The Crush July 2022 - 1

the Crush
Volume 49 | Issue 7 | July 2022
Winegrape Smoke Exposure
Article by Ted Rieger
The West Coast Smoke Exposure Task Force (WCSETF)
and researchers funded from a multi-year U.S.
Department of Agriculture (USDA) Specialty Crop
Research Initiative (SCRI) grant have provided progress
reports and new information (highlighted below)
through webinars and presentations this year on efforts
to understand and mitigate the impacts of wildfire
smoke exposure on winegrapes and wines in West
Coast vineyards.
WCSETF researchers are installing sensor stations
in California, Oregon and Washington vineyards to
monitor smoke density and composition that will be
paired with weather stations that monitor temperature,
humidity, wind speed and direction. The sensors will
measure particulate matter (PM) levels at PM 1.0, PM
2.5, and PM 10, and air quality/pollutant chemicals
such as carbon monoxide (CO), carbon dioxide (CO2),
nitrogen dioxide (NO2), ozone (O3), sulfur dioxide
(SO2) and volatile organic compounds (VOC).
Tom Collins at Washington State University (WSU)
has field tested sensor stations in Washington since
2020 and plans to have 20 in operation during 2022.
In California, UC Cooperative Extension Enology
Specialist Anita Oberholster will initially set up one
station at the Oakville Experimental Station, and one
at the Robert Mondavi Institute vineyard at UC Davis
by the end of July. Stations are planned for installation
in 2022 in Napa and Sonoma Counties in cooperation
with vineyard owners with sites at different
elevations, AVAs and with a focus on sites with
Cabernet Sauvignon, Chardonnay,
Pinot Noir and Sauvignon blanc. At
each sensor location grape samples
will be taken and analyzed each
season (whether smoke exposed or
not) to correlate with recorded data. The researchers
will work with atmospheric scientists to analyze data
and develop programs to model smoke exposure risk.
Obersholster will also begin experiments this year at
Oakville Station in a plot of 160 Cabernet Sauvignon
potted vines using a controlled smoke chamber to
expose grape leaves to different smoke levels and
evaluate whether smoke metabolites can be absorbed
and translocated from grape leaves to grape clusters.
This trial plot will be used in a later trial to evaluate the
effectiveness of barrier sprays such as kaolin (Surround)
and bentonite in protecting grape berries from
absorbing smoke compounds.
Test plot of 160 potted Cabernet vines at UCD Oakville Station to be
used for smoke exposure trials. (Photo: Ted Rieger)
Volatile phenol (VP) smoke impact compounds
known and analyzed in labs as smoke taint markers
to date include: guaiacol, 4-methylguaiacol (4-MG),
4-methylsyringol, syringol, p-cresol, m-cresol, o-cresol,
phenol, 4-ethylguaiacol and 4-ethylphenol. VPs occur in
both free and bound form. Bound VPs can be released
from wines through a reaction with human saliva during
tasting and be perceived as smoke taint.

The Crush July 2022

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