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The magical process of corn wet grinding: how to turn an ordinary corn into a variety of precious products?
Wet milling of corn is a unique process that breaks down corn kernels into their components, including corn oil, protein, cornstarch, and fiber. The process uses water and multiple steps to separate corn's building blocks, transforming it into a variety of value-rich products, primarily for the food industry.
The corn wet grinding industry has become an important part of the American manufacturing industry and has a long history. Corn refiners have established this process since more than 150 years ago, focusing on breaking down corn kernels into their four main components that can be used.
Historical background
The history of the corn wet grinding industry in the United States can be traced back to the 19th century. Corn refiners formed the Corn Products Manufacturers Association in 1913. As the corn refining industry developed, the industry provided a diverse range of products, and the corn wet grinding process became its foundation. The four main components of this process --- oil, protein, starch and fiber --- are the main products of corn wet grinding.
Process description
Wet milling of corn is a physical separation process, mainly based on differences in weight and size. The process is characterized by the need for water as a separation or carrier agent. Most of the products are of high value and require wide application in the food industry. This process bears witness to the value of every part of the corn.
Process Steps
Cleaning
According to the standards of the United States Department of Agriculture, corn wet grinding usually uses grade 5 corn. Harvested corn must first be washed using a suitable sieve to remove unwanted impurities such as corn stalks, foreign seeds, metal, leaves and dust.
Soak
During this process, the plant is hydrated in water to loosen the starch granules and preserve the toughness of the grain germ. The addition of sulfur dioxide and lactic acid helps destroy the protein matrix of the endosperm, facilitates the separation of starch, and prevents the growth of microorganisms. The soaking process usually takes about 40 hours, after which concentrated soaking water is obtained. This by-product can be used for other purposes such as animal feed.
Germ recovery
The germ is separated to remove the oil from the corn to ensure that it does not contaminate the final product. In this process, a low-speed mill is used to coarsely grind the softened corn into a thick paste-like mixture. After the water is added and diverted, the germ will float out, and then the oil can be extracted multiple times.
Fiber recycling
The main components of the downstream stream obtained after water circulation are fiber, protein and starch, which will then be screened through multiple grinders and screens. Separating the fibers according to their size produces corn bran that is rich in protein and can be used as an ingredient in animal feed and human consumption.
Protein recovery
The slurry in this step is called corn steep liquor and contains protein and starch. After the water is removed, it is run through a centrifuge to separate the starch and gluten. The separated starch stream is widely used in the food industry due to its high purity.
Starch treatment
Starch requires multi-stage cleaning to ensure its high purity recovery. This process recycles water and ensures high purity of the starch for final applications.
Manufacturing of by-products
During the wet grinding process, about 34% of the output comes from by-products. These by-products are not only used to make animal feed but also contribute to the needs of other industries. Although it has "gluten" in the name, it doesn't actually contain any gluten protein.
Main products
The main products of the corn wet milling process include soaked water solids, germ, fiber, starch and gluten. These products can be further processed to form high value-added products.
Research Prospects
Researchers are constantly looking for ways to improve the efficiency of the corn wet grinding process. With the development of technology, new methods are constantly emerging, such as shortening the soaking time by adding enzymes.
In this process, it is worth thinking about: How will the efficient use of these resources affect our future diet and environment?
