Development and validation of a probiotic yogurt using novel plant-based fermentation substrates

Thesis Abstract

The increasing demand for functional dairy products with enhanced health benefits necessitates the exploration of innovative fermentation substrates that are both nutritionally rich and sustainable. This study addresses the challenge of developing probiotic yogurt using novel plant-based fermentation substrates, with the aim of creating a nutritious, culturally acceptable, and economically viable functional dairy alternative. Specifically, the objectives include evaluating the physicochemical, microbiological, and sensory properties of the yogurt, validating probiotic viability during storage, and establishing the product’s shelf life and consumer acceptability. The research adopted a mixed-methods approach within a quasi-experimental design framework. The study population comprised 150 adult consumers aged 18–65 years within urban regions, selected through stratified random sampling to ensure demographic diversity. The primary experimental sample consisted of 50 batches of yogurt, prepared using locally sourced plant-based substrates—including sorghum, millet, and spirulina extract—in substitution for conventional dairy. Key data collection instruments included microbiological assays employing standard plate count techniques for probiotic enumeration, physicochemical analysis using pH meter, titratable acidity, and moisture content determination, and sensory evaluation conducted via hedonic scaling with a panel of 30 trained evaluators. The study further employed high-performance liquid chromatography (HPLC) to quantify bioactive compounds and probiotic metabolites. To verify probiotic stability during storage, samples were analyzed at intervals of 0, 7, 14, and 21 days under refrigerated conditions. Validity and reliability of instruments were confirmed through calibration, repeatability tests, and pilot studies, while data analysis employed analysis of variance (ANOVA) to compare physicochemical and sensory parameters across formulations, and regression analysis to evaluate probiotic viability decline over time. A modified Food-Energy-Environment model was adapted to interpret the interrelationship of ingredients, microbial survival, and sensory acceptance. Expected findings reveal that plant-based substrates can effectively support probiotic growth, maintaining viable counts above the recommended threshold of 10^6 CFU/mL throughout the shelf life. Physicochemical parameters are anticipated to show significant differences compared to traditional yogurt, with enhanced antioxidant properties attributable to spirulina, and altered pH and acidity levels conducive to probiotic stability. Sensory analysis is projected to demonstrate high consumer acceptability, with preference for formulations incorporating millet and spirulina, owing to their distinct color and flavor profiles. The study expects that probiotic counts remain stable, and bioactive compounds such as phycocyanins and flavonoids are retained during storage, implying potential health benefits. This research contributes new knowledge to the field of functional foods by validating the feasibility of utilizing underexplored plant substrates as fermentation media for probiotic yogurt production, thereby broadening the scope of sustainable and culturally tailored probiotic foods. It also offers critical insights into the interplay between plant matrix composition and probiotic survival, informing future product optimization. The study concludes that plant-based fermentation substrates are promising alternatives to dairy in probiotic yogurt manufacturing, with implications for improving nutritional security and catering to plant-based dietary preferences. Based on findings, recommendations include scaling up production processes, conducting long-term consumer acceptance studies, and investigating operational feasibility in commercial settings. Future research should explore bioavailability of functional compounds, incorporating molecular microbiology techniques such as quantitative PCR to further elucidate probiotic strains’ behavior. The study affirms the potential of plant-based substrates to expand the diversity of functional probiotic foods, promoting healthier diets and sustainable food systems.