Yes I know. But is there any reason to think that the difference in reaction rates, as measured in ratio terms, will generally tend to be smaller at lower temperatures than at higher. This is the point I was inquiring about.
I referenced a thread from last year that discussed this topic, and had a link to a nice article which outlines the logic of “bad” aging at higher temperature. Turns out the link to the article has changed since then, so here is the updated link
http://www.wineperspective.com/how-temperature-affects-wine-aging/
I’ll try and restate what’s in that article:
If reactions occurred at accelerated rates as temperature increases, always in the same ratio, then there really wouldn’t be any harm in storing wine at any temperature, it would just follow the same aging path at a faster rate. If this were the case, there would be no such thing as a cooked bottle, just one that has seen higher temps and progressed further.
As has been said before, among the various reactions in a bottle that go on during aging, the activation energies of those reactions surely cover a range of values. But if that simple assumption is too much to make, think of it this way: We know that a wine stored at higher temperature ages differently than one stored at lower temperature, and I think it’s safe to say most people would generally agree that the bottle stored at high temp isn’t going to develop as well as the one stored at low temp. That means there are “bad” chemical processes happening at the higher temp out of proportion to what’s happening at low temp. (Let’s also note that in addition to reactions speeding up, it’s also likely that as that happens other intermediate products are being produced in sufficient quantity to allow secondary reactions to occur which produce products that aren’t generated in detectable quantity at lower temperature, but I’m just going to stick with the simple comparison of the first level reactions for now).
Now we’re at the heart of the linked article’s numbers: drawing on the above, let’s look at a simplified case where there is a “good” reaction and a “bad” reaction. The good reaction dominates at lower temperature (because the wine ages well), while the bad reaction becomes more evident at high temperature (because we’ve agreed that the bad products occur at high temp). By definition, the good reaction must have a lower activation energy (Ea), because its rate is (relative to the bad reaction) higher at low temperature; and the bad reaction must have a higher activation energy, because its rate is lower (think of activation energy as the height of the bar for a high jumper - the higher it is, the more energy the jumper needs, and the harder it is to clear the bar). This is all consistent with basic reaction kinetics, as described by the Arrhenius equation, which says that reactions with higher Ea will be sped up more by increased temperature than reactions at lower Ea.
Maybe an example will help: Say the good reaction has an Ea of 50kJ/mol. If we increase the storage temperature from 55 to 75 (F), that would result in the good reaction rate increasing by a factor of 3.96. Let’s give the bad reaction an Ea of twice as much, or 100kJ/mol. For the same change in temperature from 55 to 75, that reaction rate would increase by a factor of 15.7. So the “bad” reaction would be happening about 4 times faster than the “good” reaction at 75 as it does at 55.
That’s the simple, handwaving explanation of why a wine ages differently, and generally more poorly at elevated temperature.
Alan - And that’s just the chemical aspects. As we’ve discussed in prior threads on this theme, there are biological things going on in wine. As I recall, brett multiplies much faster above a certain temperature. So an increase of a few degrees that might be benign from a purely chemical standpoint might have a bigger effect on something like brett.
Well, I’m just a lowly physical chemist, I know nothing of this biology you speak of. But yeah, you’re exactly right ![[cheers.gif]](/uploads/db3686/original/2X/0/0ff9bfcdb0964982cd3240b6159868fbdf215b1a.gif "cheers"){kind=small}
Tagging this thread with my favorite marker for ease of future reference: ecclesiastical.
That may well be what most people would say but on the basis of what evidence (for, say, a temperature range from 10 to 20 C)? Obviously, the bottles (there’d better be a sample, not a single one) stored at higher temperature should be aged for a shorter time than the bottles stored at lower temperature for the comparison to be meaningful. This in turn means that the tastings to be compared cannot take place at the same time.
Alan
A plausible explanation for differential ageing characteristics. As John pointed out low level brett just explodes when stored at higher temp. But its the lack of freshness and vitality with age that I find lacking in wines stored at higher temperatures for longer periods.
As a side, I was taking to a wine shopperson last year during an inshop scotch whisky tasting. He was extolling the virtues of a couple of Australian whiskeys stating that the higher temperatures age them much faster. He said “What takes Scotch 18 years to achieve, we can locally get those characteristics in just a few years”. Comparing all whiskeys side by side, apart from obvious quality differences, it was the lack of vitality and subtle nuances that were missing with accelerated ageing at high temperatures.