Carbon Isotopic Ratios and enantiomeric distribution of selected volatiles as parameters for quality assessment of citrus liqueurs determined by HS-SPME coupled to GC-C-IRMS and ES-GC

Liqueurs derived from Citrus fruits, generally obtained from maceration of the peel or the whole fruits of lemon, mandarin and bergamot in ethanol, water and sugar, are a category of spirit drinks in which the addition of nature-identical flavouring substances and preparations is forbidden. The traditional production methods and the protection of geographical indications of spirit drinks are governed by the Regulation (EC) No 110/2008 of the European Parliament and of the Council. Authenticity assessment of home-made and commercial Citrus liqueurs was performed using Headspace-Solid Phase Microextraction (HS-SPME) coupled to Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS). Additional analyses were performed on all the samples, by means of enantioselective Gas Chromatography (Es-GC), measuring the enantiomeric distribution of the chiral volatile components, extracted by the same HS-SPME technique. Moreover, Gas Chromatography–Mass Spectrometry (GC-MS) analyses were also conducted by using HS-SPME, in order to obtain information on the qualitative aspects of the samples. Additional analyses also revealed the lack of the monoterpene fraction in some commercial samples. The results obtained by GC-C-IRMS on the liqueurs were compared with the carbon isotopic ratio ranges determined on authentic cold-pressed lemon, mandarin and bergamot essential olis. In particular, it emerged that the carbon isotope ratio of the volatile compounds of all the home-made drinks fell into the correspondent authenticity range of the cold-pressed essential oil, while some commercial products did not match the correspondent ranges of authenticity. GC-C-IRMS, ES-GC and GC-MS coupled with HS-SPME have shown to be a complete and rapid tool for the quality control investigation of Citrus liqueurs. The results obtained by these techniques were in good agreement, revealing the non-natural Citrus aromas in some commercial liqueurs, as well as assessing the genuineness of the home-made ones.