Microbiology of Indian and Mestizo pozol fermentations

Pozol is a beverage prepared from fermented nixtamal consumed in Southeaste rn Mexico. The Mestizos have modified the traditional Indian procedure by a dding 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 mi crobiota before fermentation of Indian and Mestizo nixtamal doughs, and the microbial growth during both processes were assessed. The initial microbio tas 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 wer e similar in the Indian and Mestizo products, initial microbial concentrati ons (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 propa gules, 10(2)-10(3) and yeasts, 10(4). In the products fermented at 28 degre es C for 48 h the concentrations of lactic acid bacteria and non-lactic aer obic mesophilic bacteria were 10(9) and 10(5) cfu g(-1) respectively. No di fferences were found in the initial microbiotas nor in the fermentation pat terns 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 ye asts were higher on the surface than in the interior. In spite of the low p H values attained (4.5 or below), viable enterobacteria were still present at the end of the fermentation. (C) 2000 Academic Press.