STEADY-STATE FLUORESCENCE POLARIZATION SPECTROSCOPY AS A TOOL TO DETERMINE MICROVISCOSITY AND STRUCTURAL ORDER IN FOOD SYSTEMS

The theory and applications of fluorescence polarization spectroscopy in food research are reviewed in detail with special emphasis on (a) microviscosity determination of isotropic fluids such as edible fats and oils, and oil-in-water emulsion cores using the Perrin equation, and (b) structural order determination of liposomes and biological membranes using infinite-time and limiting anisotropies. Fluorescence polarization is a spectroscopic technique which allows the measurement of the rate of motion and motional orientational restrictions of a fluorescent molecule in solution. By measuring the hydrodynamic properties of a probe in a particular medium, it is possible to determine the microscopic viscosity, while by measuring the orientational restriction of that motion, it is possible to determine the structural 'order' of the medium. This technique provides a powerful tool to the food scientist for the study of the physical properties of foods and food components.