Perhaps the most vilified thing in the world of mezcal, the diffusor is a massive piece of industrial equipment that uses hot water and mechanical shredders to extract the carbohydrates from agave, sugar cane, wood, or fruit to produce a distillate. They are predominantly used to produce tequila at large volumes.
Distillation is actually the final step in a process of converting sugars into alcohol. Spirits made from fruit can jump immediately to fermentation because the sugar content in the fruit is high enough for yeasts to get things going immediately. But agave and grains are all starch so they have to undergo another step, first distillers have to transform those starches into sugars using heat directly in underground pits or indirectly in ovens. Distillers crush the roasted agaves to make a rich mash of sugars, fibers, and other native yeast and bacteria which are fermented into a slurry that provides the foundation of an agave spirit’s flavor.
Diffusors are machines that speed up that process and make it much more economical. Essentially they are a hot water shower that breaks down agave into a slurry that collects much more of their distillable matter in an extremely efficient manner. Some claim that efficiency can rise to 99% of agave sugars. There is also the potential to use sulphuric acid after the hot water/mechanical shredding step. Some distillers definitely used this chemical in the past but it is unclear whether this is still used today.
They can be used in two ways: They can pull sugar from previously roasted agave or pull starch from raw agave and then cook the resulting material. If agave was previously roasted and crushed then the resulting bagasse is washed with hot water to extract as many of the sugars as possible. Distillers can also feed shredded raw agave into a diffusor. In that case the water pulls starch from the agave which is then cooked in an autoclave. The liquid from both processes is then fermented and distilled. Khrys Maxwell has a wonderful blog post about diffusors that describes how they work in much more detail while also digging into who was using them around 2012.
Perhaps the most important factor about diffusors is that they don’t care about the ripeness of agave. They transform any type of agave starch into fermentable sugars. That means that producers don’t have to wait for agaves to become fully ripe. Since the Blue Weber agave used in tequilas takes about six years to fully mature, any reduction in that maturity means more money for growers and producers. When diffusors can make the same, at least very similar, spirit from four year old agave, that’s a 50% reduction in time which represents a massive savings.
Since this is an industrial process, it also can produce a highly consistent spirit. The aim for many diffusor produced agave spirits seems to be exactly that: If they can deliver a product to bars that will fit neatly into cocktail recipes and guarantee that bartenders and drinkers are getting as close to a perfectly consistent product as possible, then they’ll be fulfilling the market’s desires. Of course, this is the antitheses of traditional agave spirits which vary batch by batch depending on a bewildering menu of factors ranging from agave type and ripeness to the weather during fermentation. Traditional agave spirits producers have aimed to highlight these variations because they are the expression of the process and highlight the realm of possibility in these spirits.
The major issue with diffusors is that they tend to remove flavor from agave spirits. Traditional agave spirits get their flavor from each step in the distilling process: They undergo slow roasts, mechanical crushes, slow natural fermentations, and distillations – each step contributes nuance and balance to the final spirit. Distillers can speed up most of these steps just by using a diffusor at the cost of all the rich flavors produced by slow traditional processes. But many of these agave spirits do have rich flavors. Generally that’s because they use additives which contribute texture and flavor to what would have otherwise been rather insipid spirits. This process has become so wide spread that there is now a counter certification program for additive free tequilas. This is perfectly legal for tequilas and mezcals in the top level “mezcal” class under the NOM 70 designation.
While once common among large volume industrial producers, diffusors seem to have really taken over in the tequila industry when the price of agave steadied and rose starting about 2015. Previously agave prices oscillated wildly over cycles: As demand increased more people planted agave but in the six or so years that it took them to ripen it became clear that so many people had planted agave at the peak of the market that there was a glut of ripe agave at the end of those six years. Prices would go from 16 pesos a kilo to half a peso a kilo years later. That boom and bust cycle seemed to be self sustaining until demand took off like a hockey stick. Agave prices rose along with demand and everyone was searching for a solution – voila! the diffusor can transform underripe agave into agave spirits that you can sell today. Things have changed so much, so rapidly, that Maxwell told me his original list of diffusor distillers “probably doesn’t matter anymore” because so many brands are now using them. That’s the only way they can make a tequila at such a low price for the cocktail market.
Diffusors were once viewed as the existential threat to mezcal. Today, it seems that only a few brands like Zignum use them. This may be because of the cost but also because the rest of the industry has adapted to demand with other approaches. Larger production brands blend many batches of ordinario or build out parallel production lines. Each single line looks like a palenque but they can adapt to demand by building more and more as long as they have the space. That has been cheaper than huge industrial investments and, while definitely changing local culture, has the benefit of keeping more economic benefits from the mezcal boom local. It can be very difficult to figure out how some larger production mezcals are produced and, given recent reporting from Mexico about lower than reported ABVs in some mezcals there is lots of debate about what caused this.
As for the future, it’s anyone’s guess. There’s an argument that the combination of economic, developmental, and regulatory factors both prevent huge industrial investments in equipment like diffusors while simultaneously incentivizing producers to retain elements of traditional production. The tequila brands that are successfully focused on traditional production certainly seem to have carved out a niche for themselves and that may provide an even stronger role model. But, as with all things in the mezcal world, the chaos of regulation is dark cloud which obscures and clear vision of the future.