Perhaps we have not explained the science clearly enough for the benefit of
the non chemists in the group.  Application of butyric anhydride to a fume
board would not mean that it would leave residues of the anhydride in the
honey.  This would be due to two reasons, one physical, one chemical.

The physical reason is that due to its low vapor pressure, little anhydride
would ever evaporate from the fume board (and thus never reach the honey).
Chemically, it would react with the water vapor hitting the fume board, and
transform into butyric acid, which would then readily evaporate.  The small
amount of anhydride that might actually evaporate would tend to react in
the air with water vapor prior to ever reaching the combs.

And then any tiny amount of anhydride that might ever reach the combs would
immediately react with the water in the honey and be transformed into
butryic acid, as explained by Kwan in the study cited by Pete: "When either
of the pure anhydrides, butyric or propionic, were added to honey in
amounts up to 20 ppm, no anhydride could be seen in the subsequent ether
extract analysed by gas chromatography.  Thus while both of the anhydrides
could be volatile enough in omparison with their acids, to reach the honey,
they would be rapidly hydrolysed by water in the honey to leave their
corresponding acids as residues."

Thus, this would make any requirement for a maximum residue limit moot.  It
would be difficult to make the case that any anhydride were actually
applied to the honey in the first place, since even if a few molecules
actually reached the honey, they would be immediately degraded into a
different chemical--butyric acid.

Andy then during transport, storage, and extraction of the honey combs,
those butryic acid residues would tend to evaporate off into the air.  Kwan
confirmed that butyric acid is a natural component of honey, and is
"naturally found in foods such as butter and cheese at much higher levels
than any that we detected in honey samples."

From the standpoint of someone who is concerned about chemical residues in
their food, I simply cannot get too excited about residues from using
butyric anhydride on a fume board.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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