Wine & Spirits - June 2020 - 11

on extended skin contact for color and structure. Hand
harvesting is a good first step because it minimizes skin
maceration. Pickers can make sure there are no leaves in
the harvest bins, as these also have smoke compounds
in them. Fruit should be kept cool, because this results
in less extraction, and it's ideal to press the intact whole
bunches. The free run (the first 400 liters per ton from
the press) should be kept separate because this will have
fewer smoke compounds. "These compounds are mainly
in skins," ETS's Hervé says, "so if you prevent skin contact you minimize the problem. This works beautifully
for whites or rosés, but, in our experience, it doesn't work
for reds. The smoke compounds migrate into fermenting
juice extremely quickly. In all the red ferments we have
followed, the maximum number of smoke markers are
already extracted after three days." In fact, shortening the
fermentation with reds can worsen the problem, resulting in a light wine that shows smoke impact more clearly.
There are some other winemaking techniques that
can be used to mitigate smoke impact, but they all have
their downsides. One is to fine with activated carbon:
It's widely used during filtration in water treatment as it
grabs hold of organic materials and removes them. When
applied to wine, since it isn't particularly selective, it has
a negative effect on other aroma compounds. Another
approach has been to use reverse osmosis, coupled with
a technique called solid-phase adsorption. Reverse osmosis takes out a permeate fraction from the wine that contains water, acids, alcohols and chemicals below a certain
molecular point cutoff. This fraction is then treated alone
with solid-phase adsorption to take out the smoke compounds before returning it to the wine. It removes some
beneficial aroma compounds, too, but the hope is that
because just this small fraction of the wine is treated, its
negative impacts will be limited. Yet, while treatment has
been effective in some cases, the smoke impact can come
back. Presumably, some glycosidases remain and are later
hydrolyzed to reveal smoke compounds. So, wines treated
this way should be drunk quickly.
Chris Carpenter of Jackson Family Wines, who makes
the wines of Lokoya, Cardinale, La Jota and Mt Brave in
Napa Valley, has had some experience with smoke impact.
In his experience, different varieties show the smoke differently. "Merlot, petit verdot and malbec were crushed
by it," he says. "Cabernet sauvignon and cabernet franc
fared relatively better." He adds that syrah is a problem for
analysis, "because many of the compounds you are testing for in smoke occur naturally in syrah." After crushing
affected grapes, Carpenter added inactivated yeast hulls,
which are supposed to soak up some of the smoke residue,
but he's not sure whether or not this helped. "At the time,
any of the scrubbing technologies that were available were
not able to scrub bound compounds," he says. "Some of
the companies that are working on that now purport to be
able to deal with more of the bound complexes but there
is no independent science [backing them up]."
One of the difficulties he finds in assessing smokeimpacted grapes is how quickly these compounds affect
your sense of taste and smell. "After two or three wines
that are tainted, your palate is dead and you need to reset
or you lose the ability to taste anything," he says. "We

still do not understand the dynamics of smoke taint, the
compounds and their evolution over time," says Carpenter. "There is no solution yet. If you bottle wines that you
suspect have smoke in them, you are taking a huge risk,"
he says, noting that any grapes that were on the vine during smoke events, even if they don't show any effect, could
show smoke taint in the future. "We ended up scrapping
two-thirds of my inventory from 2017 because the risk of
bottling those wines was too great." He didn't bottle any
Lokoya cabernets in 2017.
Dan Petroski of Napa Valley's Larkmead Vineyards
also has experience processing potentially smoke-affected
grapes. "In 2017, after our own harvest was complete, we
crushed forty tons of grapes (mostly cabernet sauvignon,
with some malbec and petit verdot) for a vineyard client
whose winery was in a quarantined zone. The grapes had
sat through a week of the fires and smoke exposure on the
valley floor of Napa," he recalls. As part of the process,
they did sensory evaluation and chemical analysis along
the way. "Thankfully, the client's grapes did not have perceptible smoke issues from a chemistry or sensory perspective. We don't know why in this particular instance
this is true for us and not for others."
One winery that did end up bottling some wine from
smoke-affected grapes was Anthill Farms in Healdsburg.
This single-vineyard pinot noir and syrah specialist was
impacted by smoke in Anderson Valley in 2008. "We
declassified all the wines, carbon filtered the good lots and
blended them into one wine of about 200 cases that we
sold to our customers with this explanation, I believe, for
$25," says co-owner Anthony Filiberti. "It was good wine,
not amazing. Most people were happy and enjoyed it."
However, some customers complained and posted their
thoughts on various wine bulletin boards. Filiberti says
that he still drinks the wine from time to time, opening
bottles at customer pick-up events. "Some taste pure and
delicious, some taste like barbecue chips."
Research is ongoing as to how grapes ripening on the
vine can be protected from smoke impact. In a scientific
paper published in December 2019, researchers from the
University of British Columbia describe using a biofilm
as an artificial grape cuticle to prevent volatile phenols-
major contributors to smoke impact-from entering the
grape tissue. This biofilm is already used in agriculture to
prevent cracking in cherry skins. The initial results indicate that there is some protective effect on grapes. Dr.
Matt Noestheden, one of the authors, says that they are
working on results from larger-scale field trials, which
should help them assess whether the cost of such a spray
makes economic sense for growers. "Really, it is still early
days on getting a complete picture of if and/or how this
product will help grape growers," says Noestheden. They
have included fermentations and are planning to do sensory work to see whether there is any impact on wine flavor. "The product is already used on blueberries and cherries without any holding period after treatment," he says.
"So, assuming it doesn't have a sensory impact, it would
not need to be washed off after picking." The product is
not currently approved for use on wine grapes, "So that
hurdle would have to dealt be with by the producer," he
adds, "if our large-scale trials play out positively." ■
WINE & SPIRITS

JUNE 2020

Wine & Spirits - June 2020

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