Does Mezcal Go Bad?

Does mezcal go bad? Or more specifically, does mezcal in an opened bottle eventually go bad? We’ve seen several threads on Facebook, Reddit, and elsewhere over the years that have asked this question. Some have posited that oxygen or oxidization would have a negative impact on the spirits over time. Others have referred to results of scotch or whiskeys changing drastically if not consumed within a reasonable amount of time after opening. Opinions on the subject tend to vary greatly, but there seem to be three main positions that people take:

1. Mezcal left in a bottle that has been opened will stay the same or actually improve
2. Mezcal left in a bottle that has been opened will improve to a certain point, but then go bad if there is too little mezcal left in the bottle
3. Mezcal left in a bottle that has been opened will eventually go bad

Our friend Mezcal PhD tells us that mezcal will likely improve over time. He says;

“If you open your bottles once a year or so and let new air in (assuming you did not drink it all), the mezcal will improve over time. Acetaldehyde is present in a distilled mezcal. When exposed to air, this oxidizes to acetic acid, which is ester. We love esters in spirits because they are associated with positive smells and flavors like banana, pineapple, and sugar. By letting fresh air in every year or so, you are re-energizing the process.”

According to him, there’s some sound science to the fact that mezcal would change over time, but we wanted some experiential evidence that it would indeed change for the better.

We also asked co-founder of Mezcal Vago, Judah Kuper, the same question last year. His answer was similar to Mezcal PhD in that he believed that mezcal improved after the bottle was opened. His theory was that mezcal would continue to improve until the bottle would get down to about 25% full, at which time he suggested that you should just drink the remaining mezcal because it would start to drastically change (presumably for the worse). This belief seems to be held by many in the industry, and we’ve spoken to several users of this website who prefer to re-bottle their mezcal to a smaller glass bottle (like a dram or something similar) once the original bottle gets below that 25% threshold. This seems to vary pretty widely, but many have a tradition or practice for dealing with low bottles.

Mezcalero No. 14 intentionally left for seven months with very little remaining in the bottle.

Still other members of this website have written to us about noticing significant differences in older opened bottles, which they’ve posited was due to oxidation and/or evaporation. Does oxidation or evaporation make them worse or just different? Generally, we’ve found that older bottles tend to mellow and get better over time. But is this true for bottles that are less than 25% full? We pulled a few lower ABV mezcals off the shelf earlier this year. They’d each been open for over a year with about 25% of the bottle left. Unfortunately, they didn’t taste very good, but maybe they weren’t really all that enjoyable to begin with?

While questions about the aging of mezcal in opened bottles is an active debate, the community seems decided on the aging of mezcal in closed (never-opened) bottles and/or in larger glass demijans. For those unfamiliar with the Aged-in-Glass or Madurado style, this refers to the aging of mezcal in glass after it is distilled. Some releases will be aged in glass for upwards of two or three years before being bottled for sales and general consumption. You’ll often see special prized batches of mezcal aging in glass at palenques around Oaxaca.

Aging in wooden barrels, which is done widely for whiskey and tequila, is less common in Mezcal. Barrel aging typically removes the more vegetal notes of the agave and replaces them with notes of the wood, like caramel, brown sugar, or vanilla. Aging in glass, however, imparts no new flavors. While the flavor of the mezcal does indeed change as it ages, the aging in glass tends to enhance what is already present, making the mezcal more balanced, integrated, and settled. The growing popularity of mezcal that is aged-in-glass clearly emphasizes the importance of time on how distilled agave can settle and build structure long after it has left the still. So we know that time can play an integral role in improving mezcal, but what about other elements, like the amount of air in the bottle and the oxygenation and/or evaporation process that occurs when there’s very little mezcal left in the bottle?

Rather than pontificate, we decided to do some hard core research. On March 19, 2019 we selected four of our favorite bottles. They had all been open for a little over a year and all the bottles had just over 25% left. We poured the four bottles of mezcal into smaller air tight 250ml glass containers. In the original bottles, we left about 2-3oz of mezcal to interact with the air left in the bottle. Our theory was that the air in the original bottle would have some impact on the aromas, flavor, and complexity of the mezcal over time. Would this impact be good or bad? We weren’t sure.

So on October 18, 2019 (seven months later), we performed a blind tasting, where we compared the original bottle with excess-air with the no-air re-bottled mezcal.

Mezcalero No. 14 (notice levels in each bottle)

Mezcal Vago Elote

> No-air (preferred)

“Soft sweet clay. Sour on the back end. Hints of white grape juice.” — Tyler

“Aromas of peanut butter cups, woody, leather.” — Chris

“Aromas of cinnamon, all spice, sandalwood, and vanilla. Flavors of cinnamon, sand, and slate.” — Jonny

> Excess-air

“Notes of clay. Robust. No sour finish. More notes of dates and hickory.” — Tyler

“Less pungent on the nose. Slightly muted flavor notes but mostly the same.” — Chris

“Muted aromas. Much softer and bit lighter on the palate. Similar tasting notes but less pronounced. More mellow but less exciting.” — Jonny

Overall, the Mezcalero No. 14 had slight differences from the different aging. We noticed this more on the nose than on the palate, with more of the aromas in the No-air mezcal being more pronounced and bold. We all preferred the No-air mezcal as it was a bit bolder and held a strong punch with it’s various notes and characteristics.

> No-air

“Notes of white pepper, salt, corn nuts. Strong finish.” — Tyler

“Nose has notes of maple syrup and pancakes. Strong tastes of alcohol.” — Chris

“Strong aromas of corn, a bit of nail polish, coffee, and maple pecan. Tastes of grilled elote. Very sweet. A bit of nail polish on the palate as well.” — Jonny

> Excess-air (preferred)

“Strong notes and aromas. Very little difference between the two.” — Tyler

“Similar notes on the nose but more like cornmeal than pancakes. More mellow.” — Chris

“Still strong aromas. Very similar, but more mellow and balanced.” — Jonny

Overall, the Vago Elote showed slight differences between the two aged mezcals, but we all agreed that we preferred the Excess-air mezcal. It was much more mellow and all of the nail polish/alcohol notes had vanished over time, making this an incredibly rounded and balanced Elote.

Rey Campero Tepextate (notice levels in each bottle)

El Jolgoio Barril

> No-air

“Candied peppers, Dr. Pepper, and Jelly Beans. Short finish.” — Tyler

“Lavender flavors, a bit of alcohol present. Short finish. ” — Chris

“Strong notes of green pepper, coffee, jalapeno, lavender, and mint. The palate is like a basket full of fresh peppers. Stronger aromas on this one, but very short finish.” — Jonny

> Excess-air (preferred)

“Cinnamon, cotton candy, lingering pepper jerky finish.” — Tyler

“More mellow nose and aromas. Notes of chocolate, rose pedals. Long finish.” — Chris

“Lighter nose and more creamy notes and vanilla on the palate. Much softer and more delicate than the first.” — Jonny

Overall, the Rey Campero Tepextate was our favorite from the evening. While that has nothing to do with aging, it’s worth noting that this stuff remained stellar. We all agreed that the finish on the Excess-air mezcal was much longer and more pronounced. The finish on this actually extended and was enhanced by the presence of the air in the bottle. Like the Elote, the Excess-air mezcal was our favorite for the Rey Campero Tepextate.

> No-air

“A bit funky with some burnt notes on the back of the palate.” — Tyler

“Notes of ash and firewood on the nose and palate.” — Chris

“Alcohol on the nose. Palate has beets and root vegetables with a bit of cigarette ash.” — Jonny

> Excess-air (preferred)

“Very similar but more mellow with fewer of the burnt notes present.” — Tyler

“Almost identical nose and palate but a bit more blended in flavor.” — Chris

“Softer nose. Softer palate. More balanced and mellow.” — Jonny

Overall, the El Jolgorio Barril showed slight differences between the two different aged mezcals. Like the Vago Elote and the Rey Campero Tepextate, we all found that the Excess-air was our preferred option among the two.

We weren’t sure what to expect from this tasting, but we’d hypothesized that the air in the bottle would indeed have some impact on the mezcal after seven months. In the end, we found that our hypothesis was correct. Generally speaking, the Excess-air mezcals were all much more mellow and balanced than those that had been resting in a bottle with little/no air. Of the four mezcals included in this tasting, we preferred the Excess-air mezcal for three of them.

While this is encouraging news for people (like us) who have dozens of bottles open at any given time, it’s intriguing that the Mezcalero No. 14, which is an incredible mezcal, was the only bottle that we preferred with little/no air. It was the only mezcal in the group that was distilled in clay. It also had marginally lower ABV than the others. Could one of these factors have made the difference? That’s a question for a future tasting.

For now, it seems safe to say that your mezcal will not go bad from having too much air in the bottle. In fact, as Mezcal PhD had posted, the air appears to help your mezcal become subjectively more enjoyable over time. What’s your ritual for keeping mezcal after the bottle is opened (assuming you don’t just drink it)? Have you noticed differences in bottles that have been open for extended periods of time? Are your mezcals getting better as they age?