Kinetic thermal analytical study of saturated mono-, di- and tri-glycerides
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Kinetic thermal analytical study of saturated mono-, di- and tri-glycerides M. Tomassetti • G. Favero • L. Campanella
Italian Special Issue Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract A thermal degradation study using TG–DTG thermogravimetry was performed on three saturated fatty acids esterified with glycerol (i.e. glyceryl-tristearate (C18), -tripalmitate (C16) and -trimyristate (C14)) at different heating rates. In addition, thermogravimetry (TG) and derivative thermogravimetry (DTG) of glyceryl di-stearate and glyceryl mono-stearate were also carried out at different heating rates. A deconvolution procedure applied to the first process and overlapping at least two steps between about 200 and 350 °C, enabled the activation energy of decomposition to be determined both by the Kissinger and the Ozawa–Flynn–Wall isoconversional methods for the deconvoluted steps of the above-mentioned fatty acids. Keywords Pure tri-glycerides Di- and mono-glycerides Kinetic analysis Thermal decomposition
Introduction In view of the important role of food oils in human diet, numerous studies have been carried out on these food products [1, 2], in particular on the oxidation process involving them. Also our research team in recent years has focused growing attention on the study and analysis of these important foodstuffs. For instance, work was done on the rapid analysis of the polyphenol content of extra-virgin M. Tomassetti L. Campanella Department of Chemistry, University of Rome ‘La Sapienza’, P.le A. Moro, 5, 00185 Rome, Italy G. Favero (&) Department of Chemistry and Drug Technologies, University of Rome ‘La Sapienza’, P.le A. Moro, 5, 00185 Rome, Italy e-mail: [email protected]
olive oil [3] and the determination of hydroperoxides generated by the rancidification process by constructing ad hoc Organic Phase Enzyme Electrodes (OPEEs) [4], or by developing a yeast cell biosensor capable of simultaneously evaluating the aspects of total toxicity produced by the rancidification processes [5]. Continuing our research on the kinetic aspects of the oil decomposition processes, thermoanalytic investigations [thermogravimetry (TG), derivative thermogravimetry (DTG)] were recently carried out of the oxidative thermal breakdown of several of the principal tri-glycerides, i.e. the most important constituents of food oils [6, 7]. The present report instead refers to heuristic studies of the thermal breakdown of two homogeneous series of saturated glycerides of the same type (see Table 1). The first series contained constantly saturated mono-, di- or tri-glycerides esterified with the same type of fatty acid, the second series contained saturated tri-glycerides esterified with fatty acids, which differed among themselves only in the length of their chain, that is (C18), (C16) and (C14). The experimental investigation was carried out using dynamic air thermogravimetric analysis (TG, DTG), endeavouring as far as possible to compare and critically evaluate the relatively small number of relevant thermal data report
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