Influence of the position of unsaturated fatty acid esterified glycerol on the oxidation rate of triglyceride

Abstract

The influence of the position of unsaturated fatty acid esterified glycerol on the oxidation rate of triglyceride was investigated at 50 C. Randomized triglycerides used were prepared by random interesterification between saturated and unsaturated monoacid triglycerides using Sodium methoxide as catalyst. The monoacid triglycerides used were tripalmitin, tristearin, triolein and trilinolein. The molecular species of the randomized triglycerides were analyzed by high performance liquid chromatography (HPLC) in combination with gas liquid chromatography (GLC) and enzymatic hydrolysis. From the results of oxygen absorption measurement by GLC, the randomized triglycerides were more stable towards oxidation than the triglyceride mixtures which were prepared by mixing the equivalent quantities of the same monoacid triglycerides as used in the random interesterification. This may be due to the decrease in the contents of most unstable unsaturated monoacid triglycerides by random interesterification with saturated monoacid triglycerides. Furthermore, from the results obtained with the detailed analysis of the randomized triglycerides at different stages of oxidation, it became clear that the triglycerides having unsaturated fatty acids linked at the 2-position of glycerol are more stable towards oxidation than those linked at the l(or 3)-position. The carbon chain length of saturated fatty acids has essentially no influence on the oxidation rates of unsaturated fatty acids esterified in the same glycerol.

Comparison of the oxidative stability of chemically and enzymatically interesterified fats

“…2). It facilitated easier access of oxygen to these acids causing, and thus, according to theoretical expectations, their easier oxidation [12,14].…”

“…The distinctive differences in the amount of this phase are also observed between pure triacylglycerols isolated from both interesterification products. Apparently, the oxidative stability of fatty product depends primarily on the composition of fatty acids, on the structure of triacylglycerols, and especially on the position of polyenic acids, which are susceptible to oxidation [14]. This stability also depends on the amount and nature of non-TAG components, particularly on the amount of tocopherols [26].…”

“…the resistance of fats to oxidation, is determined by the structure of triacylglycerols [12,13], and particularly by the position of polyenic fatty acids, which are especially susceptible to oxidation. The larger the percentage of these acids in the external positions of triacylglycerols, the easier is the access of oxygen to these acids and hence the smaller is the oxidative stability of a fat [14].…”

Effects of Triacylglycerol Molecular Species on the Oxidation Behavior of Oils Containing α-Linolenic Acid

“…This result was also supported by heating oxidation tests (180℃, 7 h) using the interesterified blended oils; the residual ratio of Ln-TAGs in the oils was found to be in the order of 3Ln-TAG＜2Ln-TAG＜1Ln-TAG. Oxidation stability of Lipase OF ed fatty acids at the sn-2 position was greater than those having fatty acids at the sn-1 3 position, as determined by comparison of the oxidation rates of interesterified TAGs prepared from tripalmitin, tristearin, triolein, and trilinolein 4 . Marine oils such as whale, sardine, cod liver, and skipjack oils were subjected to Lipase TOYO ® mediated interesterification, and all, except whale oil, had higher oxidation stabilities after interesterification: this is due to the reduction in the content of highly unsaturated TAG that occurs on interesterification 5 In this study, we first prepared interesterified oils from perilla oil -Egoma yu in Japanese -and its blended oil with palm oil using either the sn-1,3 positional specific Lipozyme RM-IM ® or non-specific Lipase OF ® to obtain oils having the same fatty acid composition but with different compositions of TAG species.…”

Changes in chemical composition of rapeseed meal during storage, influencing nutritional value of its protein and lipid fractions

“…At the 1(or 3) -positions the oleic acid and SFA are linked. However, there are conflicting results of studies on the influence of the position of UFA esterified with glycerol on the oxidation rate (Wada and Koizumi, 1983;Neff and El-Agaimy, 1996). Another possible cause may also be selective towards PUFA inhibiting acting of water, similar to that occurring in emulsions of the type 'oil in water' (Miyashita, 2008).…”