Rod Byers: Effects of smoke on California wine harvest |

Rod Byers: Effects of smoke on California wine harvest

At first glance 2020 appears to be an excellent grape growing year delivering a superlative harvest.

Ample rain last winter provided deep watering for the roots. Once the growing season started there were no calamities to speak of; no late frosts or soggy spring weather; no hail shredding tender leaves; no rain at flowering.

Generally, daily temperatures were moderate. Heat spikes in mid-August and early September were concerning but not devastating. Harvest started quite typically in late August with early whites like Sauvignon Blanc.

If it were any other year than 2020 I would be commenting on a great harvest and the anticipation of some terrific wines. But this is 2020, and like everything else that has gone haywire, beauty in this year’s harvest may only be skin deep.

Smoke taint occurs when grapes are exposed to wood smoke. When wood burns it releases aroma compounds called volatile phenols. These phenols can permeate the grape skins and bond with the sugars inside to form molecules called glycosides.

The wildcard on the table, the big unknown, is something called smoke taint. Anybody who has been living in Northern California over the last six weeks knows we have been living in a sea of smoke. The question is how is that going to affect the grapes?

Smoke taint occurs when grapes are exposed to wood smoke. When wood burns it releases aroma compounds called volatile phenols. These phenols can permeate the grape skins and bond with the sugars inside to form molecules called glycosides. Even yeast can’t do that.

The process is called glycosylation. Here is the insidious part. When the glycoside molecules form they hide their smokiness. Smoke taint cannot be detected by smell or taste in fresh grapes.

Once the grapes are fermented the wine’s natural acidity breaks the glycoside bond making the phenols volatile, think smell-able, again. It is only after the grapes have been fermented that it is possible to know the extent, if any, the grapes have been affected by smoke.

Smoke taint research is relatively new in California getting kick-started with the devastating fires of 2008. The tragic 2017 wine country fires occurred in November after 90% of the grapes had been harvested. Smoke has no effect unless the grapes are still on the vine.

The 2020 fires started in mid-August when the grapes were still hanging. The current thinking is that for grapes to be damaged the fires must be close and the smoke fresh. At that point it does not take long, as little as 30 minutes, for grapes to become affected.

The more distant or second-hand the smoke, the less potent but nobody knows how much less or how distant?

For California growers it creates a perfect storm of calamities. Insurance companies are not honoring crop insurance smoke claims without a certified smoke taint lab report. On the other side wineries are opting out of grape contracts unless they get a smoke-free certification.

At the beginning of September ETS Laboratories in St. Helena was one of the few labs doing smoke tests and they were already backed up to the end of September by then. The Glass Fire forced them to evacuate their St. Helena lab while the smoke taint threat only worsened.

That puts enormous pressure on the grower. With no way to get a timely certificate they can pick and have the grapes rejected or not pick and chance having an insurance claim rejected, if there’s crop insurance in the first place.

To make matters worse for the growers the entire wine supply chain is full. There is still a lot of 2019 bulk wine available. Some wineries are choosing to simply fill their tanks with bulk from last year.

Meanwhile winemakers up and down the state have been picking 50 or 100 pounds of their own grapes to do mini-ferments, scrambling to see if smoke taint appears from their vineyards.

Certainly, some vineyards will go unpicked but many more will be harvested leaving a string of question marks. Right now, there is a lot of talk about the integrity of the final product. No smoke-tainted wines here. But sooner or later some producer is going to think, this wine’s not that bad.

So, how bad is bad? Most of us have never tasted a wine contaminated with smoke taint so we’re not really sure. It’s ironic. Winemakers go to great lengths to add the flavor of smoky wood to wine. Remember, oak barrels are burnt in their production process.

Lately it has been trendy for some wineries to age wine in old bourbon barrels to generate even more char flavor. So, a little smoke taint, a little natural char, what’s the problem?

Smoke taint can be overpowering, ruining a wine. Any winemaker will tell you there is a huge gap between the nuances of an oak barrel and the acrid char in the back of your throat when standing close to a fire when the wind suddenly changes. Some wines will deserve to be dumped.

We’ll take a closer look next month but right now it does not appear that smoke will be a factor in this year’s Nevada County grape crop. While the air was oppressive at times the fires were probably too far away for negative impact.

If you take the smoke issue off the table then what we’re left with is a really good harvest. When the dust settles or in this case, when the smoke clears, wines from Nevada County may be some of the best things to come out of 2020.

Rod Byers, CWE, is a Certified Wine Educator and wine writer as well as a California State Certified Wine Judge. He is the host of the local television show Wine Talk. He can be reached at or 530-802-7172.

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