Understanding Corn: Nixtamalisation and Why It Matters

Corn: The Foundation of Mexican Civilisation

To understand Mexican food, you must first understand corn. It is not an exaggeration to say that Mexican civilisation was built on this single crop. For over 9,000 years, corn (or maíz) has been the foundation of Mexican diet, culture, religion and identity. The ancient Maya believed that humans were literally created from corn dough by the gods - and when you taste a freshly made corn tortilla, that mythology starts to feel almost reasonable.

But here is what most people outside Mexico do not realise: the corn used in authentic Mexican cooking is fundamentally different from the sweetcorn you buy at Tesco. And the process that transforms it from a hard, nutritionally limited grain into the soft, aromatic masa used for tortillas and tamales is one of the most ingenious food technologies ever developed. That process is called nixtamalisation.

What Is Nixtamalisation?

Nixtamalisation (from the Nahuatl words nextli, meaning ashes, and tamalli, meaning corn dough) is the process of soaking and cooking dried corn kernels in an alkaline solution, traditionally water mixed with cal (calcium hydroxide, also known as slaked lime or pickling lime). The corn is then washed, the outer hulls are removed, and the resulting soft kernels - called nixtamal - are ground into masa, the dough used for tortillas, tamales, pupusas, gorditas, sopes and dozens of other Mexican staples.

The process was developed by Mesoamerican peoples somewhere between 1500 and 1200 BCE, making it roughly 3,000 years old. It is, without any hyperbole, one of the most important food processing techniques in human history.

The Chemistry Behind It

The alkaline solution (typically a 1-2% concentration of calcium hydroxide in water) does several remarkable things to the corn:

• Removes the pericarp: The tough outer hull of the corn kernel softens and can be washed away, making the corn easier to grind
• Releases niacin (vitamin B3): In untreated corn, niacin is bound in a form that the human body cannot absorb. The alkaline treatment frees it, preventing pellagra - a serious deficiency disease
• Increases calcium content: The calcium from the lime is absorbed into the corn, adding a significant nutritional boost
• Improves protein quality: The alkaline treatment makes the proteins in corn more bioavailable and improves the amino acid balance
• Develops flavour: Nixtamalised corn has a distinctive, complex flavour - earthy, slightly mineral, with floral and nutty notes - that is completely absent from untreated corn
• Creates workable texture: The starches and proteins are modified to produce a dough (masa) that is pliable, cohesive and can be pressed into tortillas without crumbling

The Pellagra Connection: A Cautionary Tale

When European colonisers brought corn back from the Americas in the 16th century, they took the grain but not the knowledge of nixtamalisation. The result was catastrophic. Populations in southern Europe and later in the American South who adopted corn as a dietary staple without nixtamalising it developed pellagra - a devastating disease caused by niacin deficiency, characterised by dermatitis, diarrhoea, dementia and eventually death.

Pellagra epidemics killed hundreds of thousands of people across Europe and America between the 18th and early 20th centuries. All because they ate corn without performing the simple alkaline treatment that Mesoamerican peoples had been using for millennia. It is a striking example of indigenous knowledge being ignored with deadly consequences.

In Mexico and Central America, where nixtamalisation was always practised, pellagra was essentially unknown - despite corn making up an enormous proportion of the diet.

From Nixtamal to Masa: The Process Step by Step

Step 1: Selecting the Corn

Traditional Mexican cooking uses field corn (also called dent corn or flint corn), not the sweet corn varieties sold as fresh vegetables. Field corn is harvested when fully mature and dried on the cob. Mexico grows thousands of native corn varieties in an astonishing range of colours - white, yellow, blue, red, purple and even black - each with its own flavour profile and best uses.

In the UK, you can find dried corn for nixtamalisation at specialist Mexican shops or online retailers. Check our UK Mexican shops directory for stockists.

Step 2: Cooking in Lime Water

The dried corn is added to a pot of water with approximately 1 tablespoon of food-grade calcium hydroxide (cal) per 500g of dried corn. The mixture is brought to a boil, then simmered for 30-45 minutes. The corn is then left to soak in the liquid (called nejayote) for 8-14 hours, typically overnight.

The soaking time is as important as the cooking. During this resting period, the alkaline solution continues to penetrate the kernels, fully transforming the starches and proteins.

Step 3: Washing

After soaking, the corn is thoroughly washed in fresh water. The loose hulls are rubbed off and rinsed away. The resulting nixtamal should be plump, tender and have a distinctive clean, mineral aroma.

Step 4: Grinding into Masa

Traditionally, nixtamal is ground on a metate - a large, flat stone with a hand-held grinding stone called a mano. This produces the finest, most flavourful masa but requires significant physical effort. Modern Mexican households and tortillerias use electric grain mills.

In the UK, you can use a hand-cranked grain mill or a powerful food processor (though the texture will not be as fine). Some Mexican shops in London sell fresh masa - check our shops directory.

Types of Masa and Their Uses

Masa for Tortillas

Tortilla masa is ground relatively fine and mixed with water to form a soft, pliable dough. It is pressed thin using a tortilla press (or two heavy books with a plastic bag between them) and cooked on a comal (flat griddle) or dry frying pan for about 30-60 seconds per side. A properly made corn tortilla should puff up slightly, have light brown spots and smell intoxicatingly good.

Masa for Tamales

Tamale masa is ground slightly coarser and whipped with lard or vegetable shortening, salt and sometimes stock until light and fluffy. It is spread onto corn husks or banana leaves, filled with meat, cheese, chillies or sweet fillings, wrapped and steamed. Browse our recipe collection for tamale recipes.

Masa for Gorditas, Sopes and Tlacoyos

These thicker corn preparations use the same basic masa as tortillas but are shaped differently - pressed thicker, sometimes stuffed with beans or cheese, and cooked on a griddle before being fried. They represent the incredible versatility of a single ingredient.

Masa Harina: The Convenient Alternative

If nixtamalising your own corn sounds daunting, there is an excellent shortcut: masa harina. This is nixtamalised corn that has been ground and then dried into a flour. You simply add water to reconstitute it into masa dough.

The most widely available brand in the UK is Maseca, which you can find at Sainsbury's, Waitrose and many Mexican shops. Bob's Red Mill also produces a masa harina available through Amazon UK and health food shops.

Whilst masa harina does not produce results quite as flavourful as freshly ground nixtamal, it is extremely good and makes corn tortillas, tamales and other masa-based dishes accessible to anyone with a kitchen and 20 minutes to spare.

Quick Corn Tortillas from Masa Harina

Mix 200g masa harina with approximately 250ml warm water and a pinch of salt. Knead for 2 minutes until smooth. Divide into golf-ball-sized portions. Press between two sheets of cling film using a heavy pan or tortilla press. Cook on a very hot, dry frying pan for 60 seconds per side. They should puff slightly and develop light brown spots. Makes about 12 tortillas.

Why Corn Tortillas Taste Different from Flour Tortillas

If you have only ever eaten flour tortillas from a supermarket packet, you may wonder what all the fuss is about. Flour tortillas are fine - they are soft, neutral and functional. But corn tortillas are something else entirely. They have a complex, earthy flavour; a slightly chewy texture; and an aroma that is genuinely one of the great smells in cooking.

The difference comes entirely from nixtamalisation. The alkaline treatment creates flavour compounds that simply do not exist in wheat flour or untreated corn. When you heat a corn tortilla, those compounds become volatile and aromatic, filling the kitchen with a warm, mineral, almost popcorn-like smell.

Corn in Mexican Culture

Corn is not merely food in Mexico - it is identity. The Popol Vuh, the creation story of the Maya, describes humans as being fashioned from white and yellow corn after failed attempts with mud and wood. Today, Mexico is home to 59 native corn races and thousands of varieties, many of which exist nowhere else on earth.

This biodiversity is threatened by industrial agriculture and genetically modified corn imports. Many Mexican farmers, chefs and activists are working to preserve native corn varieties, and a growing nixtamal movement is bringing fresh-ground masa back to restaurants and homes.

Where to Buy Corn Products in the UK

For masa harina, dried corn, and nixtamalisation supplies in the UK, visit our Mexican shops directory. Online retailers like Mexgrocer and Cool Chile Co stock masa harina, dried corn varieties, and even food-grade calcium hydroxide for those who want to try nixtamalising at home.

Understanding nixtamalisation transforms your appreciation of Mexican food. Every tortilla, every tamal, every gordita represents thousands of years of culinary knowledge - and now you know the science behind the magic.