In recent years inspectors have become increasingly concerned about traditional nixtamalization methods. Many tortilla manufacturers across the US have had inspectors make them through away steeping corn. During inspections many tortilla manufacturers have been unable to demonstrate the safety of the steeping process to regulators. The inspectors concern is two fold. First they are concerned about the safety of the nixtamalization process, which lacks time and temperature controls and relies solely on pH for microbiological pathogen control. Second, as the regulations are currently written there is an exemption for acidified foods from time temperature controls but not for alkaline foods like nixtamalized corn. Tortilla manufacturers have been able to demonstrate the safety of the nixtamalization process to inspectors with the flow chart we have prepared (contact us for a free copy).
We have offered this resource to regulatory agencies across the country for several years and have always had them agree with our analysis at the end of the day. In particular, that the alkaline pH of the Nixtamalization process, which is typically around pH 11 to 12, does not permit the growth of pathogens (see table from the FDA’s website below). We agree that there is a point after steeping, after the rinsing of the corn, that there is a time/temperature concern.
FDA’s Safe Practices for Food Processes: Chapter 3. Factors that Influence Microbial Growth
| Table 3-5. Approximate pH values permitting the growth of selected pathogens in food. | |||
| Microorganism | Minimum | Optimum | Maximum |
|---|---|---|---|
| Clostridium perfringens | 5.5 – 5.8 | 7.2 | 8.0 – 9.0 |
| Vibrio vulnificus | 5.0 | 7.8 | 10.2 |
| Bacillus cereus | 4.9 | 6.0 -7.0 | 8.8 |
| Campylobacter spp. | 4.9 | 6.5 – 7.5 | 9.0 |
| Shigella spp. | 4.9 | 9.3 | |
| Vibrio parahaemolyticus | 4.8 | 7.8 – 8.6 | 11.0 |
| Clostridium botulinum toxin | 4.6 | 8.5 | |
| Clostridium botulinum growth | 4.6 | 8.5 | |
| Staphylococcus aureus growth | 4.0 | 6.0 – 7.0 | 10.0 |
| Staphylococcus aureus toxin | 4.5 | 7.0 – 8.0 | 9.6 |
| Enterohemorrhagic Escherichia coli | 4.4 | 6.0 – 7.0 | 9.0 |
| Listeria monocytogenes | 4.39 | 7.0 | 9.4 |
| Salmonella spp. | 4.21 | 7.0 – 7.5 | 9.5 |
| Yersinia enterocolitica | 4.2 | 7.2 | 9.6 |
Sources: Table 5.3 in ICMSF 1980, p 101.
1pH minimum as low as 3.8 has been reported when acidulants other than acetic acid or equivalent are used.
Just had this come up again at a local Tortilleria in LA County. Let me know if anyone has any other questions about this.
Good information on the nixtamalization of Maiz and the need to educate many of the inspectors that are keeping tortilleros from cooking corn… I’m a firm beliver of cooking corn for both tortillas and tortilla chips… we provide cooking systems for many food companies… corn / maiz is but one of them… Take care.