How is tequila made
Tequila is a distilled spirit made from the cooked and fermented juice of the agave (pronounced ‘Uh-Gah-Vee’), a spiky Mexican plant which resembles a cactus. Traditionally the process is labour intensive and artisanal – and many tequila distilleries still operate this way. However, like in most industries, technology has both speeded up the tequila making process and made it less labour intensive
Even in the most technologically advanced facilities the process remains something of an art, starting with the labour-intensive hand-cutting and harvesting of agave, a plant that takes five to 12 years to reach maturity.
1. The agave plant
Tequila is made from the agave, pronounced 'Uh-Gah-Vee'. A native plant to Mexico, its name originates from a Greek word meaning 'noble' or 'admirable'. In Mexico the plant is also sometimes referred to as 'Maguey' (pronounced 'mag-gay').
Despite its spiky appearance the agave is not a cactus but a succulent plant with a botanical classification closely related to the sansevieria, yucca and amaryllis, part of the Century plant family and the genus Agavaceae. The simple and commonly accepted definition is that the agave plant is a member of the lily family.
There are 166 different species of agave, 125 of which are found in Mexico. These grow in a wide variety of sizes and colours but since 1964, legally only one, Agave Tequilana Weber Azul, can be used to make tequila. Named by a European botanist named Weber the plant is better known simply as 'Blue Agave' due to the slight blue hue to its green foliage, very evident when viewing an entire agave field in Jalisco. Other Mexican spirits such as mezcal and sotol are chiefly produced from other varieties of agave.
The Blue Agave reaches 1.2 to 1.8 metres (4 to 6 feet) high and is basically a vast, spherical ball, studded with serrated bluish green, silvery, spiked leaves (Pencas), which jut out 90cm to 120cm (up to 3.3 feet) and end in a sharp brown thorn, giving mature plants a diameter of 2.1 to 3.6 metres (7 to 12 feet). The plant flourishes in the silicate-rich, volcanic soil in Jalisco and the surrounding Mexican states.
Agave are planted immediately before the rainy season (June to September) so that the plants do not suffer from water stress during their first year of growth as the agave absorbs enough water during this period to allow healthy growth throughout the year without irrigation. January to May is the best season to harvest agave as this is when the plant generates its highest yield. Due to muddy fields and other associated difficulties with harvesting during the rainy season many distilleries close for holidays and maintenance.
A hijuelo growing from an agave
The agave is asexual and has various means of reproduction (apart from human biotech) - by flowers pollinated by a specific species of bat (Leptonycteris nivalis) bearing seeds and offshoots (hijuelos), which grow in the soil around the plant from its rhizomes (ground roots) and also form on the flower stalk (quiote).
Seeds are rarely used for commercial cultivation. The hijuelos start to form after the plants second year but are often not removed to propagate new plants until the third to fifth year depending on a farmer's personal preferences. The size of hijuelos is measured by agave farmers in terms of "lime, orange and grapefruit sized children". These are planted by hand in straight rows typically one to two meters between plants and three meters between rows with 2,000 to 4,000 plants per hector (2.5 acres). Some larger producers now also use micro propagation (reproducing baby plants using adult plant tissue).
Cut hijuelos ready for planting
To comply with the rules of the Mexican Official Standard all agave grown for tequila production must be registered with the Tequila Regulatory Council (CRT). There are over 22,000 registered agave farmers cultivating some 400 million agave, planted over 125,000 hectors (308,875 acres) of land, which is around 3% of the total available land within the DOC Tequila region.
Like all crops the agave requires tending. Weeding is necessary twice a year and the plants are sporadically checked for infestation and fungal diseases. Some farmers cut off the tips of the agave's leaves with a machete. Known as chaponeo o barbeo this practice reduces the risk of infestation by an insect called picudo in the hollows that form at the ends of the leaves. It also allows the agave to be planted closer together. Cattle and fire can seriously damage plants and once every 100 years - so can snow. In 2005, snow killed thousands of young plants and seriously damaged more established older crops.
flower stalk (quiote) rising from an agave
In April, as the female plant nears maturity a tall flower stalk or quiote (pronounced 'Kwai-O-Tee') sprouts from the centre top of the plant. This can grow up to 6 metres (20 feet) tall and if left to develop renders the agave useless for tequila production as the plant's energy reserves (in the form of inulin) are used to grow the quiote. Hence, the quiote is cut off so forcing the sap to be diverted to the heart of the plant, or piña. The sprouting of the quiote marks the end of the agaves lifecycle, after which the plant will die.
2. Harvesting agave
Agave usually reach maturity after five to eight years when the piña swells and ripens ready for harvesting. Plants grown in the highlands take longer to reach maturity (up to 12 years) than those grown in plains or valleys and its common practice to fertilize agave to speed maturity and increase yields. Without the correct management, even valley grown agaves can take 12-15 years to mature.
There is no minimum statutory age before agave can be harvested and plants are hand selected for harvesting according to their maturity, though entire fields are usually harvested at a time. The adult agave reaches some 1.8 meters (6 feet) tall but mature plants are shorter due to their leaves spreading outwards and dropping rather than growing vertically. Another sign of maturity is the loss of the plants lowest leaves (pencas).
The biomass of Blue Agave is approx. 50% leaves and 50% piña roughly comprising 70% water, 5% fibre and 25% carbohydrates (inulin). Ripe piña from mature agave plants have more sugars so give a higher yield and produce superior tequila. The ART (total reductive sugars) of agave considered ripe for harvest are measured, usually by using optic refractometer to measure BRIX and then subtracting 20% to determine the ARTs. The average industry sugar content for tequila production is around 21% but some agave can be as much as 45 BRIX.
Ripe piñas have an average weight of 32 kilograms but vary from 10kg up to 100kg (22 to 220lb), although 180kg (400lb) specimens have grown. The concentration of sugar is usually 22-28% (mostly Inulin) a juice content of 0.572 ml/g and a pH of 5.2. It takes around seven kilograms (15.5lb) of piña to make a litre bottle of 100% agave tequila.
The harvesters, called jimadors, use a long-handled knife called a coa to remove the long, spiky blue/green thorn-ended, barb-edged leaves to expose the piña, which looks rather like a huge pineapple. The tool is named after the 'hee' sound made as the coa moves through the air.
Red patches on ripe piña
When the agave reach perfect maturity - reddy-brown spots of bleeding sap are apparent on the surface of the piña after the pencas have been trimmed off. Four to six such spots on one agave indicate peak maturity, seven or more is a warning that the piña is starting to decompose. This is comparable to the way brown spots on a banana skin are indicative of ripeness. When the agave rich peak ripeness for harvesting the tequileros only have six months to a year to harvest the plant or it will start to decay.
Some distillers favour overripe agave while others prefer underripe agave - the degree of ripeness influences the character of the tequila produced from it. Underripe agave tend to produce less complex tequilas with vegetal notes while overripe agave usually result in rounder, sweeter, full-flavoured tequilas. Agave past peak ripeness, called sobre maduro (overripe) start to produce acids which impart extra flavour and complexity to tequila but also often with a vinegar-like note.
Jimadors work from sunrise to shortly after midday to avoid the worst of the scorching afternoon heat and a skilled worker is expected to harvest over 100 piñas of agave a day. This is a highly skilled profession and the techniques tend to be passed from father to son. Even experienced jimadors have been known to lose toes to the coa's blade. Tarantulas and snakes attracted to the shady spots under the plants are also hazardous.
Premium tequila brands often carry claims that the agave used in their production are "estate grown". This means they are grown on land owned or leased by the distillery so allowing the distiller to control the way the plants are tended. Using their own jimadors to harvest also ensures the leaves are cut right back close to the piña. When third-party growers sell their piñas to distilleries they are paid according to weight so, unless the distillery has strict standards, tend not to cut the leaves back as closely, so earning more for their crop. The disadvantage to this is that the leaves waxy surface is bitter so adversely affects the flavour of the finished tequila. Better producers who use third-party growers have contracts covering the 6 to 12-year life cycle of the piña so they can ensure quality and continuity.
When harvesting a field, a good jimador will also leave plants which he considers not to have reached sufficient maturity or are over mature. These abandoned plants can be seen dotting the leaf-strewn ground of newly harvested fields.
3. Cooking the agave
Depending on their size, the harvested piñas tend to be cut into in halves or quarters to facilitate uniform cooking.
Loading a traditional horno oven with split piñas
The pieces are manually fed into the ovens often with the aid of conveyors, where they are stacked by hand. Here they are steam-baked to convert the starchy sap contained in the piña into fermentable sugar. (Raw agave tastes like dried potato.)
Traditional horno oven. The floor is designed to allow juices from the piñas during cooking to run from the oven for collection.
Traditionally a steam heated masonry oven called a horno is used to slow bake the agave for 24-48 hours. The steam is then shut off and the baked piñas left to cool for a further 16-48 hours to complete the cooking process. Each distillery will operate their ovens at different temperatures, for the period they think works best, with cooling sometimes speeded up by opening the oven door and/or by the use of fans at the top of the ovens.
Autoclave ovens being unloaded after cooking
Many distilleries now use modern autoclaves in place of the traditional hornos. These are basically huge stainless-steel tubes with a sealable door at one end and act like giant pressure cookers to bake the agave within a fraction of the time (around 7 hours at a pressure of 1.2 kg/cm2 and a temperature of 121°C.). Due the steel sides dissipating heat more quickly than masonry, the cooling period is also reduced. Cooking too quickly increases the risk of burning the sugars and creating a bitter caramel taste. Slow baking results in more fruit and sweetness.
Unloading roasted piñas from traditional hornos oven
The agave plant stores its energy as inulin, a long chain fructose molecule. During the cooking process steam softens the piñas texture and hydrolyzes the inulin into fructose. The sugar can then be fermented into alcohol. Thus, both hornos and autoclaves convert inulin into fermentable sugar by temperature. Although not traditionally used in tequila production, this conversion can also be achieved using acids or special enzymes (active proteins).
Roasted piñas after cooking
Mule pulled Tahona wheel crushing piña
After cooking, the piña must be shredded to release its sugary juice. Traditionally, the baked piñas are crushed using an ancient kind of mill called a Tahona.
Machine pulled Tahona wheel crushing piña
The Tahona stone is driven around a circular pit (originally pulled by mules or oxen) while the baked piñas are manually moved into the path of the rotating wheel which squeezes out the sugary sap. Today, only six tequila producers we know of still use tradition Tahona mills to crush piña:
- El Pandillo (not strictly a Tahona, but Filipe Camarena's Frankenstein, a 19,000 pound steel roller, works in a similar way.
Roller-mill shredding and washing sugars from agave fibers
Only seven tequila producers still use Tahonas and most producers now employ modern roller-mills which use conveyor belts to move the cooked piñas through a series of crushers while water is sprayed over the exposed fibres to literally wash the sticky sugary juice (aguamiel) from the fibres. The last set of rollers squeeze the fibres dry using a mangle-like action to remove as much juice as possible. The watery juice passes through a pachaquil which screens out larger particles. The size of particles allowed through to the fermentation and distillation processes also has an influence on the tequila's final flavour.
Contentiously, some producers, most notably Sauza, no longer cook the agave in hornos or autoclaves but use what is called a diffusion process. This crushes the still raw agave and strips the fibres using steam in a diffusor. Sulphuric acid is added to lower the pH and the juice is heated for a couple of hours at 95°C to hydrolyze the inulin. This relatively new method saves on manual handling of agave, is more efficient at extracting sugars and considerably reduces the production time. However, traditionalists like me believe this method produces tequila which lacks the complex flavours that result from oven cooking.
The fermentable sugars in the aguamiel (agave juice) can now be converted into alcohol using yeast. Prior to fermentation the aguamiel will be analyzed to measure the levels of fermentable sugars and the aguamiel may be diluted with water to reduce the concentration of sugars to a level (8-16%), depending on sugar tolerance of the yeast strain. Mosto (wort) formulation is usually based on experience rather than the application of science.
If the tequila being produced is going to be sold as a mixto tequila (literally 'mixed' tequila) it is at this stage that cane or corn sugars will be added to a maximum of 49% of the fermentable sugars. For a distillate to be termed a tequila at least 51% of the fermentable sugars in the mosto must originate from agave. In 100% agave tequila, only blue agave aguamiel is fermented with no added sugars.
The type of yeast (or yeasts) used and any nutrients added during fermentation will determine the flavour and characteristics of the finished tequila. Traditionally, spontaneous fermentation using naturally occurring airborne yeasts would be relied upon. Casa Herradura, La Alteña and Siete Leguas most notably still use this method, but most other distillers use commercially produced yeasts or their own proprietary strains. Fermented juice from a previous batch is generally mixed into new fermentations to ensure continuity.
Open wooden fermentation tanks
Fermentation can be in open or closed vats of wood or stainless steel construction and typically lasts 24-96 hours depending on the type of process to produce a beer-like mosto (wash) of 3.8 to 6% alc./vol..
The fermentation vats are often aerated at the start of fermentation to encourage aerobic fermentation causing the yeast cells to multiply. Later in the process, the air supply bubbling through the vat is stopped to start anaerobic fermentation, so encouraging the yeast to produce alcohol. Larger distillers usually have cooling systems on their stainless-steel fermentation vats to keep the temperature below 40°C as higher temperatures will cause the fermentation to stop.
Open wooden fermentation tanks with agave fibers
Those distillers still using traditional Tahona mills to crush the piña usually ferment the aguamiel with some of the agave fibres from which it was extracted. The agave fibres, which float, form a seal so helping trap aromatics in the fermentation. It is also usual for the agave fibres to be collected from the fermentation tank and put in the distillation still with the mosto.
Stainless steel pot stills
To make tequila the mosto must be distilled at least twice and this may be by a combination of pot and column stills or traditionally, be entirely using pot stills. The stills may be copper or stainless-steel but it is essential to have some copper contact during distillation so even stainless-steel stills have some copper and this is most usually by use of copper serpentine steam elements in the base of the kettle or copper tubing in the condenser.
The product of the first distillation is known as ordinario and it is only after a second distillation that the distillate may be termed tequila. Although very rare, some distillers distil their products a third time. First distillation called destrozamiento produces a spirit of around 20-25% alc./vol.. The second distillation (rectification) typically produces a distillate of around 55-75% alc./vol.. Better distillers aim nearer to 55% rather than higher strengths to better preserve agave flavours in the distillate.
Traditional copper pot stills
The distiller exercises considerable control over the style of tequila produced and a combination of art and science will dictate when to 'make the cut'. Different flavouring compounds evaporate at different temperatures, and the distiller has to find the right balance. He (sadly it is almost always a he) will select only the 'middle cut' of the spirit flow to be set aside as tequila. The first spirit to flow from the still, known as heads and the last, known as tails, are usually returned for re-distillation with the next batch of mosto or the start of the next second distillation. (Please see science of distillation for detailed information on cuts and distillation in general.)
Traditional copper pot stills
Incredibly there is no regulation governing the maximum strength a tequila may be distilled to so using column stills it would technically be possible to produce a practically neutral tasting tequila. Agave vodka anyone?
Cask aging tequila
7. Maturation (optional)
The clear tequila that results from second distillation may be bottled and sold as 'blanco' tequila. In contrast, reposado and añejo tequilas must be aged in oak, so over time the wood can impart tannins that soften and mellow the spirit and add character. (Note, blanco tequilas may rested in/on oak for up to 60 days.)
Unlike more categories of spirit, there is no regulation controlling the maximum fill strength of tequila going into a cask.
The casks used may be new or previously used to age tequila or another spirit, most commonly American whiskey. Casks may be toasted or charred to add colour and flavour. (Acids in the layer charcoal toast lining the inside of the cask react with alcohol to produce esters.)
Pipone aging vat
The type of wood, thickness of stave, level of toast, previous fill, number of cycles in the cask, temperature, humidity and entry alcohol level all combine to dramatically affect how tequila matures. Reposado tequilas may also be matured in vats called 'pipones'.
CRT seal to prevent tampering with aging tequila
Whether cask or pipone, the regulations dictate that the container in which ageing takes place must remain sealed throughout the duration with paper seals put in place and removed by the Compliance Assessment Agency.
8. Blending & additives
Additives such as caramel colouring, glycerine, sugar syrup, older tequila, oak (natural or Encino) extract, aromatizers and flavourings (permitted by the Mexican Ministry of Health) may also to added to all aged categories of tequila - up to 75 grams per litre of sugar and 85 grams per litre of other additives, but (total dry matter) must be less than one percent of total volume. Although some may question its enforcement, a rule change introduced in February 2013 prohibits the use of such additives in blanco tequila.
9. Filter & dilute
It is commonly believed that a tequila must have a minimum alcohol content of 38% alc./vol. but the rules actually allow a tequila to be bottled at a strength between 35% and 55% alc./vol.. Distilled or demineralised water is used to dilute to bottling strength. Prior to bottling the tequila may also be filtered through mediums such as charcoal or cellulose, at ambient temperature or by chill-filtration.
10. Bottling & Packaging
Mixto tequila for distribution outside of Mexico is often sold in 'bulk' and exported in tanks or tankers at a high alcohol strength to be diluted and bottled in the country where it is to be sold or re-exported from. In contrast, '100% agave' tequilas must, by law, be bottled within the denominated tequila region.
While the Mexican regulations permit tequila to be bottled at between 35% and 55% alc./vol., local regulations in export markets are often more restrictive. In Mexico tequila is usually sold at 35% to 38% alc./vol., the U.S. market stipulates a minimum of 40% alc./vol. while South Africa is 43% alc./vol. and Europe 37.5% alc./vol.. Thus, it is common to see a brand at 35% alc./vol. in Mexico, 40% in the U.S. and 38% in Europe. Personally, when I see so called "super-premium" brands at 40% in the U.S. and at a duty saving 38% in Europe, I question the validity of their "premium" status.