Micronutrient fortification has little impact on properties of nixtamal corn tortillas.

Nixtamalization is the process by which dry maize grain is soaked and cooked in an alkaline solution, usually limewater, to cause the transparent outer hull, the pericarp, to separate from the grain. This process allows the grain to be more effectively ground; increases its protein and vitamin content availability; improves its flavor and aroma; and reduces levels of mycotoxins. The resulting product is called nixtamal and is further processed into tortillas.

It is estimated that 60% of the corn tortillas in Mexico are produced from fresh nixtamal. The rest are prepared from nixtamalized corn flour. While some corn flour in Mexico is fortified with micronutrients, nixtamal-based tortillas are not.

Scientists at Brigham Young University evaluated the nutrient stability and other quality parameters of fortified corn tortillas made from fresh nixtamal. Results of their work indicate that fortifying this product can significantly improve its nutritional content without significantly affecting its sensory acceptance and other properties.

The researchers fortified nixtamal with a micronutrient premix that contained iron, zinc, folic acid, niacin, riboflavin and thiamin. They used the same premix with salt, which was added as a marker to aid in the rapid testing of the premix concentration.

The premix composition was based on a proposed Mexican regulation for flour fortification, adjusted for moisture. The researchers measured the effect of the premix addition on masa adhesiveness, hardness and pH, as well as on tortilla sensory properties: rollability, stretchability and color. Micronutrient levels were tested in the dry corn, nixtamal, masa and tortillas.

No significant differences in sensory attributes were found among the control, the micronutrient premix tortillas and the tortilla with the same premix with salt. Any added thiamin was almost entirely degraded during the initial mixing stage. Folic acid and riboflavin levels significantly decreased 26% and 46%, respectively, during the masa-tortilla manufacturing process.

There was no significant loss of niacin. Adding salt had no significant effect on the stability of the micronutrients. With the exception of thiamin, fortification significantly increased nutrient levels from those that were in the control tortillas. Folic acid levels increased 974%. Niacin increased 171%. Riboflavin increased 317% in the micronutrient premix tortillas. Iron and zinc levels increased 168% and 92%, respectively. Researchers indicate that you may have to fortify with a little more thiamin than first planned, or encapsulate the thiamin so that it can withstand the moist, alkaline environment.

Further information. Michael Dunn, Department of Nutrition, Dietetics and Food Science, Brigham Young University, S129 ESC, Provo, UT 84602; phone: 801-422-6670; fax: 801-422-0258; email: michael_dunn@byu.edu.