Naked Fermentation: Bidding Farewell to Malic Acid?

In 2010 Rajat Parr tested one of his winemaking theories. He believed sulfur added to newly harvested grapes stripped the subsequent wine’s immunity and aging potential. By blanketing the grapes with protectant, and killing off many organisms, the grapes’ natural immunity is also stripped. A wine would be more whole, longer lived, and complex if the grapes finish native fermentation naked.
Rajat arrived at this notion while studying the Premox problem in Burgundy. In the 1990s, University educated winemakers were taught to play it safe in the winery, and began spraying sulfur on every lot of fruit entering the winery, not just ones that had obvious issues like mold or mildew. Rajat makes his Sandhi Chardonnay in Santa Barbara County where low humidity, high winds, and in-frequent rain eliminates the presence of mold. This may be the best place in the world to experiment with naked fermentations.
Because Rajat crushes his Sandhi Chardonnays alongside Stolpman fruit, Sashi Moorman closely monitored the results. Sashi liked what he saw, and began phasing out sulfur additions at Stolpman.

The Results
While we believe naked fermentations make our wines more dynamic and nuanced for the long haul, we give up some control to Mother Nature. Case in point, left naked, many of our wines begin malolactic decarboxylation during primary fermentation as the bacteria that digest malic acid into lactic acid prosper without sulfur. Lactic acid bacteria are more sensitive to sulfur than Saccharomyces, the yeast responsible for digesting sugar into alcohol.
Our reds and barrel-aged Roussanne and L’Avion go through malolactic decarboxylation every vintage, imparting a round mouth feel. A product of malolactic decarboxylation is Diacetyl, which adds a rich buttery flavor to our oak aged white wines. Naked fermentation should allow the already age-worthy L’Avion to shine even longer due to elevated immunity.

2013 Sauvignon Blanc: Naked and Ready!
Traditionally, we add sulfur to Sauvignon Blanc fruit to inhibit malolactic decarboxylation. Without sulfur, the 2013 Sauvignon Blanc went through malolactic decarboxylation and therefore has a nice richness to it, along with the bright limestone-driven minerality and lemon-lime fruit profile we have all grown to love.
Because the wine has already gone through malolactic decarboxylation, we don’t need to add sulfur to prevent it from happening in bottle and creating a spritz, nor do we have to filter as finely to remove lactic acid bacteria. The smooth, weightiness of lactic acid along with the lack of sulfur combine to allow the wine to be enjoyed extremely young. Lactic acid is more stable than malic acid, and the wine should age quite a few years!

2013 Viognier and Rose: Not goodbye forever, Malic Acid!
Because Viognier is relatively low in acid compared to Sauvignon Blanc, we expected malolactic decarboxylation to complete before the end of fermentation. Lactic acid bacteria usually like higher pH conditions. But leaving fermentation up to native yeasts, malolactic decarboxylation only completed partially, leaving both malic and lactic acid. Sashi tasted the combined wine and loved it. The malic acid keeps the fruit-forward varietal restrained, rather than blousy. We were careful to filter and add sulfur before bottling to make sure the wine doesn’t mutate in bottle.
Likewise, malolactic decarboxylation only partially completed in the 2013 Rose and the results pleased Sashi. The lactic acid grants smoothness and depth to red-hued wine while the malic acid ensures a crisp, refreshing pop on the finish to keep the wine light on its feet.

The Results of Naked Fermentation
The 2013 Viognier and Rose demonstrate that if we continue to ferment naked, depending on the lot, we can still make wines with malic acid. There won’t be a black and white shift in profile in our tank fermented white and pink wines although we expect all of the wines to have some lactic acid.
What the 2013 harvest proves is that naked fermentation is certainly only for the highly adaptable and experienced boutique winemaker. Fermenting both naked and native, Sashi will adjust his blending, post-fermentation sulfur additions, and filtration levels based on how far malolactic decarboxylation completes in each lot.
Commodity wineries aiming to produce a homogenous product every year should continue to playing it safe: dousing sulfur on the fruit and inoculating to control fermentation.

No Sulfur before Fermentation: Thanks to the Vineyard
At the end of the day, we can push the limit of terroir expression through naked fermentation only because of our vineyard site. The grapes arrive without any trace of fungus and the organic grapes are otherwise healthy.
Stolpman Vineyard’s terroir and Ruben’s meticulous farming allow Sashi to make wines nakedly.