Hypothesis Interfacial adsorption rate of emulsifiers governs droplet coalescence during emulsification. These fast dynamic processes remain poorly understood for plant proteins, especially under practical conditions such as heating. We hypothesize that moderate preheating (below denaturation temperature) on the potato protein (POPI) enhances adsorption through increased hydrophobic exposure, while excessive heating leads to aggregation that decreases interfacial film strength, with these mechanisms governing early-time droplet stability. Experiments The effect of protein concentration and preheating temperature (20–95 °C) on the short-time interfacial behavior of POPI was investigated. Protein adsorption at the oil-water interface and droplet re-coalescence were determined at millisecond timescales using two microfluidic devices: the Edge-based Droplet GEneration (EDGE) tensiometer and the coalescence cell. Findings POPI (2 wt%) adsorbed rapidly at the oil-water interface (~27 ms to decrease from the initial bare interfacial tension value). Preheating POPI at temperatures below its denaturation temperature ( T d ~ 65 °C) sped up initial adsorption. When preheating at 70 °C, protein initial adsorption slowed down due to aggregation that delayed diffusion. However, at 95 °C, adsorption increased again, possibly because of further exposure of hydrophobic residues that enhanced interfacial affinity. Despite changes in adsorption rate, heating generally increased droplet coalescence. This indicates that interfacial properties rather than adsorption rate alone, control early-time stability. Furthermore, increasing protein concentration compensated for heat-induced functionality loss. These results reveal how heat-induced protein changes govern its interfacial adsorption and stabilization at short timescales, providing new insights relevant to the design of stable (plant) protein-stabilized emulsions.
Cao et al. (2026) studied this question.