March 2020 - 27

The scientists took cabernet
sauvignon grape samples from each
vineyard to a local lab to be analyzed
for guaiacol and 4-methyl guaiacol,
then made 27 small batches of wine
from the samples. The cabernet
sauvignon wine samples were sent to
the Australian Wine Research Institute,
which analyzed the wine for volatile
phenols and glycoside compounds.
" The volatile phenols guaiacol and
4-methyl guaiacol are detected in
the fruit by gas chromatography, so
it is possible to sample fruit before
harvest to make picking decisions, "
McGourty said. " Based on our study,
berry sampling and guaiacol/4-methyl
guaiacol analysis are useful for a
quick evaluation of whether or not
fruit from a particular vineyard may
have the presence of volatile phenols
that can potentially result in smokeaffected
wine. "
Testing the fruit for volatile
phenols and glycosides is both
expensive and not completely
predictive as standards are not well
defined for damage based on smoke
chemical concentration, he cautioned.
some vineyards close to the edge of
fires and immediately downwind
were heavily affected, with the grapes
containing high concentrations of the
smoke flavor-causing compounds. But
they determined elevation was not a
factor in smoke flavors in wines.
Wind direction and speed,
temperature and vineyard proximity
to active fires are highly likely affect
whether there will be smoke damage
to the fruit, their research showed.
" Smoke generated in the first one
or two hours from a wildfire is most
damaging to nearby vineyards, "
McGourty said. " Even though a
vineyard may be enveloped in smoke,
if the source of the smoke is from
a distant fire, it will probably won't
seriously damage the fruit quality
because most of the volatile gases
are gone. "
Lake County Winegrape
Commission's Sommerfield said,
" Today, the results of this study
are already proving to be useful
in deepening our understanding
of smoke and the risks it poses to
grapes and wine, in enabling grape
growers and winery buyers to engage
in fruitful discussions and make
informed decisions, and, in turn, in
helping to propel the development of
industry standards and protocols. "
" This is a great little study, the first
one that I know of that takes a systems
approach to evaluating the effects of
wildfire smoke, " McGourty said. FGN
Ryan Keiffer, technician at Hopland Research
& Extension Center, makes wine to see if
grapes exposed to smoke create smoke
flavors. Photo: University of California
®
The Grower's Advantage
Since 1982
Glenn McGourty crushed grapes that
were exposed to River Fire smoke at UC
Hopland Research and Extension Center.
Photo: University of California
These two compounds aren't the only
ones that cause smoke flavors. More
than 70 other compounds in forest fire
smoke can also produce undesirable
flavors and odors described as " like
licking an ash tray, burnt garbage, a
burnt potato, a campfire that has been
drenched with water. "
The taste test
To assess the levels of the compounds
that produce the off-flavors, Oberholster
convened a panel of 14 wine industry
professionals to taste the sample wines.
The wine tasters detected stronger offflavors
in the wines made from riper
fruit, which also contained higher
concentration of smoke compounds.
Less than 6 micrograms per liter of
the smoke compounds were difficult
for the tasters to detect, leading the
researchers to conclude they will have
a minimal effect on wine quality.
Smoke from a distant fire
The scientists also looked at the
influence of distance from the fire and
elevation on smoke taint. They found
Effective Plant Nutrients and Biopesticides
to Improve Crop Quality & Yield
ORGANIC
Contains Auxiliary Soil & Plant Substances
®
ORGANIC
Plant Nutrients & Adjuvants
Botector
Biofungicide
®
Gargo i l
Blossom Protect™
Bactericide
®
Insect, Mite & Disease Control
®
®
Herbicide EC
For more information, call (800) 876-2767 or visit www.westbridge.com
FGN | MARCH 2020 | 27
http://www.westbridge.com
March 2020

Table of Contents for the Digital Edition of March 2020
