Integrated Microbial Characterization, Safety Evaluation and Nutritional Profiling of Selected Nigerian Fermented Foods

Abstract

Background: Fermented foods are integral to diets worldwide, particularly in Africa, where they enhance food security, nutrition, and cultural heritage through the activity of diverse microorganisms that improve food quality and functionality. Aim: This study presents an integrated evaluation of the microbial profile, safety status, and nutritional composition of selected Nigerian fermented foods, namely yoghurt, nunu, ogiri, and ugba. Study Design: Standard microbiological and analytical methods were employed. Methods: Fermented food samples – yoghurt, nunu, ogiri and ugba were obtained. Samples were analyzed to determine total viable count (TVC), total fungal count (TFC), lactic acid bacteria (LAB), microbial identity, and proximate composition. Results: The study showed significant variations (p < 0.05) among samples, with ogiri and ugba exhibiting higher microbial loads of 3.4 × 10⁸ and 4.2 × 10⁸ cfu/mL compared to yoghurt and nunu of 6.1 × 10⁶ and 3.5 × 10⁶ cfu/mL, respectively. LAB counts were significantly highest in Ugba with 1.0 × 10⁹ cfu/mL, indicating strong fermentative activity and potential probiotic functionality. Identified bacterial genera included Lactobacillus, Streptococcus, and Enterococcus, alongside opportunistic contaminants such as Enterobacter and Staphylococcus. Fungal isolates included Saccharomyces spp. in ogiri and Aspergillus spp. in Ugba. Proximate analysis revealed that Ogiri and Ugba had significantly higher protein content at 26.34% and 19.20%, respectively, while yogurt had the lowest at 3.88%.  Ogiri and nunu had the highest fat content at 7.55% and 4.78%, respectively. Conclusion: The findings highlight the dual nature of traditional fermented foods as nutritionally valuable yet microbiologically complex systems. While their high LAB content supports the potential of functional foods, the presence of contaminants underscores the need for improved hygiene practices and controlled fermentation techniques to ensure safety and quality.