Pozol

A maize dough that becomes a drink

Pozol is a fermented maize dough and the drink made from it. Maize is cooked with lime, ground, shaped into balls and wrapped in banana leaves, where it ferments for days. Pieces of the dough are then stirred into water to make a sour, whitish drink that is taken at meals, during work or at any hour as refreshment.

A Mexican university overview calls it a drink of Maya origin and a basic food for many peoples of southern and southeastern Mexico, among them the Chontal, Chol, Maya, Lacandón, Tzotzil (Chamula), Tzeltal, Zoque, Mam and Zapotec, as well as the mestizo population. FAO adds that it is a daily staple for large communities across social classes, and that daily intake runs from 80 to 1,000 g of undiluted dough per person.

How it is made

FAO's account begins with 1 to 1.5 kg of shelled kernels, preferably white maize, boiled for an hour in 1 to 2 litres of a solution of about 10% calcium hydroxide. The lime swells the kernels so the pericarp peels off easily, and raises the kernel pH from 5.7 to 7.5. The cooked kernels are cooled, rinsed and drained to give nixtamal, which is ground in a manual metal mill to a coarse dough.

The dough is shaped by hand into balls, typically 10 to 12 cm long and 5 to 8 cm wide, weighing 70 to 170 g, though some reach a kilogram or more. The balls are wrapped in banana leaves so they do not dry out and left to ferment for 1 to 14 days or more, depending on what the eater wants. The Mexican overview gives a wider range, from a few hours through 3 to 7 days to a month. Maize colour varies too: white, yellow or black maize are used, and the overview says people who eat all three prefer yellow and black for what they believe is more vitamin content.

What happens in the dough

Lime and heat destroy most of the microbes that come with the maize. The organisms that ferment pozol enter at grinding: lactic acid bacteria, Enterobacteriaceae and aerobic mesophiles. In the microbiology data FAO reports, the dough starts near pH 7.3 with lactic acid bacteria at 10^4 to 10^6 per gram, and in the first 24 hours the bacteria outnumber yeasts and moulds and make most of the acid. After 30 hours at 28 °C the pH had fallen to 4.6, and in a separate series the dough reached pH 3.9 by day 8, with moisture holding near 30%.

The lactic acid bacteria named include Leuconostoc mesenteroides, Lactobacillus plantarum, L. confusus, Lactococcus lactis and L. raffinolactis. The Mexican overview adds the amylolytic Streptococcus infantarius, which breaks maize starch into glucose and maltose that others can use, and a 2021 experiment compared selected amylolytic and non-amylolytic strains from pozol in pure and mixed cultures to see how they interact. Yeasts and moulds join in. FAO names Candida species, Geotrichum candidum, Trichosporon cutaneum and Saccharomyces cerevisiae among the yeasts.

Pozol also hosts nitrogen-fixing bacteria, among them Agrobacterium azotophilum, and a study of nitrogen fixation in pozol is among the sources. The overview suggests this may explain why pozol is richer in protein than unfermented maize. FAO reports pozol richer than maize in protein, niacin, riboflavin, lysine and tryptophan, and maize richer in thiamine and phosphorus. Laboratory strain studies describe how these microbes interact; they do not make those isolates a household starter.

Drinking and carrying it

Fresh or partly fermented dough is diluted with water, one part to two or three, into a porridge-like drink eaten uncooked. Salt, toasted ground chili, sugar or honey may go in. Because the balls keep, they are carried as provisions on long journeys: FAO notes that some Lacandón and Chamula travellers take fermented or mouldy balls into the forest.

The sources also report medicinal uses. The Lacandón mix pozol with honey for fever and diarrhoea, and mouldy balls have been applied to superficial wounds. FAO says laboratory tests showed in vitro antagonism against several bacteria, yeasts and moulds. Those are reports of custom and laboratory observation, not evidence of treatment.

Chorote, types and names

In Tabasco ground cacao beans are added before fermentation to make chorote; the Mexican overview also lists sugar, honey, coconut pulp and dried toasted ground chilies as additions. In Yucatán ground coconut is added. FAO distinguishes a traditional type made by indigenous people from a mestizo type that involves extra cooking of the dehulled grains, and the overview says mestizo consumers mostly take white pozol and chorote.

The word is not one thing. A study of Maya and Spanish terms argues that colonial Spanish used pozol or posole for several distinct Maya drinks, including the everyday k'eyem and the ritual saka', so the name alone does not identify one community, preparation or role. FAO records use across Chiapas, Tabasco, Campeche and Yucatán, and on a smaller scale in Veracruz, Oaxaca and Guatemala.

Safety and what is not established

FAO reports that the falling pH allows pozol to be kept without refrigeration in tropical conditions, and that antifungal substances from microbes such as Agrobacterium azotophilum may hold back mould in the first days of storage, with pH, moisture and temperature also likely to matter. The same sources record hazards. Candida parapsilosis, C. tropicalis and Phialophora richardsiae have been isolated from pozol, and the Mexican overview found Aspergillus flavus and other potentially pathogenic fungi mainly in pozol fermented for only a few hours, with more mature dough appearing to suppress them by competition. Pathogenic strains of Escherichia coli have also been found. A study cited in that overview found aflatoxins in 17% of samples, only one above 20 ppb, and none in yellow-maize pozol.

The sources do not establish a retained culture, a refresh routine, a storage period or a household safety endpoint, and nothing here should be read as a validated process. The cooking time of the mestizo type is not given.