Until wheat was introduced to the Americas the primary grain was (and still is really) corn. Corn, botanically known as Zea mays, is native to Mexico and there are hundreds of species in a wide range of colours each with slightly different nutritional values.

Ground masa on a metate

It is the nutritional value of corn that is the most interesting. Corn can be difficult to digest and a kernel of corn can pass through the digestive tract completely unharmed. Some of the nutrients are bound tightly within the kernel and consuming only untreated corn can cause a disease called Pellagra due its nutrients being unavailable for absorption by the body. In this case we are discussing vitamin B3 or niacin.

When corn was initially exported to areas wheat would not grow it was readily taken up by the farmers on those lands and soon became the grain of choice. Pellagra, a disease of nutritional deficiency (1) followed soon after as although the Spanish had exported the corn they had not exported the science behind treating it and turning it into a viable foodstuff. Pellagra is an Italian word that references the roughened skin which develops later (particularly on the face) in the course of the disease (2). Symptoms range from chronic dermatitis, diarrhoea, dementia, and if left untreated, can result in death.

  1. in a vein similar to scurvy
  2. sufferers of pellagra where sometimes known as the “butterfly people” due to the symmetrical butterfly shaped rash that first appears on the nose and face before spreading, painfully, to the rest of the body

Corn was consumed daily by the Mesoamericans in the form of the humble tortilla but before it could be ground into a nutritious (1) and pliable paste it was treated through a process called nixtamalization. This entailed cooking the corn in a fairly alkaline solution, allowing it to rest in the liquid until the pericarp (the outer layer of the kernel) loosened which was then removed by rubbing/washing it off in clean water. The exposed kernels could then be ground into a soft paste called “masa” on a volcanic grinding stone called a metate. This was hard work.

  1. and consequently avoiding the problems of pellagra
Mother teaching daughter how to make tortillas. Codex Mendoza

Nixtamalizing corn does more than just removing the hull (pericarp) of the corn allowing it to be ground into a pliable dough. The alkaline solution used will remove the potential danger of mould producing aflatoxins which sometimes grow on the stored grain which can cause health issues including stunted growth in children and acute hepatic necrosis in those susceptible. As previously mentioned, the process of nixtamalisation also liberates B vitamins bound within the grain and alters the amino acid profile of the grain balancing it out somewhat and it enriches the mix with vital minerals such as calcium, zinc, iron, and magnesium.

The process of nixtamalization is fairly simple. You will need:

  • 1 kilogram clean, dried flour-corn kernels (about 2 pounds)
  • 1/4 cup pickling lime (food-grade calcium hydroxide – “slaked lime” – called “cal” in Mexico)
  • 3 litres water (12 cups)


  • Rinse the corn in a colander and set aside.
  • In a large, stainless steel (nonreactive) pot, dissolve the lime in the water. Immediately wash off any lime that gets on your hands as it may burn your skin.
  • Add the corn and discard any floating kernels. Bring to a boil over high heat. Reduce the heat to low, and cook uncovered for 30 minutes. Turn off the heat and let it sit, uncovered, overnight in the refrigerator.
  • Transfer to a strainer and wash the corn under cold running water, rubbing it vigorously between your hands, until most of the skins have come off and the kernels look shiny (don’t use a fine-mesh strainer, as you want the skins to fall to the bottom of the strainer or slip away through the holes).
  • To make a finer masa pinch off the pedicel before grinding them into a paste. (this is called deheading) The pedicel is a dark spot at the base of the kernel. Doing this will increase the preparation time needed to produce your masa. It is not a necessary step and will not negatively affect your masa in any major way (there will be dark speckles in the masa).
  • Use the corn immediately or store fully covered in fresh, cool water for up to 1 day in the refrigerator.
  • Drain well.

Use the whole, moist kernels in soups or stews – corn treated like this is called posole or hominy. Or, grind them through a food mill to make masa. If making tortillas, grind the masa once more in a stone grinder (metate) to get a fine, smooth consistency. Refrigerate any unused masa, and use it within 3 days as it can become too sour to eat. Grinding masa on a metate can add some extra nutritional value to the corn and if the metate is only washed with water it will add a probiotic factor. DO NOT wash your metate (or molcajete) with soap as it will permeate into the volcanic rock and will flavour everything ground on (or in) it.

Not all varieties of corn are suitable for nixtamalization. There are five main varieties of corn, flint, dent, flour, sweet and popping. Sweet corn and popping corn are the two main types you are likely to be familiar with and possibly the only two you have seen if you live outside the Americas. Flint and dent corns are used for stock feed and flour corns are used for, well, flour. The last three corns mentioned are all suitable for converting into masa although there will be a wide range of variation between the masas they produce. Masa can also be dried into a flour called masa harina which can then be used to make tortillas and a million other things.

Nixtamalised corn showing separation of pericarp.
The pedicel  of the kernel is the dark spot at the bottom. This is where the kernel attaches to the cob.     

Wood ash can be used instead of cal to alkalinise the water. The flavour of the masa will be changed somewhat depending on the ash used. Many colonists witnessed the use of wood ash or wood ash lye when Indians cooked maize, but did not interpret the practice as either similar to the use of cal in Mesoamerica, nor as an important culinary practice. Instead, they interpreted the practice solely as one used to flavour the corn which gave it a taste that many Europeans found distasteful.

Once the ash, cal, water and corn are mixed together and cooked as above you will have a mixture that looks a little something like this.

Cuanesle (Maize Cooked with Wood Ash)

(adapted from Oaxaca al Gusto, Diana Kennedy 2010)

Traditional of cooks in the Valley of Oaxaca will prepare cuanesle, a type of masa, to thicken moles or for some types of tamales. The preparation of the corn differs from that of masa for tortillas in that the corn is cooked with wood ash instead of lime.

Makes about 850g (about 2 pounds) masa

  • 500g  (about 1¼ pounds) white corn
  • 750ml (3 cups) wood ash
  • 750ml (3 cups) water


  • Rinse the corn and then strain off any foreign material.
  • In an earthenware pot mix the ash with the water and heat until well incorporated.
  • Add the corn.
  • Over low heat, stir constantly to make sure the mixture does not stick to the pot. Cook for about 35 minutes. The grains of corn will take on a dark colour.
  • Rub the corn to remove the skins under clean running water (or in a bucket of water with several changes of water.
  • Let it soak for about 15 minutes and then rinse it twice more in a strainer.
  • Grind it until smooth on a metate or in a mill

In Morelos and Guerrero tamales de ceniza (ash tamales) are made by nixtamalising corn with woodash (and a little cal).

Ingredients (for 10 people)

  • 10 litres of water
  • 2 kg of corn
  • 2 kg of ash
  • 50 g of lime

Allow the corn to cool in the ashen liquid before washing and grinding it.

This masa is then used to make tamales which may then wrapped in banana leaf and steamed as is usual. These tamales are generally not stuffed with any filling and are typically served with a green mole.


  • Vázquez-Carrillo, María Gricelda; Santiago-Ramos, David; Domínguez-Rendón, Edith; Audelo-Benites, Marco Antonio (2017). Effects of Two Different Pozole Preparation Processes on Quality Variables and Pasting Properties of Processed Maize Grain. Journal of Food Quality, 2017(), 1–15. doi:10.1155/2017/8627363

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