Physicochemical Properties and Mechanisms of Oil‐In‐Water Emulsion Formation and Stabilization by Yeast Protein Ingredients From <i>Saccharomyces cerevisiae</i> and <i>Candida utilis</i>

ABSTRACT This study explored the nutrient composition, protein profile, physicochemical and emulsifying properties of commercial yeast protein ingredients, including a Saccharomyces cerevisiae protein concentrate (YPC) and a Candida utilis biomass (YB), with a view to enabling their use in food applications. YPC and YB exhibited low solubility in water across the pH range of 2–9 due to the high density of the yeast cells, in which most of the proteins are located. Investigation of the emulsifying properties of these ingredients, using model oil‐in‐water systems (1–5 wt% protein, 10 wt% oil, pH 6.8), showed that while emulsion formation could be attributed to the soluble phase, comprising proteins and potentially other surface‐active compounds, the presence of yeast cells improved stability over 30 days of refrigerated storage through a steric mechanism. A protein‐to‐oil ratio greater than 1:10 prevented oil droplet coalescence, and the inclusion of a food‐grade stabilizer, such as gellan gum (0.15 wt%), to increase the viscosity of the continuous phase, provided colloidal stability throughout the storage period for all emulsions. Differences were observed in the properties of the emulsions produced using YPC and YB, which may be explained by their cell size and morphology, the composition of the cell wall, and the soluble protein concentration and profile. Taken together, the results show that commercial yeast protein ingredients can form physically stable oil‐in‐water emulsions when appropriate protein‐to‐oil ratios and continuous phase viscosity are employed.