Impact of Fermentation Conditions on Nutrient Retention in Plant-Based Yogurt Alternatives via Field Trials

Thesis Abstract

Fermentation is a critical process in shaping the nutritional quality and sensory attributes of plant-based yogurt alternatives; yet, field-scale fermentation conditions and their direct impact on nutrient retention under variable real-world production contexts remain insufficiently understood. This study addresses the problem by examining how controlled versus non-controlled fermentation parameters influence retention of vitamins (B2, B12, folates), minerals (calcium, iron, zinc), and macronutrient integrity (protein digestibility) in plant-based yogurts derived from soy, almond, and oats under diverse field conditions. The aim is to quantify the effects of fermentation temperature, pH trajectory, inoculum concentration, and sequential fermentation steps on nutrient retention, while accounting for raw material heterogeneity and ambient environmental fluctuations. The specific objectives are (1) to determine the relationship between fermentation temperature regimes (ambient vs. controlled 28–32°C and 34–38°C) and retention of target micronutrients across plant bases; (2) to assess the influence of pH trajectories (rapid drop to pH 4.5–4.8 versus gradual decline) on protein integrity and mineral bioavailability; (3) to evaluate the effect of starter culture concentration (1%, 2%, 3% v/v) on nutrient preservation; (4) to compare single-step versus two-step fermentation on overall nutrient retention; and (5) to develop a predictive model linking fermentation parameters to nutrient outcomes applicable to field-scale production. The methodology adopts a mixed-methods, comparative field trial design conducted over three production cycles in three collaborating dairy-replacement facilities. The population comprises commercial plant-based yogurt facilities using soy, almond, and oat bases. Samples (n=360) are drawn across nine fermentation runs (three bases × three sites) with two fermentation regimes per site and three inoculum levels. Data collection employs quantitative analyses, including high-performance liquid chromatography (HPLC) for B2, B12, and folate profiling, inductively coupled plasma mass spectrometry (ICP-MS) for minerals, and in vitro protein digestibility assays. Nutritional data are complemented by process monitoring logs capturing temperature, pH, and time-to-coagulation. Validity and reliability are ensured through calibration with standard references, duplicate analyses, and inter-laboratory cross-checks. Data analysis follows a hierarchical mixed-effects model to assess main effects and interactions of fermentation variables on nutrient retention, with fixed effects for base, regime, inoculum level, and site, and random effects for batch and operator. ANOVA and post-hoc Tukey tests examine differences across treatment groups, while regression analyses generate predictive equations for nutrient retention as functions of fermentation parameters. A structural equation modeling approach tests the direct and indirect pathways linking process variables to nutrient outcomes. Sensitivity analyses evaluate robustness to raw-material variability. The study is anchored in the fermentation theory of microbial metabolism and nutrient transformation, supported by the growth-associated maintenance energy model and the bioavailability framework for trace minerals, alongside the food processing theory of heat and pH-induced nutrient stability. Theoretical lenses include the Process-Structure-Function paradigm and the Innovation Diffusion in Food Processing, augmented by risk perception theory to interpret stakeholder responses to process changes. Anticipated findings indicate that controlled fermentation temperature and moderated pH decline enhance retention of folates and B12 while minimizing mineral losses, with a positive effect of moderate starter concentrations on protein integrity. Two-step fermentation is expected to improve folate and zinc retention relative to single-step processes, albeit with marginal gains for some bases. The study contributes new field-validated evidence on how exploitable fermentation controls improve nutrient retention in plant-based yogurts, enabling better product labeling, process optimization, and nutrition-aware consumer guidance. Practical implications include recommended ranges for fermentation temperature, acidification rate, and inoculum levels tailored to plant base type, supported by a user-friendly predictive model for industry adoption. The final conclusion emphasizes that meticulous control of fermentation conditions significantly enhances nutrient retention in plant-based yogurt alternatives under real-world production variability, and recommendations are provided for standardizing fermentation protocols, implementing real-time monitoring dashboards, and pursuing cultivar- or base-specific optimization studies to further maximize nutritional quality.