Enzymatic hydrolysis of fractionated products from oils thermally oxidized in the laboratory

Abstract

Enzymatic hydrolysis of the acylglycerol products obtained from thermally oxidized vegetable oils was studied. Corn, sunflower and soybean oils were heated in the laboratory at 180 C for 50, 70 and 100 hr with aeration and directly fractionated by silicic acid column chromatography. By successive elution with 20%, then 60% isopropyl ether in n-hexane, and diethyl ether, the thermally oxidized oils were separated into three fractions: the nonpolar fraction (monomeric compounds), slightly polar fraction (dimeric compounds), and polar fraction comprising oligomeric compounds. Enzymatic hydrolysis with pancreatic lipase showed that the monomers were hydrolyzed as rapidly as the corresponding unheated oils, the dimers much more slowly, and the oligomeric compounds barely at all. Overall, the hydrolysis of the dimers was less than 23% of that for the monomers, with small differences among the oils. Longer heating periods resulted in greater reductions in hydrolysis of the dimeric compounds. These results suggest that the degree of enzymatic hydrolysis of the fractionated acylglycerol compounds is related to differences in the thermal oxidative deterioration, and amounts of polar compounds in the products.

Column and high‐performance size exclusion chromatography applications to the in vivo digestibility study of a thermoxidized and polymerized olive oil

“…In fact the polar fraction of the olive oil increased about 13 times after the heating treatment. This increase is agreement with previous data published in frying oil (21)(22)(23)(24)(25) and heated oils (19,26).…”

“…According to Yoshida and Alexander (26), two typical groups of products-volatile breakdown derivatives and nonvolatile oxidation products-are produced by oil heating. The latter products include monomeric, dimeric, and polymeric compounds.…”

Short‐term in vivo digestibility assessment of a highly oxidized and polymerized sunflower oil

“…16,17 Nevertheless, the true digestibility of the heated sunflower oil (410 ± 34 g kg −1 ) found in the current study (Fig 1) tended to be higher than that found previously for heated olive oil (354 ± 68 g kg −1 ). 16 These data suggest that, although some compounds of the heated sunflower oil are resistant to pancreatic lipase or induce inhibition of enzyme lipases, 27,28 there are some compounds in this oil that improve the action of lipase in comparison with olive oil. Some time ago our group suggested that the in vitro digestion of palm olein and other oils improved when the surfactant concentration in the oil produced during frying increases.…”

Changes in enzymic hydrolysis in vitro of thermoxidised canola oil

“…Fractions I, 11,111 and IV consisted of acylglycerol monomers, dimers, trimers and polymers, respectively (Yoshida and Alexander 1983). The acylglycerol monomers decreased substantially with heating, and these values were compensated for by increases of more polar materials.…”