pH-Controlled Yeast Protein Precipitation from Saccharomyces cerevisiae: Acid-Induced Denaturation for Improved Emulsion Stability

In the search for alternative protein sources, single cell proteins have gained increasing
attention in recent years. Among them, proteins derived from yeast represent a promis-
ing but still underexplored option. To enable their application in food product design,
their techno-functional properties must be understood. In order to investigate the im-
pact of precipitation pH on their emulsion-stabilizing properties, yeast proteins from
Saccharomyces cerevisiae were isolated via precipitation at different pH (pH 3.5 to 5) after
cell disruption in the high-pressure homogenizer. Emulsions containing 5 wt% oil and
~1 wt% protein were analyzed for stability based on their droplet size distribution. Proteins
precipitated at pH 3.5 stabilized the smallest oil droplets and prevented partitioning of the
emulsion, outperforming proteins precipitated at higher pH values. It is hypothesized that
precipitation under acidic conditions induces protein denaturation and thereby exposes
hydrophobic regions that enhance adsorption at the oil–water interface and the stabilization
of the dispersed oil phase. To investigate the stabilization mechanism, the molecular weight
... mehr
of the proteins was determined using SDS-PAGE, their solubility using Bradford assay,
and their aggregation behavior using static laser scattering. Proteins precipitated at pH 3.5
possessed larger molecular weights, lower solubility, and a strong tendency to aggregate.
Overall, the findings highlight the potential of yeast-derived proteins as bio-surfactants and
suggest that pH-controlled precipitation can tailor their functionality in food formulations.