DETERMINATION OF WATER DROPLET SIZE IN MARGARINES AND LOW-CALORIE SPREADS BY NUCLEAR-MAGNETIC-RESONANCE SELF-DIFFUSION

The nuclear magnetic resonance self-diffusion technique can be used to determine the size of emulsion droplets. In this communication, the method is discussed and applied to some margarines and low-calorie spreads, ranging in fat content from 40 to 80%. The data show that the droplet size distribution is fairly polydisperse, at least for the solid margarines studied. A liquid margarine, containing 80% fat and studied by optical microscopy, showed that a log normal size distribution function is a reasonable description of its size polydispersity. Therefore, this distribution function was used in the present work, and the parameters of the log-normal function were determined by a least-square fit directly on the experimental raw data for all the systems studied. The uncertainties in the obtained parameters are judged by means of a Monte Carlo technique. The uncertainty is around +/-15% (or better), Finally, we discuss the possibility of the presence of nonspherical droplets and how the presence of such droplets would actually affect the measurements.