Lima bean (Phaseolus lunatus Linn.) protein isolate as a promising plant protein mixed with xanthan gum for stabilizing oil-in-water emulsions

BACKGROUND: Lima bean protein isolate (LPI) is an underutilized plant protein. Similar to other plant proteins, it may display poor emulsification properties. In order to improve its emulsifying properties, one effective approach is using protein and polysaccharide mixtures. This work investigated the structural and emulsifying properties of LPI as well as the development of an LPI/xanthan gum (XG)-stabilized oil-in-water emulsion. RESULTS: The highest protein solubility (84.14%) of LPI was observed and the molecular weights (M-w) of most LPI subunits were less than 35 kDa. The enhanced emulsifying activity index (15.97 m(2) g(-1)) of LPI might be associated with its relatively high protein solubility and more low-M-w subunits (M-w < 35 kDa). The effects of oil volume fraction (phi) on droplet size, microstructure, rheological behavior and stability of emulsions were investigated. As phi increased from 0.2 to 0.8, the emulsion was arranged from spherical and dispersed oil droplets to polyhedral packing of oil droplets adjacent to each other, while the LPI/XG mixtures changed from particles (in the uncrowded interfacial layer) to lamellae (in the crowded interfacial layer). When phi was 0.6, the emulsion was in a transitional state with the coexistence of particles and lamellar structures on the oil droplet surface. The LPI/XG-stabilized emulsions with phi values of 0.6-0.8 showed the highest stability during a 14-day storage period. CONCLUSION: This study developed a promising plant-based protein resource, LPI, and demonstrates potential application of LPI/XG as an emulsifying stabilizer in foods.(c) 2023 Society of Chemical Industry.

Automated summary

The study showed that Lima bean protein isolate (LPI) has high protein solubility and low molecular weight subunits, contributing to its enhanced emulsifying activity index. The microstructure and stability of emulsions vary with different oil volume fractions, with LPI/XG mixtures transitioning from particles to lamellae at higher oil fractions. LPI/XG-stabilized emulsions with oil volume fractions of 0.6-0.8 demonstrated the highest stability during storage.