Study: Foods Made With Whole-Grain Zinc Maize Lose Only Small Share of Zinc in Processing, Cooking
Maize is the most-consumed cereal in several Latin American countries. In Mexico and Central America, more than 600 food products and dishes are derived from maize.
Many of these maize dishes use the ancient cooking process called nixtamalization, which consists of boiling and steeping whole maize grains in an alkaline solution. Tortillas are the most-consumed product prepared from nixtamalized dough, and today tortillas are found worldwide.
A recently published study looked at the effects of processing and cooking methods on zinc content in common dishes that were made with zinc-biofortified maize. The dishes included tortillas, arepas (cornmeal cake), and mazamorra (maize porridge). Only the maize used for the tortillas was nixtamalized; the maize for the arepas and mazamorras was processed differently.
The study showed that zinc (as well as iron) losses in the tortillas after the nixtamalization process were small. Zinc losses in the arepas and mazamorra were greater, likely because these products are produced with dehulled and degermed maize, stripping out more of the nutritious parts of the maize grain.
Indeed, the study authors note that most of the zinc in the maize grain is located in the middle of the grain. Nixtamalization preserves more of the grain and only strips away part of the outer layer, leaving the zinc intact.
The authors concluded that one way to improve zinc intake in this region would be to promote consumption of nixtamalized tortillas made of high-zinc maize. For the same reason, they also recommend using whole-grain flour to make arepas because it contains more zinc. While this is not the most common way of preparing arepas, they cite recent health-conscious trends that may create consumer demand for whole-grain products over highly processed ones.
The lead study author, Sonia Gallego, said: “This study confirms that the additional zinc found in biofortified maize results in nutritional benefits for consumers who eat foods made from it.”
The study notes that the contribution of zinc maize to the estimated average requirement (EAR) would be up to 76 percent for children ages 4–6 years and 89 percent for women of child-bearing age when eaten as the main staple in the form of minimally-processed products like tortillas.
However, the EAR contribution would be only 34–44 percent if consumed as arepa or mazamorra because the process removes the germ and pericarp of the grain, which contain most of the zinc. That said, the zinc bioavailability in processed arepas and mazamorra could be higher compared to tortillas due to the lower antinutrient (phytic acid) concentration in threshed grain used to make these products.
In Mexico, 33 percent of children younger than 5 years are zinc deficient. Zinc is vital for survival, meaning a deficiency has serious consequences for health, particularly during childhood when zinc requirements are increased. In addition, zinc deficiency is associated with stunting and increases the risk of common childhood infections including diarrhea, pneumonia, and possibly malaria.