Page 182 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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There are, however, complicating factors. For example, the d C values of
honey range from –22.5 to –27.4‰ (standard deviation = 0.98), while those
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derived from CAM plants with d C values range from –12 to –18‰ and
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require special limits in determining the authenticity. The Association of
Official Analytical Chemists has established isotopic analysis procedures for
providing legal proof of adulteration of honey and apple juice. Considering
possible variations of the natural isotopic composition of a particular product,
a conservative approach is adopted for the interpretation of analytical results;
usually a limit of four standard deviations (1 in 25,000 error probability) of
the natural variability of the product is set for concluding that the product
is adulterated. Thus, –21.5‰ was used as the limit which could allow as much
as 20% of added C4 sugars. An internal standard carbon isotope ratio analysis
(ISCIRA) approach was used to improve the sensitivity and objectivity in
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testing honey with d C values less negative than –23.5‰ (2 standard devi-
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ation less negative than the mean). This method compared the d C values
of the protein isolated from the honey and that of the honey itself. A difference
greater than –1‰ indicated the presence of significant amount of added C4
sugars. This index (1‰) is equivalent to 7% of added material. 59
Using a similar approach, it is possible to prove whether a food sample
is of synthetic or of biogenic origin. Examples of these studies include the
differentiation of:

1. Vanillin extracted from vanilla beans of different geographic origins,
and that synthesized from lignin, eugenol (clove oil), or guaiacol (a
coal tar) 60
2. Vinegars obtained by biogenic fermentation and by synthetic
process 61
3. Beers brewed with barley alone, and those with the addition of maize
or petrochemical carbon dioxide derived from natural gas 62

To detect fraudulent adulteration of high premium olive oils, Angerosa
et al. compared d C values of the aliphatic alcoholic oil fractions and found
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those of the adulterant pomace oil to be significantly more negative than
those of virgin and refined olive oils. In a subsequent study, Angerosa et al.
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employed both C and O isotope analysis to determine geographical origin
of olive oils according to climatic regions in different Mediterranean coun-
tries such as Greece, Morocco, and Spain. 64

4.4.2 Dietary Composition as a Basis for Sample Differentiation
A more specific study has been reported for coffee and tea. Carbon, hydrogen
and oxygen isotope compositions of chemically pure caffeine derived from

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