Cooling-driven polymorphic transition of lipid crystal particles enhancing interfacial rheology and foaming stability...

Pickering fat globules (PFGs) show great potential in food emulsion foam systems due to their excellent foam-stabilizing properties. This study systematically investigated the whipping and aeration characteristics of PFGs formed by surface-active lipid crystal particles derived from glycerol stearate citrate (named as G-crystals) encapsulating liquid soybean oil. G-crystals with varied structures were prepared under controlled fast or slow cooling mode and storage at room temperature for 1 or 4 days, which were named as GF-1d-crystals, GF-4d-crystals, GS-1d-crystals, GS-4d-crystals. Systematic characterization revealed that four G-crystals consisted predominantly of α and β polymorphs. Fast cooled crystal particles (named as GF-crystals) showed lower β polymorph content, better dispersion, and higher hydrophilicity, resulting in a weaker viscoelastic interfacial film at oil-water interface. Slowly cooled samples (named as GS-crystals) exhibited higher β polymorph content, greater aggregation tendency, and stronger hydrophobicity, which contributed to more effective oil-water interfacial tension reduction and formation of a more viscoelastic interfacial film. Extended storage promoted the α to β polymorphic transition, intensifying the above trends. High pressure homogenization during PFG preparation further induced α to β conversion, so that PFGs contained higher β fractions than their precursor crystals. GF-crystals stabilized PFGs (named as GF-PFGs) were characterized by lower β content, higher ζ-potential, smaller contact angles and lower apparent viscosity. GF-PFGs packed loosely at the air-water interface, formed weak interfacial films and yielded poor foam stability. By contrast, GS-crystals stabilized PFGs (named as GS-PFGs), notably GS-4d-PFGs, were β-enriched, prone to aggregation, exhibited lower ζ-potential and higher apparent viscosity, more effectively reduced air-water interfacial tension, packed densely to form highly viscoelastic interfacial films and built three-dimensional bulk networks, thereby delivering superior foaming capacity and foam stability.