Effect of intramolecular fatty acid distribution on aspects of triacylglycerol digestion and absorption studied in vitro.

The triacylglycerols from several natural sources have been used as substrates for in vitro assays of three different aspects of fat digestion and absorption. The triacylglycerol mixtures were chosen because they differed widely both in total fatty acid composition and in the intramolecular distribution of fatty acids. The assays were designed to test the rate of hydrolysis with pancreatic lipase, the ability to form insoluble calcium soaps during the hydrolysis, and the ability to form mixed micelles with bile during the hydrolysis. Differences in the rate of hydrolysis appeared to be related to the structure and the triacylglycerols from lard and human milk, both of which have palmitic acid esterified in the sn-2 position, were hydrolysed most rapidly. Similarly the ability to form calcium soaps was related to structure and those triacylglycerols which released saturated fatty acids on hydrolysis favoured calcium soap formation. While there was a range of abilities to form mixed micelles with bile no obvious correlation with structure was detected.