Expanding food applications of yeast protein by microbial fermentation: techno-functional, rheological and aroma characterization

Yeast protein (YP) has been touted as a sustainable alternative to animal-based proteins. However, its food applications are hindered by several techno-functional drawbacks, such as poor solubility and low apparent viscosity. This study investigated the impact of fermentation using selected lactic acid bacteria with varying levels of proteolytic activity and producing different types of exopolysaccharide (EPS) on YP. The potential synergistic effects of ultrasonic pretreatment were also evaluated. Adding sucrose or glucose during fermentation supported EPS synthesis (e.g., 2.7–3.6 % dextran) and lactic acid production (4.3–6.3 mg/g), the latter contributing to the suppression of potential foodborne pathogens. Fermentation with Pediococcus acidilactici 10MM1significantly enhanced solubility (≥2-fold at pH 3–9), emulsifying activity (1.6-fold), and emulsifying stability (1.3-fold) of YP, attributable to the strain's high proteolytic activity. Fermentation with Weissella confusa VIII40 significantly improved viscoelastic properties and increased water-holding capacity (WHC) by 16 %, with lesser effects observed for Levilactobacillus brevis AM7 (14 %), Lactiplantibacillus plantarum B24W (11 %) and Leuconostoc pseudomesenteroides 20193 (5 %). The abovementioned improvements appeared strain- and EPS-dependent, related to mechanisms such as increased particle size (due to EPS–protein complex formation) and altered YP secondary structure (decreased α-helix content and increased random coil). Variations in the volatile profiles of YP were also strain-specific, with the potential to introduce sweet and fruity notes. No synergistic effects were observed with ultrasonic treatment. Taken together, fermentation represents a clean-label approach to modifying YP for food applications like dairy alternatives requiring high solubility, WHC, and emulsification.