Microbiology of Indian and Mestizo pozol fermentations

Pozol is a beverage prepared from fermented nixtamal consumed in Southeastern Mexico. The Mestizos have modified the traditional Indian procedure by adding an extra cooking step to reduce the amount of solid sediment present in the beverage when the dough is suspended in water. To elucidate whether this additional step influences the microbiology of the fermentation the microbiota before fermentation of Indian and Mestizo nixtamal doughs, and the microbial growth during both processes were assessed. The initial microbiotas of freshly made nixtamal doughs purchased on nine successive days from one Indian producer and one Mestizo producer were examined. The numbers of microorganisms in the initial doughs were quite constant day by day and were similar in the Indian and Mestizo products, initial microbial concentrations (cfu g(-1)) were: lactic acid bacteria, 70(5)-10(6); non-lactic aerobic mesophilic bacteria, 10(4)-10(6), enterobacteria, 10(3)-10(4); mould propagules, 10(2)-10(3) and yeasts, 10(4). In the products fermented at 28 degrees C for 48 h the concentrations of lactic acid bacteria and non-lactic aerobic mesophilic bacteria were 10(9) and 10(5) cfu g(-1) respectively. No differences were found in the initial microbiotas nor in the fermentation patterns of both kinds of doughs. The concentrations of bacteria were similar on the surface and in the interior of the bails, but those of moulds and yeasts were higher on the surface than in the interior. In spite of the low pH values attained (4.5 or below), viable enterobacteria were still present at the end of the fermentation. (C) 2000 Academic Press.