Improved emulsification behaviour of acid-soluble pea proteins in the development of acidic beverage emulsions

Abstract: Plant-based proteins, especially pea proteins, have recently attracted increasing attention as food emulsifiers. However, likewise other plant proteins, pea proteins are intractable due to poor aqueous solubility and sensitivity to environmental conditions, which limit their applications. Therefore, finding a way to improve their functionality is highly sought after. Our aim was to recover the acid-soluble fraction of pea proteins using simple centrifugation and utilize the acid-soluble pea proteins (ASPP) for stabilizing oil-in-water emulsions at acidic pH, which is appropriate for sports beverage applications. It was hypothesized that ASPP would provide a better emulsifying property due to their higher solubility at acidic conditions, which is suitable for beverage applications. Thus, ASPP was extracted from a pH 2 dispersion of 7 wt% pea protein concentrate (PPC) by centrifuging and separating the supernatant aqueous phase. The ASPP, containing 2.5 wt% protein, was directly used to prepare 5 wt% canola oil-in-water (O/W) emulsions. The physical stability of the emulsion was determined during 28 days of storage and against environmental stress conditions. The O/W emulsion was physically stable during storage with a slight increase in surface average droplet size from 163 nm to 227 nm. The creaming velocity, also increased from 21.5 to 29.0 µm/min after 28 days. The O/W emulsion had good stability against heat treatment at 90ºC for 30 min and low salt concentrations (0.1M NaCl), which could be due to the pre-exposure of hydrophobic patches of ASPP at pH 2 before emulsification, confirmed by surface hydrophobicity and intrinsic fluorescent measurements. At higher salt concentrations (0.5 and 1M) droplet size increased and creaming velocity increased from 21.54 to 50.82 µm/min from 0 to 1 M NaCl. Our study offers straightforward new means to improve pea proteins functionality by designing alternative fractionation routes for targeted techno-functionalities to facilitate their usage in acidic beverages.