Development of a shelf-stable plant-based yogurt using novel stabilizers and fermentation design

Thesis Abstract

The global demand for shelf-stable plant-based dairy alternatives has intensified the need for yogurt-like products with credible texture, flavor, and nutritional quality while ensuring microbial safety and extended shelf life. This study addresses the challenge of developing a plant-based yogurt that remains stable under ambient and refrigerated storage through the integration of novel stabilizers and optimized fermentation design. The aim is to formulate a yogurt-like beverage from plant substrates that achieves comparable rheological properties, mouthfeel, and acidified flavor profiles to conventional dairy yogurt, with a minimum shelf life of 90 days at 4°C and 25°C. Specific objectives include (i) screening and characterizing novel stabilizers (including hydrocolloids and polysaccharide blends) for synergistic stabilization of gel network; (ii) optimizing fermentation parameters (starter culture selection, inoculation rate, incubation temperature, and time) to achieve desirable acidification kinetics and textural development; (iii) evaluating physicochemical, rheological, and sensory properties of the final product; (iv) assessing pathogen and spoilage organism safety under accelerated shelf-life conditions; and (v) performing a comparative consumer acceptability study to gauge market viability. A mixed-methods approach is employed in three sequential phases. Phase I involves a factorial screening of stabilizers (x1–x4) and their concentrations (0.2–1.5% w/w) with three plant bases (soy, almond, and oats) (n=9 formulations per base; total n=27) assessed for viscosity, syneresis, droplet stability, and pH changes over 28 days at 4°C and 25°C using a controlled environment chamber. Phase II implements a fermentation design optimization using response surface methodology (RSM) to refine starter cultures (Lactobacillus plantarum, Streptococcus thermophilus) and incubation conditions (37–42°C; 6–18 h), targeting a gel firmness of 0.6–1.2 N and a syneresis rate below 5% after 28 days. Instrumental analyses include rheometry (cone-plate viscometry), differential scanning calorimetry (DSC) for gel transition, and Fourier-transform infrared spectroscopy (FTIR) to monitor network formation. Phase III comprises a consumer sensory panel (n=120) employing a 9-point hedonic scale and CATA (check-all-that-apply) descriptors, alongside a trained panel evaluation for descriptive profiling. Data collection tools comprise calibrated rheometers, texture analyzers, pH meters, microbiological samplings for total viable count and contamination indicators, and validated sensory questionnaires. Validity and reliability are ensured through instrument calibration, pilot testing, inter-rater reliability for sensory analysis, and replication across two production days. Statistical analyses include ANOVA and Tukey post hoc tests to compare stabilizer systems, regression analyses to model texture parameters as a function of stabilizer and fermentation variables, and multivariate analysis (principal component analysis) to relate sensory attributes to instrumental measurements. The study anticipates identifying stabilizer blends that yield a cohesive gel network with reduced syneresis while maintaining high consumer acceptability. Expected findings include a demonstrable improvement in rheological stability and shelf-life extension with specific blends (e.g., xanthan–gum arabic or gellan–locust bean gum combinations) and fermentation parameters that balance acid development with textural integrity. Theoretical contributions align with food colloid theory and fermentation science, integrating the gelation and network formation concepts with starter culture dynamics to elucidate structure–function relationships in plant-based yogurt matrices. The research contributes to knowledge by providing a scalable framework for designing shelf-stable plant-based yogurts, detailing stabilizer–substrate–microbial interactions, and offering a validated methodology for evaluating long-term stability and consumer acceptance. The main conclusion is expected to show that a carefully designed stabilizer system coupled with an optimized fermentation protocol can produce a plant-based yogurt with competitive texture, flavor, and extended shelf life. Practical implications include guidance for product developers on formulation strategies, process parameters, and quality assurance protocols; recommendations for further research involve exploring alternative plant bases and environmental storage conditions to broaden market applicability.