Profile of the Positional Distribution of Fatty Acids in the Triacylglycerols as an Index of Quality for Palm Oil (or Any Oil or Fat)

Abstract

There is a need for a modern method to characterize edible oils and fats. The traditional method is to measure the iodine value (IV), which is an enometric constant that specifies the amount of molecular iodine absorbed by 100 g of the oil/fat. This parameter indicates the degree of unsaturation of the total amount of acylglycerol molecules (mono-, di- and tri-acylglycerols(TAG)) and free fatty acids present in the oil/fat. Variations in the composition of TAG determine the properties of the palm products and hence the quality of the oil/fat. The IV is conventionally used as a quality parameter in the palm oil industry. As an index for characterization the IV has obvious shortcomings or inadequacies. We have shown that the 13C NMR spectrum of the carbonyl carbons of triacylglycerol molecules (TAG) in palm oil in the solution state clearly depicts the positional distribution of the fatty acids (FA). However it is noted that NMR spectroscopy, because of its long timescale, cannot distinguish between the various TAG molecules. In addition, the 13C NMR spectrum cannot distinguish between the saturated FA of similar chain length. The positional distribution profile of fatty acids for an oil/fat permits an assessment for food applications and the nutritional benefits. Hence the positional distribution profile of the fatty acids in the triacylglycerols can be a useful index of quality for the oil/fat.