Effect of emulsifier-fat interactions and interfacial competitive adsorption of emulsifiers with proteins on fat crystallization and stability of whipped-frozen emulsions

Fat crystals and adsorbed interfacial layer are very important in controlling the stability of partly crystalline fat globules. In this study, the effects of competitive adsorption of emulsifiers, including glyceryl monooleate (GMO) and sucrose ester (SE) with milk proteins and emulsifier-fat (anhydrous milk fat, AMF; coconut oil, CO) interactions on the fat crystallization behavior and stability of whipped-frozen emulsions were investigated. Parameters such as zeta potential, surface protein coverage, rheological property, fat crystallization behavior, overrun, melting rate and microstructure of ice cream were determined. The results indicated both GMO and SE affected the crystallization behavior, changing the crystal growth, morphology and stiffness. Different mechanism was involved in fat partial coalescence in emulsion systems with different fat-emulsifier interactions. The promotion of partial coalescence in whipped-frozen emulsions with increasing concentration of GMO was mainly related to fat crystallization behavior combined with increased fat crystal growth dimension and protrusion length at the fat globule surface, since protein surface coverage was not affected by GMO concentration. However, in the case of emulsions with SE, enhancement of partial coalescence was mainly related to decreased protein surface coverage combined with less resistance of interfacial membranes to penetration by small fat crystals. Ice cream based on CO were distinguished by higher overruns and lower melting rates compared to ice cream based on AMF with the same levels of emulsifiers, especially strong fat crystal network in the presence of GMO accounts for the increased air bubble stability. These findings provides a theoretical basis for aerated food processing.