How Mezcal is made
Traditionally, wild agave was used to make mezcal (also known as maguey), and while this is still the case, demand and commercialisation have led to mostly cultivated agave being used. It's crucial that only agave that have reached maturity are used and different varieties of agave reach maturity at different times, anything from six to 35 years.
When the agave reaches maturity, the leaves are cut off with a machete or coa, a heavy semi-rounded blade on a long rod. A coa or an axe, is used to cut the roots to leave the core/head of the plant, called a piña. The piña are transported to a palenque (mezcal distillery).
The equipment in each palenque varies considerably, as does the process used by each mezcalero (mezcal distiller). The differences in equipment and process greatly affect the flavour of the finished mezcal and also determine the mezcal category the finished product can be labelled as.
Cooking
Espadín piña, the most commonly used agave variety in mezcal production spherical, weighing 30 to 50 kilos, and are cut into two halves, or quartered if large, and thrown into an oven (horno). This traditionally consists of a large hole dug in the ground, lined with volcanic rocks. These are preheated by burning wood.
When the mezcalero decides the desired temperature has been reached, stones and a layer of agave fibres (bagazo) from the last crushing are spread over the fire. The raw piña carefully placed over the bagazo with the largest pieces nearest to the heat source and the smallest at the top. The hole is covered with earth to form a dome-like crust over this piña pie, which is left to slowly roast for three to five days.
A prepared pit ready to be lit at San Baltazar Chichicapam.
The construction, preheating and layering of this pit – oven is an art and each mezcalero has their own beliefs for what works best. Some make a hole in the top of the mound that caps the pit, in which they poor water to steam cook the agave. It's common to see the mound topped by a small cross to ward off evil spirits.
Mound atop a pit at Santa Catarina Minas.
Some mezcalero use masonry ovens instead of pits. Both pit and masonry ovens slowly roast the piñas, caramelising them and, in the case of pit ovens, imparting a delicate smoky note.
The brick oven at Lost Explorer's palenque in San Antonio, Oaxaca.
More industrial mezcal distilleries use stainless-steel autoclaves, which roast the piña in days rather than weeks. These can be run very efficiently or at lower temperatures for longer. However, autoclaves don't tend to impart the same flavours as the slow traditional roast.
A few very industrialised distilleries use what is called a diffusion process rather than roasting agave. This process involves crushing raw agave and then striping the plant 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 contentious method saves on manual handling of agave, is more efficient at extracting sugars and considerably reduces the production time. However, this method produces mezcal lacking the complex flavours that result from slow oven roasting, and many argue that the spirit produced should not be permitted to be called mezcal.
Crushing/Milling/Grinding
The roasted piña is then crushed to separate the sugary juice from the fibre.
Very small distilleries load the brown roasted piña into a trough, hollowed tree trunk or rectangular hole formed in concrete. The piña is then pounded with a wooden club that resembles a tool from the Flintstones. Larger distilleries use a stone wheel called a 'Tahona' pulled around a circular stone pit by a pony or small tractor. Larger distilleries use a roller mill or other mechanical shredding machine (molino).
A Tahona at Santa Maria Albarradas.
Most experts consider there to be little discernible difference in the finished mezcal when mechanical shredding machines are used compared to traditional labour-intensive methods.
Fermentation
The sugary juice and often also the fibres (bagasse) from the crushed piña are transferred to fermentation vats (traditionally wooden) called tinas, clay pots or even animal skins. Modern masonry tanks and stainless steel vats are also used.
Traditionally, wild airborne yeasts start fermentation, but larger distilleries tend to use cultivated yeast to ensure continuity and quality. While the fermentation vessel and whether fibres are used influences the category a mezcal falls into, the use of cultivated yeast doesn't. Even ancestral mezcal can be made using cultivated yeast.
Tinas at Santa Maria Albarradas.
Depending on the type of vessel, its size, the yeast used, and how warm the weather is, fermentation lasts several days to several weeks and produces a lightly alcoholic mosto.
Distillation
Traditionally, the mosto is then distilled in pot stills, which are usually made of copper, but some are still made of clay with bamboo tubing. (Industrial distilleries also use column distillation, but such mezcal cannot be labelled artisanal or ancestral.)
The first distillation produces ordinario, a weak alcohol around 20% alc./vol.. To make mezcal, the distiller must redistil this ordinario a second time. Hence, mezcal is said to be "double distilled."
During both distillations, volatile alcohols, the heads or puntas run from the still first. Then follows the heart el corazón, the desirable spirit starts to flow. This is collected until the distiller judges the need to cut as the tails, or colas, which contain methanol and undesirable oils, start to flow.
Some, or all, of the heads and tails may be redistilled with the heart in the second distillation. Where the distiller makes the cut from heads to heart and heart to tails during the second distillation is crucial to the quality of the finished mezcal.
Copper pot still at Santa Maria Albarradas.
