Nixtamalization is a centuries-old process originating in Mexico and Central America that improves the nutritional quality of corn grain. A complex physical-chemical process that has managed to reduce pellagra disease in these American regions. Nixtamalization is a process by which corn is cooked with water and lime to obtain nixtamal: already cooked grains that once ground will be used to make different typical South American dishes such as tortillas, arepas, pozole or tamales.
What is nixtamalization and what is it used for?
Nixtamalization is a process by which raw corn is cooked in a solution of water and calcium hydroxide (food-grade lime, harmless and safe) to improve its nutritional quality. This produces the so-called nixtamal, corn kernels that are the basis of basic foods in American cuisine. The process improves the nutritional quality of raw corn, adding calcium and helping the proper assimilation of its nutrients. Although of pre-Columbian origin, nixtamalization is a very common procedure in Mexican and Central American cuisines that is still used industrially today.
Its origin is a clear example of the search to improve the conditions of the time: After the importation of American corn to Europe, cases of pellagra increased considerably, a disease that many know as the 4 D disease (dermatitis, diarrhea, dementia and death) and which is caused by a lack of niacin, or vitamin B3, whose precursor is tryptophan.
Nixtamalization, as we will see, allows the release of glutelin and makes niacin available. Without this process, diets based on corn would cause the development of this disease, which is very common in other parts of Latin America and Europe for centuries and yet has a lower incidence in Mexico and Central America.
The word nixtamalization comes from Nahuatl—a dialect spoken by more than three million Mexicans today—where “nextli” means “ashes” and “tamali” means unformed corn dough. The name refers to the way corn was nixtamalized in ancient times, even before there was a scientific answer to the process: by cooking it in a mixture of water and ashes.
How the nixtamalization process is carried out
To carry out nixtamalization, raw corn is needed, which is poured over a basic solution with a pH between seven and fourteen. The compound that will allow this alkaline solution to be created is Ca(OH)2, better known as calcium hydroxide. Thus, in a 1:3 ratio —one kilo of raw corn for three liters of an alkaline solution—, the grain is cooked until the nejayote —as the boiling solution is known— rests for more than 12 hours, a time that varies depending on the recipe, as there are many.
The high temperatures achieved during cooking, together with high pressure, allow the outer layer of the corn kernels to break, causing the husk to loosen. Through a process of chemical balance, calcium ions penetrate the corn, thereby achieving a higher concentration of calcium in the kernels, which is vital for improving the organoleptic and nutritional conditions of the cereal.
Calcium hydroxide or slaked lime, nothing to do with quicklime
Lime is used for nixtamalization, but not just any kind of lime. A type of lime suitable for human consumption is used, the so-called food-grade lime or calcium hydroxide with a purity of over 90%, which can be safely consumed in the right quantities. Not only is its consumption not dangerous, but, as far as nixtamalization is concerned, it is nutritionally beneficial due to the chemical changes it produces in the corn.
Calcium hydroxide is a type of treated lime that is safe for human consumption. Lime is a material obtained by cooking limestone at 1000 degrees with natural gas to obtain quicklime or calcium oxide. When quicklime is hydrated with water and cooled, it becomes slaked lime or calcium hydroxide, suitable for human consumption as long as it is of high purity and processed following strict regulations that ensure that it is a product free of any type of heavy metal contamination. We should not confuse quicklime with lime for food use.
In the food industry, additives are numbered so that they can be easily identified throughout the world. For example, calcium hydroxide has E526 as its reference. This additive, vital in food, hardens food and allows it to be preserved for longer, as we have seen with corn grain.
Why is corn nixtamalized? Benefits
Corn is the staple grain of the American diet. Therefore, it was necessary to have a process that would not only allow for an improvement in the preparation times of corn derivatives but also a method that would make their conservation much longer. In addition to the improvements in flavor, texture, and nutritional value, they can be preserved for longer. A change that has an impact on the conception of corn as a fundamental part of Mexican and Central American cuisine.
Zein and glutelin are two of the main proteins found in corn. They are macromolecules that have hundreds of small “bricks” that are joined and assembled; these bricks are amino acids. Zein, in addition to its unexpected projection in the field of biotechnology, contains a very low concentration of lysine and tryptophan – amino acids that intervene in the production of collagen and in the sleep cycle, respectively. Thus, zein is considered to be of low nutritional quality. The nixtamalization process causes its solubility to decrease while the solubility of glutelin increases. The latter is rich in the two amino acids mentioned, which makes it the main cause of this entire physical-chemical process.
Furthermore, unnixtamalized corn grain contains high concentrations of phytic acid, a type of compound that prevents the absorption of calcium and magnesium in the body. The physical-chemical process of nixtamalization reduces phytic acid, causing calcium to bind efficiently to starch, making it easily absorbable by the intestine.
A higher concentration of calcium ions in treated corn allows for an improvement in the nutritional conditions of the cereal. This increase in the concentration of calcium ions translates into an increase in the generation of collagen as well as a greater production of hormones and synaptic improvements, given that calcium in its ion form is vital in neurological processes.
Contraindications and risks of nixtamalization
Nixtamalization is a process that should not involve any risk as long as the appropriate precautions are taken and the proportions are respected, taking into account the characteristics of the corn kernels, especially their hardness. It can be done at home by buying food-grade lime and protecting yourself to prevent dust from getting into your eyes or through the respiratory tract. Although contact with the skin is less dangerous, it is also advisable to wear gloves and avoid direct contact. It must be kept free of moisture and away from sources of CO2.
The dangerous part is processing calcium oxide to obtain calcium hydroxide, as this produces an exothermic reaction that can cause burns. For this reason, from the 1930s onwards, the commercialisation of calcium hydroxide was industrialised, thus avoiding the risks associated with its production for the population.
In any case, it is always necessary to check the origin of the lime used, because unfortunately in unregulated markets there is the possibility that lime is being used that does not meet the necessary quality standards or is not suitable for human consumption.