Stability of Native Folate and Added Folic Acid in Micronutrient-Fortified Corn Masa and Tortillas

Degradation of added folic acid and native folates in micronutrient-fortified corn masa and tortillas was evaluated using masa prepared from either nixtamalized corn flour or fresh nixtamal. Variations in masa pH, masa holding time at an elevated temperature, and iron source failed to show significant differences in folate loss in corn flour masa prepared in the laboratory. Masa was subsequently prepared from fresh nixtamal in a commercial mill in Mexico, and fortified with one of two different micronutrient premixes containing iron, zinc, B-vitamins, and either unencapsulated or lipid-encapsulated folic acid. Folate loss in commercial masa increased significantly with prebake masa holding time for both premixes. Unencapsulated folic acid showed a 73% loss after 4 hr of holding, compared to 60% loss for encapsulated. The difference was statistically significant, indicating a protective effect from the lipid coating. No significant differences in folate levels were found between prebake masa and baked tortillas. Holding baked tortillas for up to 12 hr also had no effect on folate levels. Native folate showed no significant losses throughout the process. Results from the commercial tortilla mill indicate that most of the loss in added folic acid occurs during prebake holding of masa, possibly from microbial degradation.