Synchrotron Radiation
Macrobeam and Microbeam X-ray
Diffraction Studies of Interfacial Crystallization of Fats in Water-in-Oil
Emulsions
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Abstract
Using macrobeam and microbeam techniques, we performed
synchrotron
radiation X-ray diffraction (SR-XRD) analyses of fat crystallization
in water-in-oil (W/O) emulsion, in combination with DSC and polarized
optical microscopic observation. Particular focus was on the crystallization
of the fats around water droplets in the W/O emulsion systems using
food emulsifiers of polyglycerol polyricinoleate (PGPR) alone (PGPR
emulsion), and PGPR and monobehenoylglycerol (MB) (PGPR+MB emulsion).
We obtained the following results: (1) macrobeam SR-XRD confirmed
that adding MB promoted fat crystallization during cooling, (2) microbeam
SR-XRD indicated that the lamellar planes of fat crystals near the
water and oil interfaces are arranged almost parallel to the interface
planes in both PGPR emulsion and PGPR+MB emulsion, and (3) adding
MB resulted in the formation of tiny fat crystals because it promoted
crystallization, which occurred both in the bulk oil phase and at
the W/O interfaces. The present study is the first to apply microbeam
SR-XRD to observe the microscopic features of fat crystallization
in W/O emulsion, following fat crystallization in the oil droplets
in the oil-in-water (O/W) emulsion (Arima, S.; Ueno, S.; Ogawa, A.;
Sato, K. <i>Langmuir</i> <b>2009</b>, <i>25</i>, 9777–9784)