Countercurrent Distribution of Milk Fat Triglycerides

Abstract

Summary The purpose of this study was to investigate the application of countercurrent distribution to the separation of milk fat triglycerides. Of the solvent systems tested, the most satisfactory was a 12:7:5 mixture of pentane, 2-nitropropane, and nitromethane. The distributions were followed gravimetrically and by determination of iodine values and saponification equivalents of selected fractions or groups of fractions. The fractionation was influenced by degree of unsaturation and molecular weight of the triglycerides. Although useful separations were obtained with 100 stages, better resolution was achieved by applying the technique to samples previously separated from milk fat by crystallization from pentane at low temperatures. The +4° C. precipitate and −53° C. filtrate were fractionated by countercurrent distribution, and the fatty acids in selected fractions were determined by ultraviolet spectrophotometry and gas-liquid chromatography. Evidence was obtained that there is some degree of selectivity of fatty acids during the formation of milk fat. From the analysis of the +4° C. precipitate, the evidence seems clear-cut that a small amount of tripalmitin is present in addition to dipalmitostearin and dipalmitomyristin. In the −53° C. filtrate, the monoethenoid acids are associated with the higher molecular weight saturated acids, whereas the polyethenoid acids are associated with the lower molecular weight saturated acids.