Toward the stereochemical identification of prohibited characterizing flavors in tobacco products: the case of strawberry flavor

With the revision of the European Tobacco Products Directive (2014/40/EU), characterizing flavors such as strawberry, candy, vanillin or chocolate will be prohibited in cigarettes and fine-cut tobacco. Product surveillance will therefore require analytical means to define and subsequently detect selected characterizing flavors that are formed by supplemented flavors within the complex matrix tobacco. We have analyzed strawberry-flavored tobacco products as an example for characterizing fruit-like aroma. Using this approach, we looked into aroma components to find indicative patterns or features that can be used to satisfy obligatory product information as requested by the European Directive. Accordingly, a headspace solid-phase microextraction (HS-SPME) technique was developed and coupled to subsequent gas chromatography-mass spectrometry (GC/MS) to characterize different strawberry-flavored tobacco products (cigarettes, fine-cut tobacco, liquids for electronic cigarettes, snus, shisha tobacco) for their volatile additives. The results were compared with non-flavored, blend characteristic flavored and other fruity-flavored cigarettes, as well as fresh and dried strawberries. Besides different esters and aldehydes, the terpenes linalool, alpha-terpineol, nerolidol and limonene as well as the lactones gamma-decalactone, gamma-dodecalactone and gamma-undecalactone could be verified as compounds sufficient to convey some sort of strawberry flavor to tobacco. Selected flavors, i.e., limonene, linalool, alpha-terpineol, citronellol, carvone and gamma-decalactone, were analyzed further with respect to their stereoisomeric composition by using enantioselective HS-SPME-GC/MS. These experiments confirmed that individual enantiomers that differ in taste or physiological properties can be distinguished within the tobacco matrix. By comparing the enantiomeric composition of these compounds in the tobacco with that of fresh and dried strawberries, it can be concluded that non-natural strawberry aroma is usually used to produce strawberry-flavored tobacco products. Such authenticity control can become of interest particularly when manufacturers claim that natural sources were used for flavoring of products. Although the definition of characterizing flavors by analytical means remains challenging, specific compounds or features are required to be defined for routine screening of reported information. Clarifications by sensory testing might still be necessary, but could be limited to a few preselected samples.