Abstract. The implementation of stable isotope applications in official food analyses began in 1990. At that time the first method to detect sucrose from sugar beet or sugar cane in wine by Deuterium-Nuclear Magnetic Resonance ( 2 H-NMR) of ethanol, also known as SNIF-NMR ® -Method became adopted officially by the European Commission. This was a milestone for an improved authentication of wines and other food stuffs. In connection with methods using Isotope Ratio Mass Spectrometry (IRMS), stable isotope ratio analysis is one of the most powerful analytical tools for authentication of wine. The fundamentals of biotic and abiotic stable isotope fractionation and the analytical methods which are used in authentication of wine are summarized. Principles of authentication of some wine constituents like sugar, ethanol, organic acids, glycerol, and carbon dioxide as well as proof of geographic origin are reviewed. By selected example of anonymized cases, proof of adulterations (e.g. chaptalization, addition of water or mislabeling) using monovariate, bivariate, and multivariate data evaluations are discussed. It is shown that for this purpose databanks are generally indispensable. In their absence cut-off values, derived from long-term observations help to detect clear adulterations.

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A collaborative study of the site-specific natural isotope fractionation-nuclear magnetic resonance (SNIF-NMR) method for detecting added beet sugar in fruit juices is reported. This method is complementary to the stable carbon isotope ratio analysis (SCIRA) (AOAC Official Methods 981.09 and 982.21), which can detect sugars derived from plants exhibiting C4 metabolism (corn and sugarcane). It is based on the fact that the deuterium content at specific positions of the sugar molecules is higher in fruit sugars than in beet sugar. The fruit juices are fermented, and the alcohol is distilled with a quantitative yield and analyzed with a highfield NMR spectrometer fitted with a deuterium probe and fluorine lock. The proportion of ethanol molecules monodeuterated on the methyl site is recorded. This parameter (D/H)i is lowered when beet sugar is added to a fruit juice or concentrate. The precision of that method for measuring (D/H)i was observed to be similar to that of other isotope ratio methods: sr values ranged from 0.19 to 0.25 ppm and SR values varied between 0.21 and 0.37 ppm. An excellent correlation was observed between the percentage of added beet sugar and the (D/H)i isotope ratio measured in this collaborative study. Consequently, all samples in which beet sugar was added were found to have a (D/H)i isotope ratio significantly below the normal value for authentic juice or concentrate of that fruit. The SNIF-NMR method for detection of added beet sugar in fruit juices has been adopted by AOAC INTERNATIONAL.

In this paper, we investigate whether the analysis of stable isotope ratios D/H and ¹³C/¹²C in ethanol and acetic acid and of ¹⁸O/¹⁶O in water can be applied to the ingredients of "aceto balsamico di Modena IGP" (ABM) to evaluate their authenticity. We found that impurities in the extraction solution do not affect the ¹³C/¹²C of acetic acid and the D/H values of acetic acid are not affected under a composite NMR experiment. The standard deviation of repeatability and standard deviation of reproducibility are comparable in wine vinegar and ABM and generally lower than those quoted in the official methods. This means that the validation parameters quoted in the official methods can also be applied to the ingredients of ABM. In addition, we found no changes in the isotopic values from wine to vinegar and to ABM, and from the original must to the ABM must, providing experimental evidence that reference data from wine databanks can also be used to evaluate the authenticity of vinegar and ABM.

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The average carbon isotope value (delta(13)C) of 63 samples of glycerol from over 30 different sources has been determined. The results indicate that it is possible to distinguish the glycerol obtained from the glycerides produced in plants following C-3 and C-4 carbon fixation pathways. The samples obtained from animal sources seem to reflect the composition of the material consumed, as well as that produced by sugar fermentation.

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