Types and Structures of Corn/Maize

Corn (also called maize) is native to central and south America, but now it’s cultivated all around the world and has become one of the three most important food crops in the world along with wheat and rice.

1. Classification of corn and its characteristics

Corn can be classified into yellow corn and white corn. Yellow corn refers to those with yellow bran and also includes reddish corn while white corn has white bran and sometimes with yellowish or pinkish bran. Based on the grain shape, hardness and application, corn can also be classified into dent corn and flint corn. Dent corn has horse tooth shaped grain with cutin at both sides of the endosperm and its middle and top are all farinaceous. As for flint corn, its grain is normally in round or short square shape with endosperm surrounded by cutin.

2. Structure of corn grain

Corn grain consists of bran, endosperm, germ and root cap.

• Bran(Pericarp)

Corn bran is composed of outer bran and aleurone layer.

The outer bran has a high content of crude fiber and is quite tenacious and hard to break. But once it’s moistened, it’s easy to be removed. Aleurone layer is located in between the outer bran and endosperm and has high nutrient content.

• Endosperm

Endosperm is the largest component of corn grain and can be divided into two types: cutin endosperm and farinaceous endosperm. Cutin endosperm is featured with compact structure, great hardness and transparent and shiny appearance. It’s not easily broken during bran removal and therefore suitable for making corn grits. On the contrary, farinaceous endosperm is incompact in structure and has small hardness, thus it’s easily broken during bran removal and thus fit for making corn flour.

• Germ

Germ is located at the base of the corn. Being tenacious and elastic, it’s not easy to break and can be extracted entirely from the grain during processing. The fat content reaches up to 35%~40%.

• root cap(Scutellum,Hypocotyl,Radicle)

Root cap situates at the bottom and only forms 0.8%~1.1% of the grain dry weight. It should be removed during processing.

• Mass ratio of various components of corn