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.
Stable isotope ratios (SIRs) of C, N, H and O have been exensively used in fruit juices quality control (ENV and AOAC methods) to detect added sugar and the watering down of concentrated juice, practices prohibited by European legislation (EU Directive 2012/12). The European Fruit Juice Association (AIJN) set some reference guidelines in order to allow the judging of the genuiness of a juice. Moreover, various studies have been carried out to determine the natural variability of SIRs in fruit juices, but none of these has investigated SIRs extensively in authentic citrus juices from Italy. In this work, about 500 citrus juice samples were officially collected in Italy by the Italian Ministry of Agricultural and Forestry Policies from 1998 onwards. (D/H)(I) and (D/H)(II) in ethanol and δ(13) C(ethanol), δ(13) C(pulp), δ(13) C(sugars), δ(18) O(vegetalwater), δ(15) N(pulp), and δ(18) O(pulp) were determined using Site-Specific Natural Isotope Fractionation-Nuclear Magnetic Resonance and Isotope Ratio Mass Spectrometry, respectively. The characteristic ranges of variability in SIRs in genuine Italian citrus juice samples are here presented as well as their relationships and compliance with the limits indicated by the AIJN and others proposed in the literature. In particular, the Italian range of values was found to be not completely in agreement with AIJN guidelines, with the risk that genuine juices could be judged as not genuine. Variety seems not to influence SIRs, whereas harvest year and region of origin have some influence on the different ratios, although their data distribution shows overlapping when principal component analysis is applied.
This paper presents the results of a collaborative study involving seven laboratories and concerning two samples of wine vinegar, one of apple vinegar and four of balsamic vinegar. The aim of the study was to define standard deviations of repeatability (sr) and reproducibility (sR) for vinegar and balsamic vinegar stable isotope ratios of H (D/H), C (δ13C) and O (δ18O), in order to establish them as fully recognized official standards. Acetic acid was extracted and subjected to (D/H)CH3 and δ13C analysis. δ18O analysis was performed on whole samples. The grape must solution remained after distillation of balsamic vinegar was fermented and the resulting ethanol was subjected to (D/H)I, (D/H)II, R and δ13C analysis. The sr and sR were 0.6 ppm and 1.1 ppm for (D/H)CH3, 0.14‰ and 0.25‰ for δ13C of acetic acid, 0.1‰ and 0.17‰ for δ18O of water, 0.19 ppm and 0.64 ppm for ethanol (D/H)I, 1.14 and 1.31 ppm for (D/H)II, 0.09 and 0.11‰ for δ13C of ethanol. These data are in line with those in the literature or reported in corresponding official methods, and sr and sR of balsamic vinegar are in line with those of vinegar and must.
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