First of all, if you have never prepared food from home-grown and home-ground field corn, such as grits, cornbread, or corn tortillas; there is no comparison to store-bought.  For me, the taste difference is at least as dramatic as that with winter tomatoes and garden-fresh.

Start with dry field corn kernels.  This is NOT the same thing as sweet corn.  Field corn, also referred to as dent corn, is harvested when dried in the fall, and is a variety that is higher in starch and used for cornmeal and the like.  Sometimes this is sold as (gasp) a decorative corn.  If you don’t have ready access to dried field corn, try growing your own.  Look to future posts for more on growing field corn.

You will also need hardwood ash that has been sifted to filter out the chunks of char that are not fully burned pieces of wood.  Be mindful of where your ashes come from – be sure no pine or cedar were burned, or worse (plastics, etc.).  You can filter with mesh wire, a large mesh strainer, etc.  You need as much ash, by volume as corn kernels you will cook.

Step 1: Soak

Different sources suggest various durations of time to soak in just water prior to mixing with ash-water, ranging from an hour to 24 hours.  We've tried the full range and found this makes no difference in our experience, so soak for as little or as long as is convenient.

The water we use to soak the corn is kept in the pot and ash will be added to this.  The amount of water we have read to use is 1/2 gallon water to 2 cup corn.  I guess that's 16:1 volume ratio water to corn.

Step 2: Mix with ash

We use a 1:1 ratio of ash to corn (measuring volume).  Like a lot of cooking, there is a both a learning curve and a bit of an art.  You want to ensure the mixture is liquidy during the whole process.  The ash won’t exactly dissolve, but you need enough water to keep it suspended in a liquid.

Ash water at this concentration is alkaline, but not strong enough to be considered lye or to do damage to your skin.  The process of mixing corn with ash-water or another alkaline solution such as food-grade lime (calcium hydroxide) is called nixtamalization, and is a centuries old traditional method of preparing maize, or field corn that originated in Mesoamerica.

Nixtamalization breaks down the hard cell walls of corn and releases the pectin inside, allowing the resultant corn flour to bind into a cohesive dough and not crack when prepared and cooked. The corn also puffs up better and intensifies in flavor.  And if that’s not enough, nixtamalization makes the corn more nutritious to boot.  It creates resistant starch, which has a lower glycemic index and promotes healthy gut bacteria, and it increases the bioavailability of iron, calcium, vitamin A, and niacin.  Last, nixtamalizing corn vastly reduces any potentially dangerous aflatoxin on the corn. 

Step 3: Heat to cook

You want to boil for about an hour.  During cooking, water evaporates, and you'll likely need to add more water to keep the mixture from becoming too thick or even concrete-like at the bottom of the pan.

The ash will settle during cooking, so stir periodically to keep the ash from settling and forming a thick crust on the bottom of the pot.

As soon as the water gets hot, our yellow field corn turns a vivid orange color, and after another 5 minutes or so, the color reverts to the original color, which is all cool, and we've read a sign that the water was the correct strength.

Step 4: Check for doneness

When you have cooked for nearly an hour, you'll start to see the clear corn skins beginning to come off and float.  There is also a dark spot on each kernel at the point where the kernel attaches to the cob.  This too will come loose and fall off.  When that happens, take a kernal out, rinse it in cold water, and conduct a bite test.  Look for it to be fairly soft - not squishy soft, but a good bit of give.  Kinda like pasta. This too requires some experience and experimentation.  On our first batch, the kernels broke up altogether.  We dried it and ground it anyway, but you want to stop cooking before it gets to this point.

Step 5: Rest

When done cooking, let the whole mess sit for an hour.  Then rinse:

Step 6: Rinse

Pour the mess through a colander and start rinsing.  Johnny puts his hands in it, and gently rubs the kernels to get the last of the skins off, and rinses like crazy to get all the ash off.  The whole mess starts off grey - there is a crazy amount of ash.  Don’t freak out.  It will all rinse away.  You can taste it for quality control at this point.  You'll be able to tell if there is still ash in the mix even when you can’t see any, it tastes like ash :)  Rinse until it is clean, clear, and tastes like corn.

Step 7:  Dry and grind

After it is rinsed, spread out the kernels and dry.  They need to be dry inside and out prior to grinding (unless you own a wet grinder).   We dry ours by hanging them on vented trays above our wood stove.  You could also use an electric dehydrator or other means.

Grind the corn as fine as flour.  We grind in a hand grain mill.  The coarse corn mill we have doesn’t grind it fine enough.

The masa harina, or nixtamalized corn flour, is now shelf stable and ready for you to transform it into the most delicious corn tortillas you have ever eaten.