Interesterification. I. Change of glyceride composition during the course of interesterification

Abstract

Changes in composition produced in monounsaturated triglycerides during the course of interesterification, before full randomization is achieved, have been followed by using thin-layer chromatography. Results indicate that intraesterification, in which interchanges take place between positions on the same molecule, occurs at a faster rate than the general randomization which results from intcresterification.The reaction is found to proceed according to the expression log a a t, where 'a' is the proportion of fatty acid components not changed in position by the reaction. This expression is of general application to triglyeeridc interesterifications and provides a basic equation in terms of which the effects of temperature, catalysts, and other ex-I)eriInental eon(litions can be studied.

The base‐catalyzed, low‐temperature interesterification mechanism revisited

“…20 min). A similar degree of rate increase was observed when acetone was replaced by fully deuterated acetone-d 6 (Fig. 10D).…”

“…Such chelation is well known in the case of crown ethers or polyethyleneglycol in apolar aprotic media. Although this effect could in principle stabilize a diacylglycerolate anion to a greater extent than linear alcoholates, our experiments nevertheless reveal full deuterium incorporation from the accelerator into the a-position of the fatty acid moieties of the randomized triglycerides in the interesterification reaction accelerated by acetone-d 6 . This experimental observation and its support by the conclusions from theoretical calculations prove unambiguously that the enolate mechanism is the major route in the low-temperature base-catalyzed interesterification processes.…”

“…As expected, no significant signals could be seen in the 2 H-NMR spectrum of the sample from the acetone-accelerated reaction (Fig. 11A), whereas a broad multiplet centered at 2.5 ppm was detected in the spectrum of the reaction product of the reaction accelerated by acetone-d 6 (Fig. 11B).…”

“…Addition of acetone-d 6 to the acetone-d 6 -accelerated sample yielded two distinct signals at 2.25 and 2.5 ppm (Fig. 11D), proving that the deuterium signals in the acetone-d 6 -accelerated sample did not stem from residual acetone-d 6 . Although the integrals in proton-decoupled 2 H-NMR spectra cannot be used for accurate quantification, it can be estimated from the above addition experiment that practically all deuterium atoms of the acetoned 6 used for accelerating the interesterification reaction had been incorporated into the a-positions of the fatty acid moieties of the resulting randomized triglyceride mixture.…”

“…As already pointed out by Coenen [5], the 'glycerolate' mechanism does not satisfactorily explain why the intramolecular interesterification is much faster than the intermolecular reaction [6].…”