Mezcal acidity: what it is, where it comes from and what it reveals
Mezcal acidity is the amount of organic acids that make it into the bottle, mostly acetic acid. It forms at two moments: when the agave is roasted and when the mash ferments. In the right measure it brings freshness and helps build fruity aromas; in excess, the mezcal smells like vinegar. That makes acidity one of the best clues to how a palenque works.
Which acids are in mezcal?
The main one is acetic acid, the same acid found in vinegar. A 2025 study of artisanal mezcals from Oaxaca measured 75 to 409 mg per 100 mL of anhydrous alcohol, depending on the agave and the batch (Sánchez-Fernández et al., Foods).
Smaller amounts of fatty acids such as capric (decanoic) and lauric (dodecanoic) acid also appear, and they vary with agave species and region (Vera-Guzmán et al., Beverages, 2018).
Where does the acidity come from?
| Stage | What happens | What it adds |
|---|---|---|
| Roasting | Heat transforms the agave's sugars (Maillard reaction), releasing acetic acid and furfural. | Toasted notes and the first dose of acidity. |
| Fermentation | Native yeasts and bacteria work together. Lactic acid bacteria lower the pH and some produce acetic acid. | Complexity, stability and most of the acidity. |
| Distillation | Acids concentrate in the last fractions, the tails. | The master distiller decides how much acidity goes in with the cut. |
Methanol, ethanol and acetic acid already appear during roasting (Vera Guzmán et al., Revista Fitotecnia Mexicana, 2009). The same study measured juices at pH 4.5 (Espadín, A. angustifolia) and 5.5 (Tobalá, A. potatorum).
In fermentation, a 2026 study of four Oaxacan palenques identified six bacterial genera, including Lactiplantibacillus and Leuconostoc. They produce acids that lower the pH and stabilize the ferment (López-Sánchez et al., Fermentation).
How does it affect flavor?
Acidity isn't good or bad on its own. Part of the acids react with alcohol to form esters, the compounds behind fruity and floral notes. The rest stays free and adds freshness.
The problem starts when fermentation runs too long or gets contaminated: acetic acid takes over and the mezcal smells of vinegar or nail polish remover. That's a flaw, not a style.
How is it measured, and what does the standard say?
Acidity is reported as acetic acid in mg per 100 mL of anhydrous alcohol, that is, calculated on pure alcohol rather than on the bottle, so mezcals of different proof can be compared.
Mexico's original mezcal standard, NOM-070-SCFI-1994, set a maximum of 170 mg. The current standard, NOM-070-SCFI-2016, no longer lists total acidity in its specifications table; it does limit methanol (30–300 mg), higher alcohols (100–500 mg), aldehydes (up to 40 mg) and furfural (up to 5 mg).
How is it controlled at the palenque?
- Clean vats, so acetic bacteria don't take over.
- The right fermentation time: the mash is distilled when fermentation ends, not days later.
- A good tails cut during distillation, where acids concentrate.
How it applies to ZUNTE
At ZUNTE, espadín agave harvested at about 8 years is roasted for 4 days in a conical stone oven, milled with a tahona, fermented for 12 to 15 days in wooden vats with crystal-clear water and double-distilled in a copper still over 35 hours. The goal is a mezcal with light smoke, herbal and citrus notes and a clean finish: acidity that brings freshness, not vinegar.
FAQ
Is it bad for mezcal to be acidic?
No. Moderate acidity adds freshness and builds fruity aromas. It's only a flaw when the mezcal clearly smells of vinegar.
Which acid dominates in mezcal?
Acetic acid, born in the agave roast and in fermentation.
Does NOM-070 limit mezcal acidity?
The 1994 version capped it at 170 mg of acetic acid per 100 mL of anhydrous alcohol. The current 2016 version doesn't include that parameter in its specifications table.
How does a master distiller keep acidity in check?
With clean vats, a fermentation that doesn't run too long and a good tails cut during distillation.
Sources
- NOM-070-SCFI-2016, Alcoholic beverages—Mezcal—Specifications (DOF)
- NOM-070-SCFI-1994 (text at Mezcal y agaves)
- Sánchez-Fernández et al. (2025), Foods 14(7):1222
- Vera-Guzmán et al. (2018), Beverages 4(1):9
- Vera Guzmán et al. (2009), Revista Fitotecnia Mexicana
- López-Sánchez et al. (2026), Fermentation 12(2):89
