3. Fatty acid indices and composition of oils and fats

The characterization of oils and fats has a long history. For animal fats, Chevreul introduced a first characteristic in , "titre", which is the solidification point of fatty acids obtained by saponification of fats followed by acidification of soaps. Later, fats were characterized by the saponification index (SI), which gives information on the average relative molar mass of the fat, and by the iodine index (II), which gives information on the presence of double bonds. Before the advent of gas chromatography (GC), determining the acid composition of a fat was tedious. However, now that this technique is available, it is possible to calculate IS and II indexes from...