In vitro digestibility study of thermal oxidized palm oleins

information on digestibility and absorption of oils and fats used for fryin g is under debate. To get knowledge on this, unused palm olein (9.27 +/- 0. 10% w/w polar content), used frying palm olein with a moderate degree of al teration (14.81 +/- 0.90% w/w polar content) and highly altered used frying palm olein (26.36 +/- 0.30% w/w polar content) and their respective nonpol ar and polar fractions were studied. Samples were analyzed by high-performa nce size-exclusion chromatography before and after a 20-min in vitro incuba tion with pancreatic lipase. Formation of monoacylglycerols and free fatty acids reflected no relevant differences between unused and moderately alter ed oleins, whereas the most altered olein was hydrolyzed to a much lesser d egree. The presence of oligomers (dimers and polymers of triacylglycerols) negatively affected the hydrolysis of triacylglycerol monomers in whole ole ins. The hydrolysis of these monomers in the isolated nonpolar and polar fr actions ranked between 60.2% and 78.5%. Oligomers were efficiently hydrolyz ed by pancreatic lipase in whole unused and moderately altered oleins but n ot in the most altered one. Polymers from isolated polar fractions were poo rly hydrolyzed or not hydrolyzed at all. These data suggest that whole olei ns contained some compounds that increase susceptibility of oligomers to en zymatic hydrolysis and that such compounds were not present in the polar fr action.