Comparative Study of Fermentation Profiles in Fermented Dairy Alternatives

Thesis Abstract

This study addresses the growing consumer demand for dairy alternatives and the limited understanding of how fermentation processes influence sensory, nutritional, and functional attributes across plant- and nut-based beverages. The aim is to compare fermentation profiles among representative fermented dairy alternatives—soy milk, almond milk, and oat milk—to elucidate how different substrates and microbial consortia shape product quality, safety, and potential health benefits. Specific objectives are (i) to characterize baseline physicochemical properties (pH, titratable acidity, water activity, viscosity) of each substrate prior to fermentation; (ii) to profile microbial community dynamics and metabolite production using 16S rRNA sequencing and gas chromatography–mass spectrometry (GC–MS); (iii) to evaluate fermentation performance under standardized conditions with two starter cultures (Lactobacillus plantarum and Streptococcus thermophilus) and a defined co-culture, across a 21-day ripening period; (iv) to assess sensory attributes via a trained panel and correlate with instrumental measurements (electronic nose and tongue); (v) to determine nutritional and functional implications by measuring protein bioavailability (in vitro simulated digestion) and antioxidant capacity (DPPH and ABTS assays). A mixed-methods experimental design is employed, integrating a randomized complete block design with substrate-specific replicates (n=12 per substrate per culture condition) to ensure robust comparisons. Data collection instruments include flow cytometry for viability, high-performance liquid chromatography (HPLC) for organic acids, nuclear magnetic resonance (1H-NMR) for metabolomic profiling, and validated sensory evaluation protocols adhering to ISO standards. Validity and reliability are established through calibration curves, triplicate analyses, inter-rater reliability for sensory data, and cross-validation of metabolomic identifications against authenticated standards. Descriptive statistics summarize baseline characteristics, while inferential analyses utilize repeated-measures ANOVA to compare fermentation kinetics (pH, acidity, microbial counts) across substrates and cultures, followed by multivariate analyses (Principal Component Analysis and Partial Least Squares Discriminant Analysis) to associate metabolite signatures with sensory and nutritional outcomes. A conceptual framework rooted in the fermentation theory of microbial synergy and the substrate-specific enzyme milieu informs model specification, with corroboration from the Theory of Food Matrix Interactions to explain matrix effects on microbial metabolism. It is anticipated that fermentation will produce substrate-dependent profiles plant bases rich in carbohydrates will favor organic acid production and exopolysaccharide-mediated viscosity changes, whereas protein-rich matrices will influence peptide-derived bioactivities and peptide-modulated flavor compounds. Expected findings include distinct volatile and non-volatile metabolite fingerprints for each substrate, differential microbial succession patterns, and measurable differences in protein digestibility and antioxidant capacity linked to specific fermentation trajectories. The study contributes to knowledge by providing a rigorous cross-sectional comparison of fermentation outcomes across diverse fermented dairy alternatives, integrating microbiology, metabolomics, sensory science, and nutrition to inform product development, quality control, and consumer health considerations. The results are expected to reveal actionable insights for selecting substrate–culture combinations that optimize texture, flavor, safety, and nutritional quality while maintaining consumer acceptability. Based on the findings, recommendations will address formulation strategies, process parameters, and standardization of fermentation protocols for commercial production of fermented dairy alternatives, along with guidance for regulatory labeling of nutritional and functional claims. The study concludes that substrate identity and microbial consortium composition jointly determine fermentation profiles, with implications for tailoring fermentation to maximize desirable sensory properties and health-promoting attributes in fermented dairy alternatives.