Grapes and Wild Fires

Smoke has caused a lot of damage to the 2020 grape harvest in California, Oregon and Washington during the past few weeks.  In some cases production has been reduced by over 80.  The smoke can be absorbed right into the grapes’ flesh giving them the flavour of a wet ash tray.

Atmospheric smoke has blocked the sunlight that is essential for the grapes to properly ripen. Poor air quality is slowing harvesting as fieldwork hours are being limited and particle-filtering masks are in short supply due to the coronavirus pandemic.

Wineries were already facing great financial strains due to the reduction in restaurant traffic and smaller crowds visiting vineyards for tastings.  Many tasting rooms remain closed due to fire and smoke risks, while grapes may be damaged or totally ruined.

Oregon, Washington and California together produce about 90% of all U.S. wine. The true impact on the $70 billion industry will not be known for months as crop damage can vary greatly.

Smoke has blanketed much of the U.S. West as fires have charred some 2 million hectares.

Laboratories that test grapes for smoke contamination are being overwhelmed with some taking up to a month to return results, instead of the normal week. Vineyards need this data to determine whether or not to harvest their grapes.

Winemakers and scientists are still learning how smoke can affect wine grapes and how the effects can be mitigated.  Australia has been at the forefront of the research, but studies at American universities have ramped up over the past five years.

The Australian Wine Institute has come up with a few practical ways to manage smoke-exposed grapes.  These include:

  • Hand harvest fruit to minimize breaking or rupturing of skins
  • Exclude leaf material to limit smoke-related characteristics
  • Maintain integrity of harvest fruit, avoiding maceration and skin contact
  • Keep fruit cool to extract less smoke-related compounds
  • Whole bunch press to reduce extraction of smoke-derived compounds

If corrections cannot be made, smoke taint will add two distinct compounds to wine: guaiacol (commonly called Creosote) and 4-methyl guaiacol.

White wines are often more susceptible to smoke than reds. Low levels of smoke can mask the fruit and give a dirty finishing flavour and higher levels negatively affect the smell and taste ashy.   Washing grapes with water might help get ash off the grapes but it does not reduce smoke compounds in the fruit.

It is too soon to judge how the wildfires will impact 2020 vintages but harvested grape supplies are expected to be much smaller.  With smaller harvests winemakers are expected to buy bulk wine from the 2019 season for blending with what is available from this year.

The reduced supply will most likely increase prices making U.S. wines less competitive in the international wine market for the next couple of years.

Sláinte mhaith

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