Effects of emulsifiers on vegetable-fat based aerated emulsions with interfacial rheological contributions

Abstract A relationship between oil/water interfacial properties and the whipping performance of vegetable-fat based o/w emulsions was investigated for two emulsifier mixtures: lactic acid esters of mono and diglycerides (LACTEM), and partially unsaturated/saturated monoglyceride mixture (PUS/SMG). The whipping emulsions were evaluated on storage viscosity, overrun, and firmness. The model interfacial layer between water and oil with LACTEM gave higher shear modulus and the emulsion showed low bulk viscosity, high overrun and high firmness after whipping. The interfacial modulus with PUS/SMG was lower and the emulsion provided higher bulk viscosity, lower overrun and lower firmness. Microscopy and particle size distribution in sheared unwhipped emulsions showed individual fat globules without aggregation in the case with LACTEM, while globules with PUS/SMG became highly aggregated. These suggest that the weaker interfacial layer with PUS/SMG can be more susceptible to the fat crystal mediated partial coalescence of fat globules: Partial coalescence can happen already during quiescent storage. The subsequent whipping led to further aggregation then a strong fat network can help to stabilize air bubbles. The more stable interfacial layer in LACTEM-based emulsions leads to a lower tendency to coalesce during quiescent conditions, and only to aggregation and coalescence during the whipping stage. Fat aggregation was confirmed to be essential in achieving a good aerated structure but there were differences depending on the surface layer properties of fat globules induced by emulsifiers. This caused the rheological differences observed during storage.