During the fermentation process the sugars in the agave juices are transformed into alcohol. In the past, fermentation took place in large wooden vats, while today it takes place in stainless steel tanks. This step separates high-end 100% Weber Blue Agave tequilas from the "mixtos".
Once aguamiel, water and natural yeasts are combined in the fermentation vats, the yeasts start to grow, consuming the sugars and changing them into alcohol. The fermenting liquid is called “el mosto”. Each craft distillery has its own yeast culture that they have developed over the years. The type of yeast used in fermentation has a tremendous effect on the taste of the finished product. That is why each distillery keeps their strain of yeast a closely guarded secret.
Depending on the atmospheric temperature, fermentation can take from 6 to 12 days. The tanks get warm from the chemical reactions, and the mosto can bubble quite violently. Once the fermentation is complete, a bubbling liquid turns still; it tastes like warm beer and has an alcohol content of 5 to 8% percent. Mosto is allowed to rest for several hours before it is piped into the alembics or stills.
To speed up this process, many distilleries use commercial strains of yeast and add chemical accelerants (such as ammonium nitrate and urea), which shorten fermentation time to mere several hours. However, the spirit’s taste depends largely on the length of fermentation and rushing this process prevents tequila from acquiring complex, rich flavors.
To preserve authenticity of Arrogante tequilas, we use two strains of natural yeast in the fermentation process and never add any chemical catalysts and contaminants. The process generally takes 10 days but the resulting taste and aromas are rich and complex because tequila develops its flavor profile during fermentation.