Exploring the oil-water interfacial behaviour of pea protein-guar gum/gellan gum mixtures relating to stability and in vitro protein digestion of model pea milk system

Polysaccharides are effective stabilisers for plant-based milks, but their interfacial adsorption behaviours in plant milk system and effects on plant protein digestibility are still unclear. This study analysed the oil-water interfacial adsorption behaviours of pea protein concentrate (PPC) and isolate (PPI) mixed with neutral guar gum and anionic gellan gum to understand the stability and in vitro protein digestion of corresponding model pea milk system. Adding guar gum or gellan gum enhanced the interfacial adsorption stability of pea proteins without compromising proteolysis during gastrointestinal digestion. Gellan gum performed better than guar gum for long-term co-stabilising the emulsion with pea proteins, due to its electrostatic repulsion with pea proteins and stronger steric hindrance induced by thicker adsorbed interfacial layers (~10 % or ~37 % higher thickness than guar gum counterparts) as detected by a quartz crystal microbalance with dissipation (QCM-D) after rinsing. The model pea milks with 0.1 % (wt%) gellan gum were stable at 4 °C for 28 days regardless of protein types. The presence of polysaccharides at the interface enabled oil droplets to be kept separate during in vitro gastrointestinal digestion, improving the final proteolysis by ~4 to ~27 %. This result is conducive to selecting polysaccharides for developing pea protein-based beverages.