It's no secret that California is the beating heart of the American wine industry. Its vast vineyards have been producing exquisite wines that grace tables worldwide for decades. But recent years have seen a dramatic change in the landscape of California wine production: wildfires.
In the past five to ten years, these destructive blazes have become more frequent and severe than ever before. Vines and grapes are especially vulnerable, not just to direct fire damage, but also to smoke taint.
The smoke and ash produced by wildfires contain a chemical – guaiacol – that can alter the flavour profiles of grapes, resulting in an ashy aftertaste in wine made from affected fruit.
While wildfires in arid, forested states like California are natural occurrences, global warming has drastically increased their frequency and severity, leading to a much greater risk of smoke damage.
The scale of the problem
In 2017, California was struck by a wave of wildfires that destroyed well over 100,000 acres in Napa and Sonoma counties. These two counties are some of best known for their wineries and vineyards, and the fire damage to vineyards was estimated at $85 million.
In 2020, the situation is even worse – California has suffered from over 4,000 separate wildfires, which have burned more than twice as much acreage in Napa and Sonoma counties than in 2017. Over 363,00 acres were burned, six people killed, and 1,500 buildings burned to the ground.
The fire damage itself was bad enough, but the blazes created a thick pall of smoke that blanketed vineyards and wineries up and down the coast. The smoke is particularly damaging to grapes, as it can cause a phenomenon called “smoke taint”, in which the grape juice has an unpleasant smoky flavour that taints the wine made from them.
This means that grapes grown in areas up to 100 miles away from the wildfires may be unusable, and can lead to a drop in production. Even after the smoke has cleared, vintners need to check grape samples for smoke taint during fermentation before deciding whether or not they will be able to use them.
Wine that tastes like “fecal plastic”
Because the presence of guaiacol isn’t always easy to spot with a simple taste test, and often only shows up after fermentation, wineries turned to lab testing to identify affected grapes.
Unfortunately, testing for guaiacol and 4-methylguaiacol, the most common smoke taint compounds, is expensive and complex. It can also take weeks to get results from a laboratory.
After the Californian wildfires in 2020, labs had a 43-day backlog for analysis, which is just far too long for wineries facing an immediate harvest.
The effect of smoke taint on a wine’s quality can vary greatly depending on the amount of smoke present and the duration of exposure, but it can cause unpleasant flavours and aromas, such as bacon fat or plastic. Some have even reported that wines with high levels of guaiacol can taste like “fecal plastic”
Rather than wasting time creating wines that are potentially tainted, and with no recourse to fast-turnaround lab testing, wineries were forced to dump corps to the tune of $3.7bn
How has the industry responded?
Currently, the California wine industry, and others in France, Australia, Greece, Italy, and other counties impacted by increasing wildfire activity, are now investigating potential solutions to the issue.
These range from specific sensors in a vineyard that can detect the phenols released by smoke and determine if a crop has become tainted, to a form of chemical ‘sunblock’ that could prevent certain chemicals from passing into the grapes.
A naturally occurring clay, called kaolin, which is already used to protect fruit crops from insects and sunburn, is being tested as a potential solution for vineyards to protect their grapes from smoke-tainted fruit.
Some winemakers are choosing to remove the tainted grapes from their crop, while others are attempting to find ways of using them in lower-end wines or blending them with non-smoke-affected fruit.
Wineries are also testing methods to remove the unpleasant aftertaste of smoked tainted grapes using membrane filtration and filtering using milk proteins and charcoal, although this also removes some of the flavour and aroma compounds that make a wine unique.
Reverse osmosis and spinning cone treatment can also remove the taste of the smoke-tainted compounds, but unfortunately, the smokey smell is actually caused by interactions between phenols and enzymes or bacteria present in saliva.
While these possible solutions are being trialled, no easy fix has yet to be found, and wineries continue to call on governments globally to do more to tackle the climate change that has precipitated the increased risk of wildfires.
On a positive note, the industry has shown tremendous resilience in the face of adversity, with many producers and winemakers working together to share resources, knowledge and ideas to try and mitigate losses.
This spirit of collaboration is just one example of how California’s wine industry has continued to thrive despite these challenges.