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

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.