Sources of microorganisms in pozol, a traditional Mexican fermented maize dough

Area of Science:

• Food Microbiology
• Fermentation Science
• Traditional Food Processing

Background:

• Pozol is a traditional Mexican fermented maize dough with significant cultural and nutritional value.
• Understanding the microbial dynamics during pozol preparation is crucial for ensuring its safety and quality.

Purpose of the Study:

• To characterize the microbial populations present in freshly prepared and fermented pozol.
• To identify the key processing stages that contribute to the microbial flora of pozol.
• To investigate the changes in microbial counts and pH during pozol fermentation.

Main Methods:

• Enumeration of microbial groups including lactic acid bacteria, aerobic mesophiles, Enterobacteriaceae, yeasts, and moulds using colony-forming units (c.f.u./g wet wt).
• Monitoring microbial populations and pH over a 30-hour incubation period at 28°C.
• Assessing the microbial contribution of different processing steps: soaking, grinding, dough handling, and environmental factors.

Main Results:

• Fresh pozol contained significant levels of lactic acid bacteria, aerobic mesophiles, Enterobacteriaceae, and yeasts.
• After 30 hours of fermentation, lactic acid bacteria and yeasts showed a substantial increase (up to 10(9) and 10(6) c.f.u./g, respectively).
• Soaking alkali-treated grains and grinding were identified as the primary sources of microbial inoculation, significantly influencing the dough's flora.
• The pH of pozol decreased from 7.3 to 4.6 during fermentation.
• Enterobacteriaceae and aerobic mesophilic bacteria populations remained stable despite the decreasing pH, indicating tolerance to acidic conditions.

Conclusions:

• The microbial composition of pozol is primarily determined by the initial microbial load from soaked grains and the inoculation during grinding.
• Fermentation leads to a dominance of lactic acid bacteria and yeasts, characteristic of traditional fermentation processes.
• The established microbial community in pozol exhibits resilience to the acidic environment generated during fermentation.