Interfacial compositions of fat globules modulate coconut oil crystallization behavior and stability of whipped-frozen emulsions

Abstract

Interfacial compositions and fat crystals are of importance for determining the partially crystalline fat globule stability. The objective of this work was to investigate the effects of different whey-to-milk protein ratios and sucrose fatty acid ester (SE) addition on the coconut oil crystallization behavior and whipped-frozen emulsion stability. Surface protein load shifted to lower values with increasing whey-to-milk protein ratio. Yet, protein-protein interactions and droplet flocculation were enhanced by pasteurization and/or homogenization in emulsions with additional WPC, which hindered displacement of proteins by SE. Formation of small fat crystals were favored by increase in whey-to-milk protein ratios, although fat nucleation and crystal growth were depressed in the absence of SE. The presence of SE facilitated formation of smaller fat crystals and dense crystal network compared with emulsions without SE at the same protein composition. Small amplitude oscillatory deformation experiments revealed increased whey protein addition enhanced the stiffness of crystal network, although the crystalline fat content reduced. The whipped-frozen emulsions containing SE were distinguished by higher partial coalescence degrees (19.52%–254.51%) compared to corresponding emulsions without SE (12.82%–41.67%). The maximum partial coalescence degree was elicited at whey-to-milk protein ratio of 7:3 with SE which was ascribed to a weak adsorbed layer and increase of crystal growth dimensions combined with stiff crystal network. Correlation analysis evidenced enhancement of fat flocculation and partial coalescence accounted for increased overrun and meltdown stability of ice cream, respectively. Findings from this work are helpful to illustrate mechanism behind the stability of aerated emulsions.