Premox?

We did a dinner last night that combined the just opened season spot prawns with various Chablis. Among other things (like how it takes a real man/woman to chow down on deep fried prawn heads), the conversation included the issue of premox. Here is a youtube episode of Pierre-Antoine Rovani of Remoissenet discussing this phenomenon. I've often wondered why premature oxidation seemed to suddenly become and issue in the mid 1990s but not before.

http://www.youtube.com/watch?feature=player_embedded&v=Nnl3d_K3lx0#

"You don't have any lees because you didn't press, and all your anti-oxidants were in the skins and pulp. So you didn't get them out. The little that you did get out you threw out, cause you did a decantation off gross lees…so you left that stuff in the tank. And then you put clear juice with no anti-oxidants in a barrel…"

Rovani is pretty funny. He could be the world's first oenophile stand-up comedian.

Well, I can't agree with everything he said, but will agree with part. Overproduction in the vineyard leads to higher pH. High pH coupled with low free SO2 coupled with presence of metal ions certainly predisposes a wine to premature oxidation. In this anti-SO2 age, people naturally add less SO2 than 10-20 years ago. But he's correct when he claims less phenolic antioxidant capacity in wine. But there's a reason for that-- most people don't want to age a wine, but rather desire consumption immediately upon purchase. Phenolics= bitterness and/or astringency, which means aging is often required. Consumers on this board are aberrations compared to the norm, in that here it is not unusual to cellar wine extensively.

[David M. Bueker]

Let's be careful. There has yet to be any conclusive proof about the underlying cause(s) of premox. Rovani talks a big game, but he doesn't really know.

Something happened in the mid to late '90s. Unfortunatley there were a host of changes being made to winemaking, bottlings processes, vineyard management, etc at the time, so isolating the specific vaiables that get to premox is not an easy task.

David, we can't say definitively what caused premox in this or these cases, but we can set up situations in the laboratory where control wines oxidize prematurely. Whether there are more determinants of it than we have identified, we have the capability to define at least some of the potential factors. I certainly agree about Rovani, but as I say, he did touch on a factor or 2, and at the same time, was incorrect with others. Overcropping seems to raise pH, and we know pH to be one of the potential factors in premature oxidation. Whether or not increased use of free-run is a factor is speculation on his part, because typically, overage is just declassified rather than destroyed, so there is no benefit to just using free-run juice. Those growers who are most interested in limiting crop will prune and thin to that effect, and will crush and press in the normal manner. One would think that the top wines would be produced with this eye towards quality through limited vineyard production, and yet top wines are affected as well.

[David M. Bueker]

Craig,

Science experiments are great, and can potentially lead to a solution, but so far nobody has done anything to demonstrably make the situation better.

I remember when Rovani raised the premox issue on the eRP forum back in 2005. Whether or not corks were the issue, he certainly came across as scientifically/oenologically ignorant (or at best, logically inconsistent), and presented arguments that were not convincing (thus the reaction on that forum's thread back in 2005, which he refers to in the video).

It's true that phenolics from unclarified must provide antioxidants, but so do yeast lees. Rovani says in the video that, having used clarified must, "what antioxidants would you have? None". That is just incorrect. A must/wine with additional phenolics (sourced, for example, from skins) would have greater concentrations of antioxidants, but fermentation is an inherently "reductive" process, and the yeast lees from fermentation would certainly provide a degree of antioxidant

He says that corks can't be the issue "because everybody in the world uses the same corks". Then he goes on to suggest that the issue is a lack of oxidative protection (brought about by must clarification). But many wineries in the world use that same technique, so by the same logic must clarification can't be the issue either!

He doesn't have the answer (though he has always seemed to make out that he does), and no-one else currently seems to either.