Abstract
Lard and edible tallow were subjected to a series of fractional crystallizations from acetone at temperatures from 20° to -45°C. Six recrystallized precipitate fractions and a filtrate residue were obtained from each fat. In addition to determining the more common physical and chemical characteristics, fatty acid composition of each fraction was calculated from spectrophotometric data, iodine value, and thiocyanogen value. The consistent results obtained throughout by the spectrophotometric method of fatty acid analysis lend further confirmation to the reliability of this method for composition studies of natural fats. The approximate amounts of tri-saturated, di-saturated, mono-saturated, and tri-unsaturated glycerides of the lard and tallow were estimated from the analysis of each fraction on the assumption that not more than two of these classes of glycerides were present in any one fraction. The tallow contains much higher proportions of tri-saturated and di-saturated glycerides and correspondingly lower proportions of the mono-saturated and tri-unsaturated glycerides than does lard. The amount of tri-unsaturated glycerides in lard was found to be significantly greater than meager information in the literature would indicate. The data indicate that the general pattern of glyceride formation in animals such as the pig and cow is probably of random character.
Published Version
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