Charts of the day, wine-heat edition

By Felix Salmon
February 8, 2012
blogged a paper about the way in which wineries lie about the alcohol content of their wines. Now, the same authors have a new paper out, trying to get to the bottom of exactly why wine is getting hotter.

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Last year, I blogged a paper about the way in which wineries lie about the alcohol content of their wines. Now, the same authors have a new paper out, trying to get to the bottom of exactly why wine is getting hotter.

One thing I like about this paper is that it doesn’t look directly at wine-alcohol levels, but moves back a step to the sugar content of the grapes going into the wine. If you turn high-sugar grapes into wine, one of two things has to happen: either you get sweet wine, or you get high-alcohol wine. Since taste in wine is getting dryer rather than sweeter over time, higher-sugar grapes mean hotter wine. And those grapes are definitely getting sweeter, especially when it comes to white wine. Here are the charts for California:

brix.tiff

Is there a global-warming thing going on here? After all, warmer temperatures mean sweeter fruit. But, no. Here are the temperatures of California’s wine-growing regions for the years since 1990 that sweetness has been rising quite dramatically:

gr.tiff

But we kinda knew this already. The most interesting thing in the paper, is not that hotter wine is unrelated to global warming. Instead, it’s that hotter wine is quite strongly related to price:

Sugar content of grapes at harvest was relatively high for red varieties and premium varieties, and for grapes from ultra-premium and premium regions. The same categories tended to show evidence of faster growth rates in sugar content as well… In all of the models, the analysis shows a higher propensity for growth in sugar content for premium varieties, compared with non-premium varieties… This feature and the patterns of the level of sugar content among regions and varieties could be consistent with a “Parker effect” where higher sugar content is an unintended consequence of wineries responding to market demand and seeking riper flavored, more-intense wines through longer hang times…

We found that the region with the lowest price of wine grapes (under $500 per ton) had significantly lower average degrees Brix at crush compared with all other regions… It may be profitable, in producing lower-priced wines, to opt for a higher yield of wine per ton of grapes in exchange for lower Brix.

Simplifying, you can think of vineyards in one of two ways. Either they’re a source of grapes which get sold by the ton, in which case you want to maximize the yield. That, in turn, means lower sugar content. Alternatively, they can be a source of carefully-cultivated grapes which get turned into premium wine selling for $20 per bottle and up. In that case, the quality of the grapes starts trumping their quantity. And it’s pretty clear that what winemakers want, if they’re going to sell expensive wine, is grapes with a lot of sugar. That’s their expressed preference, anyway.

All of this is consistent with what I wrote last year — that wine drinkers say that they want lower-alcohol wines, and will even go so far as to prefer to buy wines with lower alcohol numbers on the label. But when they actually taste the stuff, in general the higher the alcohol the happier they are. Especially when the wine is expensive.

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