Preparation and Fractionation of the High Melting Glyceride Fraction of Milk Fat

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Abstract
High melting glyeeride (HMG) was prepared from anhydrous milk fat and from a commercially prepared hard frac- tion of a different milk fat. The latter glyceride was further fractionated by progressive crystallization from acetone. The first precipitation of HMG reduced the softening point of the supernatant fat to about 18 C, primarily by elimi- nating fats melting above 20 C. The melting properties of the supernatant to the recn/stallization of HMG depended upon the source of fat. That from anhy- drous milk fat had a limited melting range whereas that from the hard frac- tion had an extended melting range. Thermograms of the glyceride prepara- tions indicated the possible existence of co-crystallization in both quickly cooled and tempered samples. Five fractions were prepared from HMG by progressive crystallization from acetone. The three highest melting fractious had thermo- grams typical of pure solid phases. All samples of HMG or its fractions could be cu, stallized unstably by rapid cooling of the melt. Two types of transitions were detected on the thermograms of samples in an unstable form, a direct transition between the unstable and stable forms and a melting of the un- stable form followed by re-crystallization into the stable form. The melting points of the stable forms of the HMG frac- tions varied from 27 C to 56 C, whereas the intact HMG melted at 46 to 49 C. The saturated fatty acid residues of the HMG fractions varied from 97% (mole) for the highest melting to 77% for the lowest melting.