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

Abstract

Cereal Chem. 87(5):434-438Degradation of added folic acid and native folates in micronutrientfortified 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.

Evaluation of Bacterial Effects on Folic Acid Loss in Fortified, Nixtamalized Corn Masa Flour

“…To quickly determine if there were folate-requiring organisms among the mill isolates, the standard microtiter plate folate assay, used by Chapman et al (2010), was modified to allow evaluation of microbial folate dependence. To quickly determine if there were folate-requiring organisms among the mill isolates, the standard microtiter plate folate assay, used by Chapman et al (2010), was modified to allow evaluation of microbial folate dependence.…”

“…For each mill treatment, 1 mL of each of the appropriately diluted individual organism cultures designated in Table I was then added to a small amount of sterile water and brought up to 110 g with addition of sterile water. This holding temperature was used based on the finding of Chapman et al (2010) that 50 kg masa dough bundles evaluated in a commercial mill remained near the mill exit temperature (56°C) for up to 4 h. After incubation, samples were immediately frozen at -40°C and analyzed for folic acid content. Control samples were prepared by mixing irradiated corn masa flour with 110 g of sterile water.…”

“…In tests done by Dunn et al (2008) at a commercial tortilla mill in Guadalajara, Mexico, a micronutrient premix was added to the nixtamal just before it was ground into masa. In a subsequent study, Chapman et al (2010) observed a 73% w/w reduction in folic acid in fortified, nixtamalized masa during a 4 h holding period before baking. Almost all of the reduction in folic acid resulted after the nixtamal was fortified and before baking, indicating that the degradation process was happening in the prebake masa during holding.…”

Isolation and characterization of the microflora of nixtamalized corn masa

“…Traditionally, corn tortillas are prepared by steeping whole-kernel corn in a hot, alkaline solution, containing 1.5-2% lime (CaO), and subsequently grinding the drained and rinsed corn (now referred to as nixtamal) into a fresh dough called masa. The ground masa typically exits the grinding stones at a temperature near 56°C (Chapman et al, 2010). Tortillas are produced using this process in tens of thousands of very small neighborhood mills scattered throughout towns and cities across Mexico and Central America.…”

“…In commercial tortilla mills, the hot masa is often stacked and stored in large pails or sacks at ambient temperature for anywhere from a few minutes to several hours before being formed into tortillas and baked (Chapman et al, 2010). Due to the availability of nutrients, the high moisture content (approximately 56%) (Ramirezwong et al, 1994), and warm storage temperature, significant microbial growth can occur while the masa is being held for extended periods.…”