Mezcal & Tequila

Agave Botany: The Monocarpic Succulent

Agaves (family Asparagaceae, subfamily Agavoideae, genus Agave) are monocarpic succulents — they flower once, then die. This life history is central to agave spirit production: the plant accumulates carbohydrate reserves (primarily fructans) in its central heart (piña) over 7–30 years before producing a flowering stalk (quiote). Distillers harvest the piña at the optimal point before the quiote emerges — harvesting too late means the plant has converted its fructan reserves into the quiote, reducing fermentable sugar content and spirit yield.

The genus Agave comprises approximately 200 species native to the Americas (Mexico, Caribbean, southern US, Central and South America). Of these, Mexico has the richest diversity — over 150 species — and uses approximately 40 in certified mezcal production. The taxonomy is complicated by regional naming: a single species may have dozens of local names (nombres comunes), and the NOM-070 appendix lists both scientific names and permitted common names for certified agave use in mezcal.

Fructan Chemistry: The Agave Carbohydrate

Unlike cereal grain (which stores carbohydrate as starch, a glucose polymer) or sugar cane (sucrose), agave stores carbohydrate primarily as fructans — specifically agavins, a complex branched-chain fructan unique to agave. Agavins are not hydrolysable by human digestive enzymes (making them a dietary fibre), but heat and acid break them down into fermentable fructose and some glucose during the piña cooking process.

Key Agave Species for Mezcal

The NOM-070-SCFI-2016 permits the use of over 40 agave species for certified mezcal production. Each species has a distinct flavour profile, maturation time, yield, and geographic distribution. The following are the most commercially significant:

Blue Agave — Agave tequilana Weber var. azul

Blue Agave (Agave tequilana F.A.C. Weber var. azul) is the only agave permitted for tequila production under NOM-006. It is named for the steel-blue cast of its young leaves. Weber's classification was published in 1902 by Franz Arthur Constantin Weber, a French physician and botanist who collected Mexican plant specimens. Blue Agave matures in 7–10 years in the Tequila Valley (lower altitude, volcanic soil, warm climate) and up to 10–12 years in Los Altos (higher altitude, red iron-rich soil, cooler). The piñas weigh 35–90kg at maturity. Blue Agave is exclusively cultivated — there are no wild populations of commercial scale — making tequila production entirely dependent on agricultural monoculture, with associated disease risk (most notably the Fusarium oxysporum and related fungal pathogens that have periodically devastated Blue Agave fields).

Tequila: NOM-006-SCFI-2012

The CRT and the NOM System

The Consejo Regulador del Tequila (CRT), headquartered at Av. Patria 723-D, Zapopan, Jalisco 45060, is the third-party certification body authorised by IMPI and the Mexican Ministry of Economy to administer NOM-006-SCFI-2012. Every tequila production facility — from small craft distilleries (fábricas) to large industrial plants — must be certified by the CRT and assigned a NOM number that appears on every bottle produced. The NOM number is a distillery identifier, not a brand identifier: multiple brands may be produced at a single NOM, and a single company may own multiple NOM-registered facilities.

This NOM transparency system is unusual in the spirits world. Consumers can look up a NOM number to identify which distillery produced a tequila regardless of brand name — revealing, for example, that several ostensibly premium "craft" tequilas are produced at the same large industrial facility as mass-market brands. The CRT publishes a public registry of active NOM numbers at crt.org.mx.

Tequila Terroir: Tequila Valley vs Los Altos

Within the tequila DO, two principal sub-regions produce meaningfully different agave and spirit profiles. The differences arise from altitude, soil type, temperature, and rainfall — genuine terroir variation within a single agave species and DO territory:

Tequila Categories by Maturation

Permitted Additives in Tequila

NOM-006 permits the addition of up to four categories of substances in 100% agave tequila (in amounts not exceeding 1g/L total), in addition to the unlimited use in gold/joven mixto: (1) Caramel colouring (colour adjustment); (2) Oak extract (flavour); (3) Glycerin (texture/mouthfeel); (4) Sugar-based syrup (sweetening). The use of these additives is not required to be disclosed on the label in the United States — though some producers voluntarily disclose "additive-free" status. Third-party "additive-free" certification (e.g. Tequila Matchmaker's programme) has grown as consumer awareness increases.

Mezcal: NOM-070-SCFI-2016

The Three Production Categories

NOM-070-SCFI-2016 creates a three-tier production category system that formally recognises the spectrum from industrial to fully traditional production methods:

Pit-Roasting and Smoke Chemistry

The earthen pit horno (horno subterráneo) is the defining technology of artisanal and ancestral mezcal production. A cylindrical pit (2–4m diameter, 1–2m deep) is lined with stones and filled with burning wood and charcoal. When the stones are sufficiently heated (several hours), the fire is reduced, and the agave piñas are stacked on top and buried under fibre mat, earth, and canvas for 3–7 days. The piñas cook via conductive heat from the stones and convective heat from smouldering wood, while absorbing smoke compounds that define mezcal's characteristic flavour.

The smoke chemistry of mezcal has been studied in detail. Vera-Guzmán et al. (2019, LWT — Food Science and Technology 107:198–206) identified the following key phenolic smoke compounds in Oaxacan artisanal mezcal:

Tequila — which uses autoclave or hornos cooking without pit-roasting, followed by column or column+pot distillation — contains very low levels of these smoke phenolics. This is the primary chemical basis for the organoleptic difference between the two spirits. Heavy autoclave cooking can produce cooked/baked agave notes (furfural, 5-hydroxymethylfurfural) without smoke character.

Mezcal DO States and Oaxaca's Dominance

Oaxaca accounts for approximately 85–90% of certified mezcal production by volume. The state's dominance reflects its pre-Columbian agave distillation heritage, its biodiversity (more agave species than any other Mexican state), the concentration of artisanal production knowledge in indigenous Zapotec, Mixtec, and other communities, and its role as the first region to seek DO protection. Key Oaxacan mezcal-producing districts include: Miahuatlán (espadín-dominant, large producers); Sierra Norte (diverse agaves, high altitude); Cañada (tepeztate, tobalá); and the Central Valleys around Mitla and Tlacolula.

Durango and Zacatecas produce mezcal from Agave durangensis (Cenizo agave), which has distinctive earthy, mineral, and sometimes dried-fruit character. Guerrero's mezcal centres on Agave cupreata (Papalometl), producing a more tropical-fruity, less smoky profile. San Luis Potosí is known for Agave salmiana (maguey verde/pulquero) — large agaves that produce mezcal with strong herbal and anise notes.

Chemistry and Technical Reference

Agave Cooking: Autoclave vs Hornos vs Pit

The cooking stage converts agave fructans to fermentable sugars via hydrolysis. The method dramatically affects both yield and flavour. Autoclave cooking (120°C steam pressure, 7–12 hours) maximises fructan hydrolysis efficiency and produces clean, consistent cooked-agave character with furfural and caramel Maillard products but no smoke. Traditional stone/brick hornos (80–100°C convective heat, 24–72 hours) produce similar hydrolysis with more variability and some Maillard complexity. Pit-roasting (80–120°C alternating, 72–168 hours) is the least efficient in yield terms but produces the greatest phenolic smoke character from wood combustion products absorbed into the piña during slow cooking.

The Tahona and Fibre Fermentation

In artisanal and ancestral mezcal production, cooked piñas are crushed using a tahona — a large volcanic stone wheel (typically 1–2 tonnes) rolled in a circular pit (canoa) by mule, horse, or tractor. Unlike mechanical roller mills or diffusers that separate juice from fibre, tahona crushing produces a slurry of juice and fibre that ferments together. Fermentation with fibre significantly affects the final spirit: the agave fibre (cellulose, hemicellulose, residual fructans) provides additional substrate for microorganisms, increases surface area for wild yeast and bacterial colonisation, and contributes woody, fibrous, and earthy flavour compounds. The resulting tepache (fermented agave slurry) is distinctly more complex in congener profile than a clean-juice ferment.

Wild Fermentation in Artisanal Mezcal

NOM-070 Artesanal and Ancestral categories permit (and traditional practice mandates) wild-yeast fermentation. The agave growing environment, the roasting pit, and the fermenting vessel surfaces host complex communities of Saccharomyces, Torulaspora, Kluyveromyces, Metschnikowia, Candida, Pichia, and various lactic acid bacteria. This microbiome diversity produces higher levels of esters, higher alcohols, and organic acids than a controlled Saccharomyces-only fermentation — contributing to artisanal mezcal's extraordinary flavour complexity. López et al. (2020, Foods 9(1):95) characterised the mezcal fermentation microbiome across multiple Oaxacan producers, finding significant batch-to-batch and producer-to-producer variation in both yeast community composition and resulting congener profiles.

The Mezcal–Tequila Distillation Comparison