EFFECT OF FATTY-ACID POSITIONAL DISTRIBUTION AND TRIACYLGLYCEROL COMPOSITION ON LIPID BY-PRODUCTS FORMATION DURING HEAT-TREATMENT - I - POLYMER FORMATION

Effects of the fatty acid positional distribution and of the triacylgl ycerol (TC) composition on polymerization of TC during heat treatment were studied. Diacid TG molecules, acylated only with linoleic acid or linolenic acid along with palmitic acid, and positioned either in the central position (PLP acid PLnP, respectively) or in one of the two o uter positions (PPL and PPLn, respectively) were synthesized. Monoacid TG, i.e., trilinolein and trilinolenin, were also synthesized and mix ed with tripalmitin in a 1:2 ratio. These model TC were also compared to TC models that consisted of a canola oil and its randomized counter part, whose fatty acid positional distribution and TC composition were determined by means of high-performance liquid chromatography (HPLC). After heating, the polymer content and composition were evaluated by HPLC-size exclusion chromatography. Both pure TC and the canola oil mo dels showed that acylation of polyunsaturated acids in the central pos ition was protective against polymerization, although the effect was m ainly observed with linolenic acid. The synthetic-TG study showed that the monoacid TG species exhibited higher sensitivity toward polymeriz ation than the diacid species. The slight differences in the TC specie s between both canola oils did not allow observation of such a relatio nship with regard to TC composition.