Corn (maize): classification, quality and applications / Articles

Corn (maize, Zea mays) is an annual herbaceous plant of the grass family, whose grain is one of the most versatile and in-demand agricultural crops in the world. In terms of global production, corn is second only to wheat and rice, but in breadth of application it has no equal: it is used for food production, starch, syrup, glucose, oil, alcohol, biofuel, and is the main component of compound feeds for animals and poultry. Due to its high yield and adaptability, corn is cultivated on almost all continents, from the tropics to temperate latitudes.

Chemical Nature and Grain Composition

Corn grain is distinguished by a high content of carbohydrates and fat. The chemical composition (in % on a dry basis) varies depending on the type and variety: starch — 65–75%, protein — 8–12%, fat — 4–6% (in the germ up to 30–40%), fibre — 2–3%, ash — 1.5–2%. The corn germ, which accounts for about 10–12% of the grain weight, is a valuable source of edible corn oil rich in unsaturated fatty acids, vitamin E and phytosterols. Corn proteins are represented mainly by zein, which is poor in lysine and tryptophan, which is taken into account when balancing feed rations. Corn also contains B vitamins, carotenoids and minerals.

Classification, Types and Classes

In Russia and CIS countries, requirements for corn during harvesting and supply are established by GOST 13634-90. Depending on the colour and shape of the grain, corn is divided into several types:

Type I — dent yellow (yellow, orange, with a white tip).
Type II — dent white (white, pale, pale pink).
Type III — flint yellow.
Type IV — flint white.
Type V — semi-dent yellow.
Type VI — semi-dent white.
Type VII — popcorn white (for popcorn production).
Type VIII — popcorn yellow.
Type IX — waxy (with a high content of amylopectin).

Corn containing an admixture of grains of other types in excess of the established norms is defined as a "mixture of types" with an indication of the type composition in percent.

By quality, corn is divided into three classes. Corn of classes 1 and 2 is intended for food purposes, and class 3 — for feed purposes and for the production of compound feeds. Basic quality norms for food corn: moisture — not more than 15.0%, foreign matter — not more than 2.0%, grain impurities — not more than 7.0%. For corn supplied for processing, additional requirements apply depending on the direction of use: for the groats industry — types III, IV, VI; for the food concentrate industry — types I–V, VII and VIII; for the starch industry — types I, II, V and VI.

For feed corn, a separate standard applies — GOST R 53903-2010 "Feed corn. Specifications", which establishes norms for moisture, test weight, foreign and grain impurities, as well as safety indicators.

Key Quality Indicators

Corn quality is assessed by a set of physicochemical indicators. Test weight (bulk density) for food corn must be at least 650–670 g/L depending on the class. Moisture — not more than 14–15% (for long-term storage). Foreign matter — not more than 2%, grain impurities — not more than 7%. The content of toxic elements, mycotoxins (aflatoxins, fumonisins), pesticides and pest infestation are mandatory controlled. For the starch industry, starch content and extractability are important.

Production and Processing Technology

Corn cultivation includes soil preparation, sowing, care and harvesting. Depending on the intended use, harvesting is carried out at the stage of full grain maturity (for grain purposes) or at the stage of waxy maturity (for silage and corn cob mix). After harvesting, the grain is cleaned, dried and sorted. The main processing directions are:

Starch and syrup production: production of corn starch (corn accounts for about 75% of world starch production), syrup, glucose, maltose syrups, gluten and corn oil.
Food production: corn groats, flour, flakes, canned corn (kernels and cobs), popcorn, corn oil.
Feed production: corn (in grain, silage and corn cob mix) serves as the main energy component of compound feeds for pigs, poultry and cattle.
Industrial processing: production of ethanol (bioethanol), alcohol, organic acids and bioplastics.

Applications

Food consumption. Corn is used for the production of groats, flour, flakes, corn oil, starch and glucose-fructose syrups. These products are widely used in baking, confectionery, canning and the beverage industry.

Starch and deep processing. Corn starch and syrup are raw materials for the confectionery, pharmaceutical, textile and paper industries. Gluten is used in feed production and as a food ingredient.

Feed production. Corn in grain, silage and corn cob mix is a key energy feed for animals. Silage is made from whole plants at the waxy maturity stage, and corn cob mix — from grain-cob mass.

Industrial purposes. Corn serves as a raw material for the production of bioethanol, alcohol and bioplastics, making it an important element of renewable energy and sustainable chemistry.

Safety and Storage

Corn is a combustible material, but the main risk during storage is associated with biological processes. Grain is hygroscopic: at moisture above 14–15%, respiration, mould growth and mycotoxin accumulation are activated. Storage is carried out in dry, well-ventilated grain stores (elevators, flat stores) at controlled temperature and humidity. Regular monitoring of pest infestation (granary weevil, mites) and active ventilation must be ensured. When working with grain dust, respirators are recommended.

Market and Trends

The global corn market is the largest among grain crops. According to USDA estimates, global corn production in the 2025/26 marketing year is about 1,295.9 million tonnes, and global consumption is a record 1,301.3 million tonnes. Global exports are estimated at about 206 million tonnes. The largest producers are the USA (about 425.5 million tonnes), Brazil (about 131 million tonnes), China, Argentina (about 53 million tonnes) and Ukraine. Russia is also increasing production and exports: in 2026, corn yield rose to 70 c/ha, and exports in the first half of 2026 exceeded 2.6 million tonnes (2.7 times more than a year earlier). The main destinations for Russian exports are Vietnam, the Philippines, China and the Middle East.

Key industry trends include growing demand for corn for deep processing (starch, syrup, gluten, bioethanol), the development of silage and corn cob mix production for livestock, and the expansion of exports to the Asia-Pacific region. Producers with access to quality grain and modern deep-processing capacities occupy stable competitive positions.

Conclusion

Corn remains a strategically important versatile crop of global agriculture and the food industry. Understanding the classification according to GOST 13634-90, the differences between types (dent, flint, popcorn, waxy), classes (1–3) and key quality indicators (test weight, moisture, impurities) is the basis for competent selection of grain for specific purposes — from starch and syrup production to feed production and export. Organising corn supplies, including the selection of types and classes, requires an individual approach.