Physical, Chemical, and Microbiological Characteristics of Pulque: Management of a Fermented Beverage in Michoacán, Mexico

Abstract

Pulque is a beverage that has been prepared in Mexico since pre-Hispanic times from the fermented sap of more than 30 species of wild and domesticated agaves. We conducted studies in two communities of the state of Michoacán, in central-western Mexico, where we documented its traditional preparation and analyzed the relationship between preparation conditions and the composition and dynamics of microbiological communities, as well as the physical and chemical characteristics of the beverage. In one of the communities, Santiago Undameo (SU), people boil the sap before inoculating it with pulque inoculum; this action causes this local pulque to be sweeter, less acidic, and poorer in bacteria and yeast diversity than in the other community, Tarimbaro (T), where the agave sap is not boiled and where the pulque has more diversity of microorganisms than in SU. Fermentation management, particularly boiling of the agave sap, influences the dynamics and diversity of microbial communities in the beverage.

Keywords: agave sap; biocultural diversity; probiotics; traditional knowledge.

Figure 1

Studied localities in the state of Michoacán. Tarímbaro (T, square) to the north, and Santiago Undameo (SU, circle) to the southwest of the city of Morelia.

Figure 2

(A) Extraction of fresh sap “aguamiel” in SU in the species A. salmiana var. salmiana. (B) Inoculum for the pulque, “foot of pulque”, in a plastic barrel in T. (C) Boiled sap in SU.

Figure 3

(A) Abundance of lactic acid bacteria (LAB). (B) Abundance of yeasts. (*) was a different treatment to the rest according to multiple Tukey tests (p < 0.05). (C) Diversity (Shannon–Wiener Index H´). Different letters in rows indicate significant differences according to Tukey tests (p < 0.05). Phases: fresh sap (FS), boiled sap (BS), pulque (P) and inoculum for pulque (IP). Sites: Santiago Undameo (SU), grey bars, and Tarímbaro (T), white bars.