Tinacal

The tinacal is the fermentation room (and, by extension, the wooden or stone vats inside it) at a pulque hacienda. Aguamiel drawn by the tlachiquero with an acocote is brought into the tinacal and emptied into open-topped vats, where wild yeasts (principally Saccharomyces cerevisiae, but also Pichia, Candida, and other minority genera) and bacteria (notably Zymomonas mobilis and Leuconostoc mesenteroides) convert the sweet sap into pulque within hours. A small portion of the previous day's pulque, called the semilla ("seed"), is added to each new vat to inoculate it. The fermentation is fast, alive, and never finished: the drink is still fermenting when it leaves the tinacal for the pulquería.

The tinacal's microbial community is the cumulative product of decades or centuries of continuous use. Wooden walls, ceiling beams, vat staves, and the floor itself harbor the resident yeasts and bacteria that define a given hacienda's house style, in the same way a sourdough kitchen's microbiome is its working asset. A tinacal that has been thoroughly scrubbed loses its character for weeks or months until the community re-establishes; old pulqueros treat the room with the same protective discipline a cheesemaker would treat an aging cave. The drink that emerges is documented in the history chapter's pulque sections, and the fermentation microbiology, including the Zymomonas contribution that distinguishes pulque from any other fermented sugar, is walked in the distillation chapter's microbiology subsection.