Retardation of crystallization-induced destabilization of PMF-in-water emulsion with emulsifier additives.
An oil-in-water (O/W) emulsion, in which the oil phase is semi-solid fat, is easily destabilized when stored below the crystallization temperature of the oil phase. Such destabilization, characterized by loss of fluidity at chilled temperature and oil-water separation after re-heating, is caused by inter-droplet bridging of fat crystals protruding out of the emulsion droplets. In the present study, we found that the simultaneous use of additives of highly hydrophobic sucrose oligoester (SOE; P-170) and highly hydrophilic SOE (P-1670) containing palmitic acid moiety remarkably retarded the crystallization-induced destabilization of the O/W emulsion that contains palm-mid-fraction (PMF) as the oil phase. Without the additives, destabilization occurred when the emulsion was cooled from 60 to 0 degrees C and kept at 0 degrees C for 1 day. Microscopic observation revealed that destabilization was caused by coalescence of the oil droplets, which was triggered by the growth of needle-shaped PMF crystals protruding out of the emulsion membranes. However, the addition of P-170 to PMF increased the crystallization temperature of PMF and at the same time retarded the destabilization. Furthermore, the simultaneous addition of P-170 and P-1670 retarded the crystallization-induced destabilization even more. Optical observation, DSC, and synchrotron radiation X-ray diffraction measurements indicated that the P-170 additive enhanced interfacial heterogeneous crystallization to form tiny PMF crystals in the droplets, and that the P-1670 additive retarded morphological change of the PMF crystals into long needle shapes in association with polymorphic transformation from alpha to beta'.
Arima
Satoshi
S
Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan.
Ueji
Toshiyuki
T
Ueno
Satoru
S
Ogawa
Akihiro
A
Sato
Kiyotaka
K
D003460:Crystallization; D018360:Crystallography, X-Ray; D004655:Emulsions / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D019308:Palmitic Acid / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
D004655:Emulsions; D004952:Esters; D014867:Water; D019308:Palmitic Acid