Winemakers fight global warming with science and tradition

Outdoor concrete tanks at a large winery in the Alentejo region of Portugal. Most of the tank is underground, which helps maintain temperature even as summers get hotter with increased global warming. The tanks are constructed by first digging the half-sphere pit, then filling a large balloon-like structure with air, and finally covering the balloon with concrete. The balloon is removed and the inside gets lined with concrete as well.

Note — this blog post was a finalist for the Millesima Blog Awards in the Wine and Technology Category, along with four others (you can see the badge I received on the right-hand margin of the blog).  Although I didn’t win the category, there was another chance to win a readers’ choice award, determined by reader voting.  This post came in third among the remaining posts — something I’m extremely grateful for considering that the people who came in first and second are extremely popular bloggers.  So thanks to you all for reading!

In my last post I mentioned some of the impacts of global warming on grape growers and winemakers, as told to me by winemakers at two European wine shows.  While extreme weather and shortened growing seasons were shared concerns, the winemakers also discussed geographic-specific issues, like changes to local wild yeast. 

So how are winemakers and grape growers coping?  As I mentioned before, it’s a mixture of both cutting-edge research and a return to older traditions.  And so far, farmers and winemakers are running ahead of their regional appellation authorities in adaptation to climate change.

There’s a bunch of active research on breeding from grape stock that seems to do better in the increasingly warmer weather.  In the long run, that will benefit everyone.   One area of breeding research focuses on growing smaller berries no matter the varietal.  In general, smaller grapes do better because the skin to juice ratio is higher and since lots of flavor comes from the skin, there’s more opportunity for flavor development during fermentation.

Another solution for some producers has come from something that seems counter-intuitive:  increasing the yield per vine (and hence, per hectare).  In general, grape growers strive for a particular yield range that ensures high-quality grapes.  Fewer grapes means less competition per grape for nutrients and the products of photosynthesis.  However, this also means that the sugar content increases more quickly than it would if the grape yield were higher.  More competition for resources per grape actually lengthens the growing season, because the grapes take longer to reach their optimal sugar content.  Longer ripening in turn means a longer time for flavor development – avoiding the problem of under-ripe flavors.

In general, increasing the yield has proved more effective for white wines than red wines.  Red grapes don’t seem to respond in quite the same way.  This may be different for some varietals, but the Portuguese winemaker I discussed the yield/quality issue with told me that greater yields don’t have the same effect for his red grapes.

Instead, he has turned to what he can do in the winery.  One of the keys is to minimize the “green” or under-ripe flavors during the winemaking process.  The more the wine or juice gets pumped around by mechanical means, the more likely it is the final product will have green flavors at the expense of riper ones.  I’ve written before about how pumps are the bane of many winemakers’ existences.  They still have to be used, of course, but minimizing their use – particularly during fermentation and initial aging — is key. 

Specifically, the winemaker told me he has stopped what’s called “pump-over.”  When pressed grapes and juice go in the tank, the skins usually float to the top.  In order to keep everything mixed and maximize skin contact, juice typically gets pumped from the bottom of the tank and sprayed over the skin mat at the top to mix. 

There are other ways of mixing the skins and juice, depending on the size of the tank or barrel.  If the fermentation vessels aren’t too large, winemakers can mix by hand.  It’s similar to batonnage, stirring up the wine in barrels to even out contact with the wood and the small particles suspended in the wine.  One of my French producers claims this is how she maintains upper body strength and tone.  Another of my producers told me that rolling up his sleeves and pushing the skins down into the juice in the barrel – and allowing visitors to do the same – gives those visitors a perfect selfie moment, in addition to being good winemaking practice.

But hand mixing in large tanks is impossible.  And the amount of mechanical mixing necessary to get everything in contact can create as much disturbance to the juice as pumping.  So this particular winemaker told me he has resurrected a 19th-century technique – using the carbon dioxide generated during fermentation to push the juice up over the skin mat.  A cone-shaped insert in the tanks guides the juice up the sides and down through a hole in the middle, gently mixing the skins and juice.  Normally, carbon dioxide vents out the top of the tank anyway, so it’s intriguing to know that it can have a beneficial use as well.

I also learned about a number of innovative storage techniques developed for use in larger wineries, including some dome-shaped vessels that are half underground and can be used in even the hottest Portuguese summers.

Storage vessels and tank mixing are pretty straightforward, and changes to them (other than changing the materials they’re made from, or what touches the wine) don’t trigger problems with the rules for the wines’ particular appellations.  Neither does substituting manufactured yeast for natural yeast.  But grape breeding and changes to the yields definitely do. 

Although even many of the most ancient grapes used to make wines are hybrids (like Syrah and Cabernet Sauvignon), most winemaking appellations have strict rules about hybridization.  So while hybrid research for global warming is still relatively new, there will be a time when it becomes an issue for particular appellations if winemakers want to use the new hybrids in their wines.

The same is true for yield increases.  The Portuguese winemaker I spoke with told me that it takes a 20-25% increase in yield to give him the right flavor in some of his white wines.  That high an increase definitely puts his wines outside the yield rules for the appellation.  It’s not that he can’t make the wine that way and sell it – the issue is how he labels it.  In general, wines conforming to the appellation rules and are labeled with a particular D.O. can get a higher price than those labeled as Table Wine.  So he and other winemakers are working with their appellation authorities to see if the rules can be changed to accommodate new climate realities.

Still, if it comes down to making better wine versus labeling it with a higher designation, the Portuguese winemakers I talked to won’t hesitate to go outside the appellation rules.  Particularly since their wines are now beginning to find significant international markets.  “We’ve got a good reputation to maintain and want to keep our production quality consistent,” one winemaker told me.  “I’m not as concerned about what I call the wine, although I hope that the D.O. will agree.”  The French winemakers I spoke with said that they’d ultimately do the same, although for some producers in the Languedoc, they’ve only recently managed to carve out new appellations beyond Vin de Pays.  “We’ve finally recently received recognition of the individual character of our local wines,” according to a Languedoc winemaker.  “Of course we want to preserve that character, I just hope we can do it within the rules we worked hard to get implemented.”


No recipe this time.  Cy and I are undergoing home renovations and we’ve been without a kitchen.  Once I’m back to cooking it’ll make me think more about making food.



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1 Response to Winemakers fight global warming with science and tradition

  1. Pingback: Terroirist: A Daily Wine Blog » Daily Wine News: Good But Not Great

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