Effect of fatty acid positional distribution and triacylglycerol composition on lipid by‐products formation during heat treatment: III—Cyclic fatty acid monomers study

Abstract

AbstractThe influence of isomeric triacylglycerols (TG) containing 18:3n‐3 and 18:2n‐6 on the formation of cyclic fatty acid monomers (CFAM) after heat treatment was assessed. Diacid TG, containing linoleic acid (L) or linolenic acid (α‐Ln) along with palmitic acid (P), and positioned either in the central position (PLP and PLnP, respectively), or in one of the two outer positions (PPL and PPLn, respectively) were synthesized. Monoacid TG of trilinolein and trilinolenin mixed with tripalmitin were also prepared. The CFAM formed after heating were analyzed after total hydrogenation. The results obtained with the model TG were compared to another model consisting of a canola oil and its randomized counterpart. In diacid TG, the location of α‐Ln in the central position of the TG molecule (PLnP) greatly enhanced the formation of the CFAM upon heating at temperatures below 240°C. On the other hand, 18:3n‐3 in monoacid TG (LnLnLn) was highly resistant to CFAM formation within the same range of temperatures (180–220°C). The TG structure, more than the TG composition, seemed to explain the differences in the CFAM formation between the original canola oil and its interesterified counterpart. Like α‐Ln, 18:2n‐6 was more prone to cyclization when attached at the central position of the model TG. Conversely, the influence of the TG composition on the cyclization rate was less important for L than for α‐Ln. It was concluded that positioning the C18 polyunsaturated fatty acid in the central position of TG rendered the oils much more sensitive to the cyclization reaction upon heat treatment.