Detection of adulteration

A program of work is in progress to establish the levels and ranges of fatty acids and other components present in the major edible vegetable oils. Authentic samples from the major producing areas for such oil have been obtained and analyzed. In the case of palm oil, ranges of the fatty acid composition and of the acids at the triglyceride 2-position, have been obtained for about 40 samples. These data were used to calculate enrichment factors, and triglyceride carbon number compositions, using a small computer program. Comparison with experimentally determined carbon number compositions were then made. Good correlations were found for whole unadulterated oils, but not for oil fractions. Unfortunately, these differences were insufficient to detect contamination of palm oil by 10 or 20% levels of other oils, or of palm fractions. Compositional ranges of sterols and tocopherols have also been determined on a selection from the original set of palm samples. Work on sunflower seed and groundnut oils has followed the same lines, particular attention having been paid to linolenic acid and, in the case of groundnut oil, also erucic acid, levels. Some groundnut kernels were found to have an oil with a component which cochromatographed with methyl erucate during fatty acid determination. This unknown constituent was studied by gas chromatography-mass spectrometry, and is thought to comprise a mixture of epoxy fatty acids. Analysis of the triglyceride fraction isolated from groundnut oil by thin layer chromatography removes this unknown constituent, and simplifies interpretation of the fatty acid composition of groundnut oil.