CARBON ISOTOPE RATIO MS (GC-C-IRMS) AND MULTIDIMENSIONAL GC (MDGC) FOR THE AUTHENTICITY ASSESSMENT OF NATURAL FOOD FLAVORS

Enantiomeric ratios of chiral volatile components represent useful parameters widely applied to assess of the authenticity of natural products based on the characteristic chiral selectivity of the biosynthetic pathways of secondary metabolites. However, the enantiomeric ratios of volatile components in a selected natural matrix can vary depending on natural phenomena (cultivar of the plant, seasonal variation, etc.) or can be modified by the procedure used for extraction or by chemical reactions which can occur during the shelf life of the final product. Thus, the assessment of authenticity in food products often must be supported by multiple analytical techniques (physico-chemical analyses, GC, es-GC, HPLC, etc.). Differently, the carbon isotope ratio of pure compounds is strictly dependent on the plant biochemistry and on geographical origin of the originating plant. It is not subject to seasonal variation nor to the extraction procedure used. In this contribution will be presented the results obtained from an extensive study carried out by the combination of enantioselective chromatography and the isotope ratio determination of volatiles in numerous samples of essential oils of different Citrus species; on extracts obtained from different anatomic parts of the Citrus plant (peel, leaves flowers and juice); on several samples of commercial and home-made Citrus liqueurs and on natural fruit flavours extracted by HS-SPME from the fresh fruits (strawberry, pineapple and peach) and the related artificially flavoured foodstuff. The analyses were carried out by Es-MDGC or by Es-GC and by GC-CIRMS, to determine if the combination of enantiomeric ratios with the carbon isotope ratios can be effective to assess the genuineness of the samples studied. The instruments used for this study are all commercially available. The advantage of this approach is the low number of variables which must be evaluated to assess the authenticity of natural products.