Comparative Analysis of Dietary Fiber in Fermented Plant-Based Yogurts

Thesis Abstract

Fermented plant-based yogurts have emerged as a resilient alternative to dairy yogurts, yet there is limited comparative understanding of how fermentation processes and plant matrices influence dietary fiber content, composition, and bioavailability. This study addresses the problem of inconsistent fiber quantification and variability in functional fiber attributes across plant-based yogurts produced from soy, almond, coconut, and oat bases. The aim is to comparatively analyze dietary fiber content, composition (soluble and insoluble fractions, arabinoxylans, ?-glucans, resistant starch), and in vitro fermentability, to elucidate determinants of fiber quality in fermented plant-based yogurts. Specific objectives include (i) quantify total and fractionated dietary fiber using AOAC enzymatic-gravimetric methods and high-performance liquid chromatography (HPLC) for monosaccharide profiling; (ii) compare changes in fiber profiles before and after fermentation across four plant bases (soy, almond, coconut, oat) using analysis of variance (ANOVA) and post hoc tests; (iii) assess in vitro fermentability and short-chain fatty acid (SCFA) production using a human-colon microbiota-inspired batch culture model with gas production measurements and gas chromatography for SCFA quantification; (iv) identify processing and formulation factors driving fiber retention and modification with regression analysis; and (v) synthesize findings within a theoretical framework of the Food Structure–Fiber Interaction model and the Theory of Planned Behavior to interpret consumer-relevant implications for product development and consumption. The study adopts a cross-sectional comparative design. A laboratory-based experimental approach will be conducted with six replicates per plant base, totaling 24 yogurt samples, produced under standardized fermentation conditions, with baseline and post-fermentation fiber analyses. Data collection instruments include AOAC-approved enzymatic-gravimetric fiber assays, acid and alkaline hydrolysis for complex polysaccharide characterization, HPLC for monosaccharide composition, gas chromatography for volatile SCFA profiling, and a validated in vitro fermentation assay using a pooled human fecal inoculum. Validity and reliability will be ensured through calibration curves, method blanks, reference standards, duplicate analyses, and inter-laboratory comparison for a subset of samples. Data analysis will incorporate descriptive statistics, one-way and two-way ANOVA to compare fiber fractions across bases and fermentation stages, manova for multivariate fiber profiles, and multiple linear regression to identify shaping factors (protein content, fat, moisture, fermentation duration, starter cultures). The conceptual model integrates the Food Structure–Fiber Interaction framework to connect matrix properties and fiber retention with fermentation-induced modifications, while ancillary hypotheses drawing on the Theory of Planned Behavior will interpret anticipated consumer acceptance based on perceived fiber benefits and product attributes. Expected findings anticipate higher soluble fiber fractions in oat-based yogurts post-fermentation due to fermentative solubilization, with soy and almond matrices showing variable retention linked to protein-polyphenol interactions, and coconut-based yogurts exhibiting relatively lower fermentable fiber due to higher fat content and thermal processing effects. In vitro fermentation is expected to yield differential SCFA profiles, with higher acetate and propionate generation in oat and soy matrices, correlating with soluble fiber content. The study contributes to knowledge by providing a comprehensive, methodologically rigorous cross-sectional map of dietary fiber dynamics in fermented plant-based yogurts, offering a standardized protocol for fiber assessment in non-dairy ferments and identifying formulation strategies to optimize dietary fiber quality and health potential. Practical implications include recommendations for selecting plant bases and fermentation parameters to maximize health-relevant fiber fractions and fermentation-derived bioaccessible fiber, informing product development and labeling. The main conclusion is that fermentation and matrix composition jointly determine dietary fiber quantity and quality in plant-based yogurts, with oat-based systems showing the most favorable fiber transformation profile. Recommendations include standardizing fiber analysis in industry practice, optimizing fermentation controls to sustain soluble fiber content, and encouraging formulation of plant-based yogurts with targeted fiber profiles to enhance consumer health outcomes.