Thujone in Pre-Ban Absinthe
Got an email last night about a new paper which has been released looking at the levels of Thujone in vintage Absinthes. It conclusively disproves the assertion that pre-ban Absinthe was thujone-enriched.

The new paper co-authored on the chemical composition of vintage absinthe (http://www.thujone.info/thujone-absinthe-39.html ) has attracted lots of comment, mostly gratifyingly favourable. It's already listed on PubMed and most of the other key research databases. There are two questions though which I've been asked repeatedly, which I thought I should address briefly here:

"I see results for many different absinthes, but not for bottles from the Pernod-1914 cache. Why weren't these bottles included?"

Over and above the 13 pre-ban bottles listed in the paper, we also tested about half a dozen other pre-ban bottles, including several from the Pernod-1914 cache. They were not included in the final results simply because they lacked original labels, and we did not want to let the article get bogged down with all the detailed background information necessary to prove the authenticity of these bottles. It was cleaner and simpler to confine the published results to perfect bottles with intact labels. Had we included the unlabeled bottles though, it would have made no difference to the results ? their analyses were within the same statistical ranges as the labeled bottles. In other words, including them would not have changed our conclusions at all. We may at some stage in the future informally release these additional results.

"OK, I understand your tests show only low levels of thujone in the vintage bottles, but isn't it possible that the thujone was initially there, and has simply degraded over the last century into something else?"

The short answer is no, almost certainly not. The answer's a little technical, but here it is in the (relatively) simple terms:

"Stability of Pulegone and Thujone in Ethanolic Solution", Frölich and Shibamoto (1990)
http://www.thujone.info/thujone-absinthe-40.html

This passage is important:
"No change in the thujone concentrations was noticed during the storage experiments in 100% ethanol and 30% ethanol at either pH 2.5 or pH 6.5. At pH 11.5 a very rapid epimerization of alpha-thujone to the 5 times less toxic beta-thujone (Rice and Wilson, 1976) took place as reported by Hach et al. (1971) and reached an equilibrium of about 1:2 alpha-thujone to beta-thujone after about 20 h. A comparison of the reaction rates at 20"C in sunlight and in the dark showed that the reaction was independent of the influence of light. At the different temperatures (100, 20, and 0 "C), nearly no difference in reaction rate was observed."

What we find in this experiment is the degradation of thujone can be effected via a sufficient pressure of photoirradiation with 310nm UV light (but this is a level way above anything naturally occurring). Under that pressure, thujone undergoes decorbonylation to 5-methylene-6-methyl-hept-2-ene. We of course also made full scan analyses of the pre-ban products. 5-methylene-6-methylhept-2-en was NOT contained in any of the samples.

So not only is there no evidence of any thujone degradation products, but NO degradation at all was observed in real world conditions - ie in the absence of sufficient photoirradiation pressure, despite exposure to sunlight, wide differences in pH, and temperature ranges from 0-100?C.

A further indicator that thujone doesn't deteriorate significantly over time, is the fact that modern absinthes made scrupulously according to Belle Epoque recipes (for instance, both the Doubs Mystique and Roquette 1797 that I distill in Pontarlier) generally have thujone levels in the same range as the pre-ban absinthes we tested - roughly around 20-35mg/l.

As I've previously said, it's my contention that the effects of Absinthe are as a result of synergistic processes, and not due to Thujone Intoxication. It's Good for you. It has Herbs in it. ^___^