increases in bacterial (up to 7.60 ± 0.60 log₁₀ CFU/mL in Fura) and fungal loads (up to 5.50 ± 0.48 log₁₀ CFU/mL), along with significant declines in pH and increases in °Brix, indicating uncontrolled microbial spoilage and chemical instability. In contrast, yeast-treated beverages maintained lower microbial loads, moderated pH declines, and minimized °Brix increases, reflecting enhanced chemical stability. Sensory evaluation demonstrated that yeast-treated samples consistently scored higher for taste, odor, color, and overall acceptability than untreated samples, indicating improved consumer preference. Naturally acidic, Zobo exhibited the greatest intrinsic stability. This study demonstrates that S. cerevisiae treatment effectively extends the shelf life of traditional beverages during ambient storage while maintaining or enhancing sensory quality. These findings highlight the potential of controlled yeast fermentation as a low-cost, natural preservation strategy, contributing to improved food safety, reduced postproduction losses, and greater consumer acceptability.