You’ve hopefully already read the first post in this series concerning how agave is harvested. This part will cover the cooking of the piña, mashing, fermentation and distillation.

Cooking

After harvesting, the agave hearts (piñas) are transported from the field to the distillery. Most distilleries have facilities to process the piña all the way from plant to spirit, but some of the smaller producers are known to buy in processed agave syrup ready for fermenting.

Off the truck the piñas are cut up ready for loading in to ovens. All but the smallest piña are chopped in half (or quarters if they are particularly big), this usually takes place on patios in front of the ovens. The hearts are then carefully loaded into giant steam ovens ready for baking. We actually got near an oven in operation and the smell was reminiscent of pungent tequila aroma itself.

Before the 19th century agave hearts were roasted using wood fueled fires in much the same way that Mescal is still produced today. But Jaliscos forests were significantly depleted by the turn of the 18th century due to the demand for wood to heat the ovens so Tequila producers switched to steam ovens. Still fueled by wood, but far more efficiently, this changeover meant that less fuel was required and that more of the natural qualities of the agave were retained over roast character (which is noticeable in Mescal).

The process of baking the hearts is an important part of production as it converts the natural starch within the vegetable into fermentable sugars. The temperature of the oven is relatively cool so as not to burn the outside of the piña and leave the inside uncooked, usually around 170°C (but this figure varies). Other producers may choose to cook faster and hotter.

Some producers, Don Julio being one of them, choose to use a two stage cooking process. An initial two hour cycle that caramelises many of the external waxy compounds and then a full 72 hours to cook the piñas all the way through. After the initial two hour burst the liquid at the bottom of the oven, which sits in troughs, is drained away as it contains bitter grassy flavours.

Mashing

After cooking the piñas are now soft and sweet, I ate some and it reminded me of a very sweet sweet potato. The sugar content of a roasted piña should sit at around 20% (20 Brix). Jose Cuervo for one, test five piñas from every truck load that arrives for potential sugar before roasting, they aim for 20-25 Brix and if the quality of the samples is low enough they’ll reject the whole truck (and the Jimadores don’t get paid).

The piñas are sent for crushing where they are first mixed with water. The mashing can work in various different ways, it was originally done with wooden mallets! At Don Julio the mash moves along a set of conveyor belts where it is repeatedly mashed and pressed. At each stage the juice is extracted, a total of five times, with varying degrees of clarity and purity at each stage. These sweet juices are then collected together ready for fermentation.

More water is added until a level of around 15 Brix is achieved, any higher than this and they yeast would not be able to survive. The aquamiel (honey water) is then transferred into fermentation vats where the yeast culture is introduced.

Fermenting

As we know fermentation is a very complex subject, so to keep this short i’ll stick to some basic facts. The final alcohol alcohol after fermentation will be around 5% ABV. This stuff is called mosto (must, or wort) and the process can take only a few days or up to two weeks depending on the the style of product that the distiller is aiming to produce. This length of time depends on the strain of yeast, temperature of fermentation (20-26°C for a quick fermentation). Ultimately the yeast will die once the alcohol reaches 5-6%, but once again this depends on how resilient the particular strain is.

The most important thing is to prevent the fermentation vat from getting too hot during the midday sun, if the liquid temperature rises above 30°C it could kill off the yeast, which would be disastrous. This can be prevented to a certain extent by using very large fermentation vessels that take a long time to adjust to ambient temperature. There are 20 vessels at Don Julio’ LA Primavera distillery and each one is around 20,000 litres in capacity, at Jose Cuerveo’s La Rojena the vats are over twice the size.

Don Julio actually use a strain of yeast that has been cultivated from the natural yeasts that ferment agave leaves. The brand Herradura claim to be the only producer that use natural airborne yeasts, leaving fermentation entirely to chance. Although this is certainly an interesting facet to their production process it could and can result in a inconsistent product.

It it also worth mentioning that it is at this stage that Jose Cuervo introduce additional non-agave sugars to their product when making mixto Tequilas. Molasses, corn or any other non-agave sugar source can account for up to 49% of the sugar that makes up a mixto tequila, the other 51% (at least) being from the blue agave. I found this interesting as I wasn’t previously aware that the two different products were fermented together, which actually added a certain level of credibility towards mixtos for me personally.

Distillation

Nearly all Tequilas are distilled twice. A double distillation is the legal minimum, as stipulated by the Tequila Regulatory Council, but there are some producers who choose to distill three times, or use a continuous still. Both the use of the  continuous still, or distilling a third time have the effect of purifying the spirit, making it much more susceptible to age characteristic and generally lighter in character. This is quite rare however, because the very best brands of Tequila are renowned for capturing the agave essence in their product.

Don Julio use sixteen different stills, all of them are different combinations of copper and stainless-steel and therefore each produce a slightly different distillate. Ultimately the distillates of all but still number 16 are blended together to make Don Julio Blanco, Reposado and Anejo. The smaller number 16 still is used only to produce the 1942 and Real varieties of Don Julio, which lead the way at the very pinnacle of Tequila quality (at a price!). It’s worth mentioning that copper does have a distinct effect on the liquid over SS in that it erodes into the liquor over time, imparting a very subtle character that is measurable in some finished Tequila.

Jose Cuervo use entirely copper stills (picutred) for production of Classico, Especial, Tradicional, Platino and Reserva de La Familia.

The first distillation produced a liquid of around 25% known as Ordinario.  When distilling for the second time the liquid will condense through over a length of hours. As time goes by the run of liquid changes from very light alcohol with low boiling points (such as methanol), right up to heavy alcohols that boil at much higher degrees (collectively known as fusel oils). Both ends of the distillate contain undesirable chemicals and it is the job of the distiller to ‘cut’ the heads and tails, both for the safety of the consumer, but also as a means of refining their product down to the desired flavour/aroma.

Every litre of the 100% agave clear heart that is run off the still will have required nearly 9kg of agave piñas to make it at 55% ABV.

Tune in next time for the final part in the series where we examine aging, bottling and styles.

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