Abstract
Fat crystallization in oil-in-water (O/W) emulsion is one of the major factors of destabilization phenomena of O/W emulsion through partial coalescence. Partial coalescence causes serious deterioration of O/W emulsion that is used in many food products, such as whipped cream. In this study, we found that stability of the O/W emulsion containing palm-mid-fraction (PMF) was improved by using hydrophobic and hydrophilic sucrose fatty acid esters with high-melting point fatty acid moieties as additives. Emulsion without additives showed gelation occurring at chilled temperatures from 60°C to 0°C by partial coalescence of oil droplets through the crystallization of PMF. Furthermore, the oil and water phases were separated after heating the chilled emulsion to 60°C (oil-water separation). However, when hydrophobic and hydrophilic sucrose fatty acid esters were added in the oil and aqueous phase, respectively, gelation at 0°C was remarkably retarded and the oil-water separation after re-heating did not occur. The differential scanning calorimetry (DSC), polarized optical microscopy and X-ray diffraction analyses indicated that the inhibition of destabilization was caused by promotion of the crystal nucleus formation by a template effect of the hydrophobic additive, limitation of a crystal growth direction, reinforcement of the emulsification membrane by the hydrophilic additive, and retardation of the transformation of an α to β′ form of the PMF crystals in the oil droplets.
