Synergistic adsorption of surface-active components at the air-liquid interface improves foaming properties of plant-based egg analogues

Foaming is an important functionality of eggs in aerated food products. However, plant proteins, the main components of plant-based egg analogues, are generally inferior in foaming compared to egg proteins. Hence, this study aimed to elucidate the foaming mechanisms in plant-based egg analogues modified by different amounts of hydroxypropyl methylcellulose (HPMC). The molecular adsorption at the air-liquid interface (ALI) with the mass transfer coefficients (k) was determined by a two-film theory. Plant-based egg analogue with 1.5% HPMC addition matched the foaming capacity (231% vs. 227%) and foaming stability (72% vs. 73%) of liquid egg, due to the thermodynamic incompatibility between biomacromolecules in the vicinity of the ALI that accelerated the protein and lipid adsorption through depletion mechanism (23.2 and 22.7 to-67.8 gm/min for kprotein and klipid, respectively). This led to the highest volumetric synergy, consistency, and elasticity in the foams made thereof. Foams containing less HPMC did not have fast molecular adsorption, probably due to less HPMC on inducing synergistic adsorption. Foams contained more HPMC exhibited HPMC-dominated ALI, competing with protein and lipid adsorption, and reducing foaming properties. It is concluded that HPMC imparts dose-dependent effect on the molecular adsorption at the ALI, which determines the foaming properties of the plant-based egg analogues. Furthermore, this study showed that plant-based egg analogue modified with 1.5% HPMC was promising in sponge cake and omelet production. Accordingly, a series of composite eggless systems based on foaming characteristics can be developed by adjusting the additive amount of HPMC according to actual needs.