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From:
James Fischer <[log in to unmask]>
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Date:
Thu, 15 May 2003 13:40:50 -0400
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Peter Bray knows his biochem, and pointed out
something that I neglected to explain clearly:

> In fact water is not just water.  Today isotope ratio analysis is
> starting to have immense impacts in all facets of  food industries.
> Here in New Zealand it has been successfully used to determine that
> water was added unlawfully to wine.

Many people have heard about "isotope ratio tests" being done on
honey before, but what Peter mentioned is NOT the (perhaps)
better-known "carbon isotope ratio" test, which is good for finding
HFCS or other sugars that have been added to honey.

I'll try to explain both tests in plain English, since I can see a
need to create a formal definition for honey that is based upon the
tests that all agree can be used to detect adulteration.  (Yes, this
implies that the "definition" becomes subject to change with each
new generation  of test equipment, but it would be better than what
we have now, which is no formal definition at all.)

The CARBON isotope ratio test:

  exploits the fact that honey comes from plant nectar.  Plants use
  photosynthesis, and the overwhelming majority of nectar-producing
  plants use "C3" type photosynthesis.  As luck would have it, both
  sugar and corn plants use only "C4" photosynthesis.

  I'm not going to bore everyone with a long-winded description of the
  differences between "C3" and "C4", as the whole process of photosynthesis
  and the "Calvin cycle" is very complex.  Just accept that the two
  processes that metabolize sun, CO2 and water are very different, and
  produce very different mixes of carbon isotopes.

  Because the two processes are different, one can look at values that
  (for nectar-based sugars, like honey) range from "20 to 30", but for
  non-nectar-based sugars, range from "10 to 16".  Since there is no
  overlap in the results of testing the output of "C3" and "C4" plants,
  a mix of the two (honey and HFCS, for example) can be detected with
  very high accuracy, since "mixing" does not create a true "even mix".

  Now, some producers, notably China, have taken issue with tests like
  the carbon isotope test, claiming that the plants that produce nectar
  in their ecosystems are somehow "different" from the rest of the planet,
  and therefore produce different profiles and ratios.
  (Yeah, right.  Howcome they never send us any plants to test?)

But look out con artists - here comes the WATER isotope ratio test,
which is impossible to argue or handwave away:

  It is even more subtle, and has not been around very long. It depends
  upon the fact that evaporation of water in plants takes place through
  "transpiration" via leaves and fruit.

  The water component of fruit juices and nectar is higher in Hydrogen
  and Oxygen-18 than the water drawn in by the roots. ("O-18 is an isotope
  of oxygen, the 3 major isotopes of dissolved oxygen are "O-16", "O-17",
  and "O-18").  Plants really do make "special" water.  It would be
  really tough and expensive to try and counterfeit this isotope ratio
  for adulteration purposes.

  There is very little difference between one plant and another in the
  method of transpiration of water, so the water isotope test is not
  subject to much variation due to plant species, and is therefore not
  subject to argument about "my plants" versus "your plants".

  So, if someone claims that orange juice "from concentrate" is really
  "fresh-squeezed", you can test the isotopes of the water, and easily
  prove that the water in the juice came from a water-treatment plant
  rather than from a leaf-bearing plant.  Even if they use distilled
  water, it would stick out like a sore thumb.

  So, if someone uses the "ultra-filtration" method, we can clearly
  detect that the honey contains water from non-plant sources.  Since
  there is no scenario where anyone would deliberately add water to
  honey in any legitimate honey-processing, any "non-plant" water
  would be a dead give-away.  The water isotope test cannot be argued
  away, since water all over the planet has well-known isotopes,
  defined by the various "meteoric water lines", none of which are even
  close to the ratios you get from any plant source.

  And if someone tries to play the "water in wine" trick, you can nail
  them, too.  (We have no samples to test the "water INTO wine" trick,
  but no one has demonstrated the process for several thousand years.)


                jim (who, after all that, needs a drink)

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