On the stability of acid-soluble pea protein-stabilized beverage emulsions against salt addition and heat treatment

Abstract

This study explores the use of an acidic water-soluble fraction of pea protein as an effective plant-based emulsifier for stabilizing low-pH oil-in-water emulsions. Mildly fractionated soluble pea protein (containing 2.5 wt% protein), recovered by centrifuging pea protein concentrate dispersion at pH 2.0, was directly used to prepare a 5 wt% canola oil-in-water emulsion using a high-pressure homogenizer. Emulsion stability was evaluated at pH 2.0 for 28 days at room temperature as well as against environmental stress conditions, including heat treatment (90 °C, 30 min) in the presence and absence of NaCl (0–1 M). The results showed that the acidic water-soluble pea protein, rich in albumins, exhibited excellent emulsifying properties and improved thermal stability, showing minor changes in droplet size until day 28, even after heat treatment. We proposed that such improved emulsion thermal stability under acidic conditions could be due to the high albumin content, lower surface hydrophobicity and higher β-sheet and random coil secondary structure content of the acidic-soluble fraction compared to the whole pea protein pH 7.0 extracts. However, the emulsions were unstable against high salt concentrations (0.5 and 1 M NaCl), showing extensive aggregation worsened by heating, which was attributed to the charge screening effect of salt and unfavourable conformational change in the albumin-rich proteins. The novel findings of this study can provide essential knowledge and set the stage for the development of pea protein ingredients ideal for utilization in ready-to-drink acidic plant-based beverages.