Maize Grain

Traded maize is dent or flint field maize, shelled and dried. Kernel type matters commercially: dent maize, with its soft starch core, dominates bulk feed and wet-milling trade, while harder flint types behave differently in dry milling and resist storage insect damage better. Colour is also a trade descriptor — yellow maize dominates the international feed trade, while white maize carries a distinct food market and is priced separately where it is a staple.

Maize supports more distinct processing routes than any other cereal. Dry milling separates the kernel into endosperm fractions — grits, meal, and flour — plus germ and bran; cornmeal is the primary food output of that route, while the germ is recovered as a valuable oil-bearing co-product and the bran leaves as a residual feed stream. Wet milling instead steeps the kernel to extract starch, yielding starch, sweeteners, gluten feed, and gluten meal. A large share of the crop bypasses milling entirely and is fed whole or ground, and in several countries a further large share is fermented to fuel ethanol.

• Feed — fed whole, cracked, or ground, and as the energy base of compound feeds
• Food — dry-milled into meal, grits, and flour; nixtamalised for tortillas and masa
• Industrial — wet-milled for starch and sweeteners; fermented for ethanol
• Energy — fuel ethanol feedstock, with distillers grains returning to feed
• Seed — hybrid seed production, a separate identity-preserved trade

The product pathways modelled here cover the dry-milling route. Wet-milling outputs and distillers grains are real and commercially large, but they are separate processing chains and are not asserted as products of this commodity page until they are described in their own right.

Maize grades on moisture, test weight, total damaged kernels including heat damage, and the combined category of broken corn and foreign material. That last measure is unusually important for maize: the kernel is large and the germ sits exposed at one end, so shelling, augering, and drop-handling all generate fines and broken pieces. Broken material stores worse than whole grain, concentrates in the centre of a bin, and impedes aeration, so the physical condition of a lot has direct consequences for how long it can be held.

Maize is also the cereal most consistently associated with mycotoxin risk. Fungi in the Aspergillus and Fusarium genera can colonise the grain both in the field and in store and can produce toxins including aflatoxins and fumonisins. Regulatory limits for these exist in most jurisdictions, apply to the lot rather than to the crop, and are enforced independently of the commercial grade — a lot can meet its grade and still be rejected on a mycotoxin result.

In temperate production maize is routinely combined above safe storage moisture and dried mechanically, which makes the grain dryer part of the commodity chain rather than an optional refinement. Drying too fast or too hot induces stress cracks in the endosperm; cracked kernels break more readily in later handling and lose value in dry and wet milling alike. In warm climates the pressure runs the other way — the window between harvest moisture and mould growth is short, and hermetic or well-managed conventional storage is what protects the lot.

Once dry, maize moves in bulk by truck, rail, barge, and vessel in very large volumes, and stores in everything from on-farm bins to port terminals. Because broken material and fines drive both storage risk and grade, cleaning before storage and careful handling at every transfer point repay themselves across the chain.