Modeling of the Triacylglycerol Stereospecific Composition of Vegetable Oils: I. Comparison of Models for Triacylglycerol Assembly

Stereospecific composition of triacylglycerols (TAGs) is calculated for a set of analytical data on genetically modified sunflower and soybean seed oils, using different mathematical models for TAG assembly. The models are related to biochemical pathways. The data (Reske et al., JAOCS 74 (1997) 989-998) consist of total fatty acid profiles, fatty acid proportion in the sn-positions of TAGs, and TAG composition determined by HPLC analysis without distinguishing isomers. Besides the 1-random, 2-random, 3-random models, a DAG-random, 3-random model is examined, the parameters of which are estimates of mole fractions of sn-1,2-diacylglycerols (sn-1,2-DAGs) before esterification at the sn-3 position. Combining the last named model with correlations of fatty acid proportions in the sn-positions and overall fatty acid composition, triacylglycerol stereospecific composition can be estimated from the TAG composition determined by HPLC. The deviation of the estimates from analytical characteristics of oils (fatty acid distribution and TAG composition) is less than the deviation of results of the Vander Wal model. Practical Applications: It can be expected that the DAG-random, 3-random model with arbitrarily adjustable distribution of acyls in sn-1,2-diacylglycerols can reflect the composition of TAGs rich in polyunsaturated fatty acids better than previously used models. The reason is that it can reflect acyl editing in phosphatidylcholine pool of seed cells, while the 1-random, 2-random, 3-random models correspond to simple Kennedy pathway of oil biosynthesis.

Automated summary

The stereospecific composition of triacylglycerols (TAGs) in genetically modified sunflower and soybean seed oils was calculated using various mathematical models, with the DAG-random, 3-random model showing potential to better reflect the composition of TAGs rich in polyunsaturated fatty acids. This model considers acyl editing in the phosphatidylcholine pool of seed cells, unlike simpler models that correspond to the Kennedy pathway of oil biosynthesis.