Home Wine Industry Spotlights Hope for Stuck Fermentations in the Challenging 2022 Harvest Season

Hope for Stuck Fermentations in the Challenging 2022 Harvest Season


The historically high heat spike in early September resulted in an unusually high level of dehydrated fruit in what was otherwise looking to be a bumper crop in Northern California. Estimates indicate the raisening of 20%-30% of the grapes, which means 20% or 30% lower tonnage. This accelerated raisening led many wineries and vineyard managers to harvest early to avoid the rain.

“If it should have been 22-26 Brix and now it’s over 30 Brix, that’s a big difference, and there are reports of juice reaching 40 Brix or more, with VA’s over 1 g/l,” says Bryan Tudhope, Founder and CEO of VA Filtration. “People are coming to me asking, ‘How are we getting vinegar in our grapes?” 

Tudhope adds, “I can’t explain how, but I can say that excess vinegar in the actual fruit out on the vine is unusual. Fruit typically comes in at 0.2 g/l or less; instead, it’s at 0.8 g/l or more. We’ve never seen levels this high before. Winemakers used to seeing a pH of 3.4-3.8 are now routinely seeing levels of 3.9 and higher, and this is likely to continue as the drought progresses.”

These extreme temperatures, combined with drought, are very stressful for the vineyards. Crops coming in with very high vinegar and sugar levels is a tricky combination that requires rehydrating the juice to reduce the sugar levels so it will ferment. But the high vinegar levels, even with dilution, can lead to stuck fermentations.

There are no current filtration methods for reducing VA in unfermented juice. Rehydrating the juice to a more acceptable 26 brix will reduce the VA if it is high. Starting the ferment at that point and getting it at least 75% or more of the way through will reduce the sugar level to the point that allows VA reduction to take place.

Conditions like these are when Tudhope’s company, VA Filtration, gets involved, using its nanofiltration technology to help winemakers avoid or restart stuck fermentations. The pressure-driven membrane process addresses volatile acidity (VA) by removing acetic acid and Ethyl Acetate (EA) in a water/alcohol stream called permeate while holding back the desirable acids, then re-combining the treated water/alcohol stream with the wine.

VA Filtration is a global filtration technology leader in the US and Chile, with more than 20 years of experience in the wine and cider industry. Its patented mobile filtration results from constant innovation in the membrane technology field and allows the team to move quickly to help winemakers improve wine quality and add value by removing alcohol, undesirable compounds, turbidity, and taints on site. 

When he’s called to a winery to help with a high VA in the juice, Tudhope tells winemakers that it isn’t the end of the world. His advice is, “don’t ignore it because it won’t go away, and don’t dump your fruit on the floor, because you can still make wine out of it. We want winemakers to know that if you get a stuck ferment there are processes for getting it started again.”

A winemaker with a stuck ferment must determine whether the problem is high vinegar, high alcohol and/or high pH before VA Filtration can help get it restarted. While it’s difficult to recommend a set protocol for this process since winemakers have their own ideas about how to do things, settling the stuck wine is the first and most critical step. Dirty wine with RS won’t go through the filtration membranes, so winemakers need to press it off and let it sit for at least a day or two to bring the turbidity down to a manageable threshold for VA reduction or alcohol reduction to happen. Once the VA and/or alcohol levels have been reduced sufficiently, the restart process can be implemented.

2022 is another challenging year for wineries, which is becoming the norm as misfortunes of nature like smoke taint from wildfires, worsening drought, inopportune heat waves and cold snaps confront them. In these difficult circumstances, VA Filtration’s exceptional ability to help winemakers deal with VA reduction, smoke taint removal, stuck fermentations, pH adjustment and other issues makes it a vital partner.

For more information or help with stuck fermentations, contact [email protected] or visit VA Filtration at WIN Expo booth 513 to discuss your challenges and your options for solving them.

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