Thermo-oxidative degradation of aromatic flavour compounds under simulated tobacco heating product condition

• Published in: Journal of analytical and applied pyrolysis 2018-09, Vol.134, p.405-414
• Main Authors: Blazsó, M., Babinszki, B., Czégény, Zs, Barta-Rajnai, E., Sebestyén, Z., Jakab, E., Nicol, J., Liu, C., McAdam, K.
• Format: Article
• Language: English
• Subjects: Aromatic flavours; Low temperature pyrolysis; Py-GC/MS; Thermo-oxidative decomposition; Tobacco heating products
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/j.jaap.2018.07.007

•Thermo-oxidative treatment of aromatic flavours can lead to objectionable products at 300 °C.•Thermo-oxidation-GC/MS is a useful screening method to identify the products.•Characteristic reaction schemes were assumed to explain the formation of the products.•The common oxidation reaction proved to be dehydrogenation of alkyl substituents.•Phenylacetic acid and phenylethyl esters may degrade to styrene by thermo-oxidation. A modified pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) method was used to evaluate the thermo-oxidative degradation of 34 flavour compounds containing aromatic sub-units, in 9% oxygen / 91% nitrogen at 300 °C with 5 min isothermal holding. This set of pyrolysis parameter was used to simulate heated tobacco products. The main types of reactions of these aromatic species under these conditions were relatively mild oxidation and thermal division resulting in the formation of benzaldehyde and other aldehydes, ketones, and styrene. The highest yield of these products was estimated to be around 10%, occurring where the molecular structure and reactivity of the compound was susceptible to oxidation or bond scission. Representative reaction schemes were proposed to explain the formation of the detected products. The results proved that styryl moiety present in some aromatic flavour compound did not decompose to styrene under the conditions applied, rather, styrene was generated from phenylacetic acid and phenylethyl esters by thermal cleavage at 300 °C.