Developing thermally stable beverage emulsions using mildly fractionated pea proteins

Abstract

Oil-in-water emulsions are widely used as the base flavoring or clouding agents in various beverages. Pulse proteins can play a major role as a natural emulsifier in beverages. However, the presence of insoluble components greatly minimizes their potential application in beverage emulsions. In this work, pea protein concentrate was mildly fractionated by aqueous centrifugation to recover a soluble fraction with 71% protein yield, which was then used to develop 5% oil-in-water emulsions using a high-pressure homogenizer. Emulsion stability was tested by heat treatment (90°C, 30 min) in the presence of NaCl (0–1 M) at pH 7.0 and 2.0. Stability increased upon the addition of salt at pH 7, while at pH 2, proteins and droplets aggregated. Heat treatment led to extensive aggregation at both pH values, which was further worsened by salt. To prevent thermal destabilization, the proteins were heat-treated at 75°C for 30 min for partial denaturation before emulsification under hot conditions. The heat-treated protein-stabilized emulsions at pH 7 had superior thermal stability at all salt concentrations without aggregation. However, a similar improvement was not observed at pH 2. Pre-heating the soluble protein exposed the hydrophobic patches, leading to better adsorption on the droplet surface, which did not show additional aggregation upon further heating the emulsions at pH 7. Interestingly, heat-treated protein-stabilized emulsions showed a 44% drop in lipid digestibility compared to the original emulsions. The proposed approach could be a valuable addition to the utilization of pea proteins in beverage emulsions that could withstand heat treatment during food processing.