Many of the most important foods we eat are in the form of seeds. Nuts are seeds; peas and beans are seeds; and, of course, grains are seeds as well. Corn looks rather different from more conventional grains like rice and wheat, but it has the same basic anatomy as those other global staples. You don't need to know how a maize seed is put together to cook corn and enjoy it, but knowing more about the food you eat is never a bad thing.
A Brief History of Maize
The grain we call corn is more accurately called maize — "corn" was used in English for anything small and grain-like, even peppercorns — and it's thought to have been cultivated in Mexico for something close to 9,000 years. Maize was originally a freak mutation of a wild grass called teosinte, which produces relatively few kernels and locks them up in a ridiculously hard shell. That genetic quirk changed the hard shell to soft, leafy husks, and it increased the size and number of kernels on each ear.
This new and improved plant quickly became a staple food wherever it was grown — our word maize is a corruption of the native word mahiz or mahisi, meaning "that which sustains us" — and it spread throughout the Americas as far north as New England. It was introduced to Europeans in Central and North America quite early in the Colonial era, becoming equally important for the white settlers, and it was adopted with enthusiasm in parts of Europe as well.
The Parts of a Maize Plant
The maize plant is a familiar sight in the Americas, so most people know its anatomy in at least a general way. Like bamboo, it's a very large grass, with thick stems that can be taller than a person when full grown. The long leaves are much the same shape as any normal blade of grass, but much larger. The tassels at the top of the plant produce the pollen, which fertilizes the ears that grow from the plant's stem. Each of the fine threads of silk on an ear of corn corresponds to one of the grains inside.
The papery husks that grow around the ears of grain have many uses in their own right. The most important, for culinary purposes, is as a wrapping for food. Tamales are steamed inside a cornhusk wrapper, and they're also useful for fish or other delicate foods you might want to steam, bake or grill. The husks give your foods a pleasantly grassy, slightly sweet and nutty flavor, with just a hint of corn taste as well.
Three Main Kinds of Corn
There are three main kinds of corn growing in fields and home gardens. One is "flint" corn, the colorful kind used for holiday decorations and colored tortilla chips. Popcorn is a variety of flint corn, as well. The name, as you might imagine, comes from the hardness of the kernels. Dent corn, used as fodder for animals and a raw ingredient for industrial manufacturing, earns its name from the small indentation that's visible on each kernel.
The kind of corn you're likeliest to grow in your home garden is sweet corn, another happy mutation that has a sort of prolonged adolescence. The sugars in the immature grain stay sweet and soft for an extended period before they finally turn to starch and harden. That's the kind that comes to the table as corn on the cob or as a frozen vegetable. Although the three kinds of maize have different characteristics, their anatomy is identical in most ways.
The Parts of a Maize Seed
If you look at a diagram of a maize seed, the first thing you'll see is the outer seed coat, or pericarp. Underneath that is a very thin layer called the aleurone. Inside the kernel, at the narrow tip, you'll find the germ of the seed, which itself is made up of a number of smaller components. In between, you'll find the endosperm, the sweet or starchy substance that gives the seed most of its bulk. Each of those parts of the maize seed has a functional role in growing new plants, and also a culinary significance.
The Seed Coat
The seed coat contains the two outer layers of the kernel, the pericarp and the aleurone. Their primary role is to protect the seed itself, so it can survive until spring and produce a new plant. The pericarp's tough fiber forms a shield to protect the nourishing seed inside from mold and bacteria, as well as from livelier threats such as insects and grazing herbivores. The role of the aleurone isn't as clear or obvious, but it's known to contain a number of enzymes, and some of those may have a protective role to play as well.
The simplest function of the seed coat is to actually act as a sort of coat, or, more specifically, a raincoat. In nature, a seed would rest in or on the soil through fall and winter, until spring rolls around and a new plant sprouts. If it sprouts prematurely, the infant plant will die because the growing conditions would be difficult or impossible. The seed coat keeps this from happening by providing a layer of waterproofing, which slows water absorption and discourages the seed from starting to grow.
A Colorful Coat...
The seed coat also contains a variety of pigments, which give the different kinds of corn their distinctive colors. Some of these are found on the pericarp and some on the aleurone layer that lies underneath it. Blue and red varieties get their color from pigments called anthocyanins, the same ones you'll see in red onions, blueberries and purple cabbages. They're known to be potent antioxidants. Yellow and orange hues come from carotenoids, just as they do in carrots. Your body can use those to make vitamin A. White corn lacks all of these pigments.
... Also Called the Bran
When switching from plant science to the culinary arts, the seed coat changes its name as well. Once you speak of it as food, the seed coat of the maize seed becomes the layer of bran around the kernel of corn. In this context, the bran is important for its nutritional role. Much of the corn's fiber is found in the bran and some of its oil as well. When you eat a whole-grain corn product, you get the added benefit of that fiber as well as the nutrients in the oil. Refined corn products don't always contain the bran.
The Germ of the Maize Seed
Digging more deeply into the maize seed, we come to the germ. You could think of this as as corn's equivalent of the egg yolk, because it's the part that actually grows into a new plant. That makes it the most important part of the maize seed, botanically speaking, and the seed coat and the endosperm are just there to protect it and nourish it along the way.
From the human culinary perspective, the germ is important as a source of oil, fiber and vitamins in the grain. As with the bran, any whole-grain corn product will include the germ as well. Not all do, because the oils in the germ can oxidize and become rancid over time. This reduces the shelf life of the product, so cornmeal and polenta and the like often are sold "degermed" to make them less perishable.
The Endosperm Is the Energy Reservoir
The last of the corn kernel's parts, the endosperm, could be thought of as the seed's "pantry" or its "gas tank," depending on your taste in metaphors. Either way, it's the main energy reservoir that the seed will rely on as it tries to grow into a new plant. As the germ begins to sprout, enzymes in the maize seed begin to digest the starchy endosperm and break its starch molecules down into simpler sugar molecules. Those provide the baby plant with the energy it needs to grow, until it produces its first few leaves and begins to make its own nutrients through photosynthesis.
It Feeds Humans, Too
The endosperm is also the most important part of the corn kernel from the human perspective. It provides most of the bulk of the kernel, and along with it comes most of the carbohydrates and calories. Those might be problematic for modern-day dieters, but for most of human history, our problem was getting enough calories to eat rather than fewer. The sugars in juicy, fresh sweet corn and the starches in dry, ground corn are the fuel that has powered entire civilizations.
Central and South America have lived for centuries on tamales, pupusas, tortillas and all their hundreds of regional cousins. The natives of New England made porridge with theirs, while white Colonists found any number of ways to make cornbread. Italians in many regions adopted polenta as a staple, as important in its way as pasta and risotto. Unfortunately, while the crop itself traveled widely, a key part of native wisdom didn't travel with it.
Bioavailability and Nixtamalization
If you're a modern American eating corn, know that it's part of a widely varied diet that contains a lot of other foods. If corn itself doesn't give you the nutrients you need, you'll get them from something else. That's not the case in cultures in which corn is the backbone of the diet.
This caused a problem when Europeans adopted corn in a big way, because a lot of the nutrients in corn aren't naturally bioavailable, which means that your body can't absorb them easily from the food. A disease called pellagra became a common complaint among poor people who couldn't afford to complement their corn with other foods.
In maize's homeland, indigenous peoples figured out pretty quickly that it was much more nutritious if it was soaked first in a strong solution of alkali, a process called nixtamalization. The seed coats soften and come off easily, and the tough, dried endosperm is softened and changed chemically. Its nutrients, especially B vitamins, are freed by the process and become digestible. New World cultures doubled down on nutrition as well by routinely pairing corn with beans, which added amino acids and other nutrients that maize simply couldn't provide.
Plain and Nixtamalized Corn Foods
In modern America, you'll find plenty of foods made with both natural and nixtamalized corn. Plain corn is what you see sold as cornmeal or polenta and in your cornmeal muffin mix. The corn in your breakfast cereal isn't usually nixtamalized either, because — like the milk you pour over it — cereal is enriched by adding vitamins to it directly. Sweet corn isn't nixtamalized either, whether you eat it fresh, frozen or canned.
Nixtamalized corn, with its distinctively different flavor, is sold whole as hominy or posole and ground as grits, masa or masa harina. It's also the form of corn you'll find in tortilla chips, tortillas, and the whole wonderful range of fried, baked and steamed masa products that make up the backbone of Latin cuisine.
- Whole Grains Council: Corn - October Grain of the Month
- Whole Grains Council: What's a Whole Grain? A Refined Grain?
- All Things Hominy: Eerything You Ever Needed to Know About Mixtamalization but Didn't Know to Ask
- Corn Journal: Archives
- Cook's Illustrated: Transforming Corn - The Science of Nixtamalization