Corn Kernel Anatomy: Structure, Parts, and Composition of Corn Grain
libre
A corn ear consists of a core (commonly called the cob in everyday speech) and the kernels attached to that core, regardless of which type or variety the corn belongs to. At the natural moisture level of the ear, the core makes up 16 to 25% of the total weight, while the kernels account for 75–84%. Most often the kernels represent 77–79% of the ear's weight.
The number of kernels on an ear depends on the type and variety of corn. Some corn varieties produce ears bearing 1,000 or more kernels.
A corn kernel is, above all, a seed from which a new plant is meant to grow in the future. For this reason, deep inside every kernel there is a tiny sprout — the embryo — waiting for its time. 
That food is stored within the kernel itself, which acts as a tiny pantry where nature has carefully laid in the nutrients the embryo will need. These substances are securely hidden, because on the outside the kernel is covered by several layers of coats made of coarse, woody cells.
Beneath the coats lies the so-called aleurone layer of cells, and only behind it is the kernel's main "treasure" — the inner, floury part known as the endosperm.
What is the anatomical structure of a corn kernel?
A corn kernel consists of four main parts. Looking at its anatomical structure, these can be listed as:
- the embryo (germ);
- the endosperm;
- the coats;
- the aleurone layer.
Longitudinal section of corn kernels of various botanical varieties
The coats — what is usually called the hull — come in two kinds: fruit coats and seed coats. In addition, one more part of the kernel is sometimes distinguished, making up just 1–1.5% of the weight: the tip cap, or base. It is by this tip cap that the kernel is attached to the core of the ear.
The endosperm makes up 70 to 78% of the entire kernel's weight. It is rich in starch, while its outer layers contain proteins. Popcorn, flint, and dent corn differ from other varieties in having a hard, horny endosperm; the kernels of these types contain somewhat more protein. Floury corn, by contrast, has no horny layer at all. If you cut open such a kernel, you see a uniform, mealy mass.
The corn embryo occupies a large place in the kernel; its weight equals 8 to 15% (on average 10–12%) of the entire kernel. The embryo is rich in proteins and mineral salts. Moreover, it is nearly half fat and contains a significant amount of vitamin E (tocopherol).
This is understandable, since it is precisely the embryo that is destined to give life to a new plant. That is why the most valuable, biologically active substances are concentrated in it.
The coats make up 7–9% of the kernel's weight, and the aleurone layer 6–8%. The coats consist mainly of indigestible fiber (cellulose); they also contain a significant amount of mineral salts and all the coloring substances (pigments) that determine the color of the kernels.
By color the kernels are predominantly white and yellow, but kernels of red, brown, blue, violet, and even black also occur. Corn kernels also differ from one another in size and weight.
The weight of 1,000 corn kernels varies within fairly wide limits: from 50 to 1,100 g. Most often, however, the weight of 1,000 kernels is 200–300 g, meaning the weight of a single kernel averages 0.2–0.3 g. We have described what each part of the corn kernel contains and what it is rich in.
And what is the chemical composition of the kernel as a whole? Read about the mineral substances in the composition of corn in the next article.
