¹³C nuclear magnetic resonance spectroscopy to check 1,3-random, 2-random pattern of fatty acid distribution in olive oil triacylglycerols

Abstract

The fatty acid distribution between the 1,3- and 2-positions of triglycerides was determined in the olive oil set sampled in the Marche region, by using the ¹³C NMR method which applies the DEPT pulse sequence. The results confirmed that the oleic and linoleic acids were not randomly distributed at the 2-position of triacylglycerols but were lower for oleic acid and higher for linoleic acid compared to the theoretical values expected for a random distribution. Moreover, the unsaturated acids deviated from the 2-random distribution at different extents according to the acid concentration of triglyceride.The ¹³C NMR results, they were obtained for three olive oil samples characterized by high, medium and low oleic acid at 2-position (O_found) corresponding to a low, medium, high deviation rate from the 2-random pattern, were compared to those calculated by the computer program based on the 1,3-random-2-random distribution of fatty acids in the triglycerides.The molar concentrations of the triglyceride species LLL and OLL were calculated from the molar concentrations of oleic and linoleic acids at the 2- and 1,3-positions obtained by using ¹³C NMR and the computer method. The LLL and OLL triglycerides determined by the computer method were found to be markedly higher in the “high O_found” oil as compared to NMR. No differences were detected between the two methods for both triglyceride species in the “low O_found” oil.