Industrial corn processors currently use 20-25% of the yearly corn harvest to produce a number of products. For every five bushels sold, corn processors buy one bushel to process into sweeteners, starches, corn syrups, oils, ethanol, and animal feeds. These products then become the building blocks of thousands of other food and industrial products distributed throughout the world. Approximately 80% of corn grown in America is fed to poultry, livestock and fish. The nutritional components of yellow dent corn are well known. Components of Yellow Dent Corn
| Starch|| 61%|
| Corn Oil|| 4%|
| Protein|| 8%|
| Fiber|| 11%|
| Moisture|| 16%|
The 20% of field corn is transported from individual farms by truck or train to industrial corn processing plants. This percentage of industrial use versus the amount of corn produced has increased over the years. With the new bio-based product initiatives and our need for renewable energy, researchers are looking at corn as a feedstock for other organic chemicals and fibers. This will continue the trend of increasing percentage of corn grown for industrial processes. Educating nutritionists about the feeding values is becoming of increased importance.
There are two distinct ways for processing corn; wet-milling and dry-milling. Each process generates unique co-products. Corn Wet-Milling Process
Wet-milling processing roots are designed for production of pure starch. The corn wet-milling process seeks to extract optimum use and maximum value from each constituent of the kernel. In addition to starch and the other products, the industry has become an important source of specialized ingredients used in feed formulations.
Production of feed co-products from corn wet-milling begins with the delivery of shelled corn to the facility. The corn is sampled and quality approved. The corn is off loaded to elevator bins through a cleaning system. From the elevator, the corn is then conveyed to large tanks known as steep tanks where it is soaked for 30-50 hours in a diluted aqueous sulfur dioxide solution. This is a closely controlled process that results into the softening of the kernels. The water is later evaporated to concentrate the nutrients. The corn germ is then removed from the water soaked kernel. The germ is then processed to recover the corn oil. The remaining Germ Meal is extracted and cab be marketed for use as animal feed.
Following the removal of the germ, the rest of the corn kernel is screened to ensure removal of the bran, leaving the gluten protein and starch to be passed through the screens. The bran is combined with the concentrated, evaporated and dried steep water and other co-product streams. This produces Corn Gluten Feed. The gluten and starch slurry is then sent to centrifugal separators, which causes the gluten protein to float to the top as it's lighter and the heavier starch to sink to the bottom. The gluten protein is then dried and concentrated to form Corn Gluten Meal. Some of the starch is modified and dried and marketed to the food, textile and paper industries. The remainder of the starch can be processed into ethanol or sweeteners.
Wet-milling produces four major co-products for the feed industry from the isolated steep water, germ meal, bran and gluten. The co-products obtained are starch, gluten feed, gluten meal and corn oil.
The wet-milling process results in to yields of lower ethanol compared to a traditional dry-milling as some of the ferment-able starch are attached to the saleable co-products that exit the process. Corn Dry-Milling Process
This corn milling process is not as capital intensive as the wet milling process. It focuses on the major production of ethanol, among other products. In this process, the corn is cleaned of foreign materials and hammer milled to a medium-course to fine grind meal. The corn meal is then mixed with fresh and recycled water in known ratios to form slurry which is then used in the process of ethanol production.
Dry corn millers process corn in one of the following three ways;
- Stone-ground or nondegerming process
- A tempering degerming process
- Alkaline-cooked process
Each miller has his or her own unique variations on the overall processing system. The major products from dry-milling are ethanol, dried distillers grains, and carbon dioxide.
The corn plant has proven to be a very versatile grain. The end products produced from corn milling are used in our everyday life. Despite the high amount of capital required for wet-milling process, its capability to produce a wide variety of co-products is viable in the markets today.