Laboratory separation of crystals from plastic fats using detergent solution

An improved laboratory technique for isolating the solid-fat fraction from plastic fats is described. The fat first is dispersed in an aqueous detergent solution; then the oil and solid fat fractions are separated by high speed centrifugation. To facilitate the separation, a 25% ammonia solution is added to adjust the density of the water phase to between those of the oil and the solid-fat phase. After rinsing with cold ethanol, a solid-fat fraction is obtained-contaminated with only ca. 5% oil-which can directly be used for differential thermal and X-ray analyses. The method also can be applied for a quick determination of the solid-fat content according to the dye dilution principle and for obtaining oil-free fat crystals for electron microscopy.