Page 6 - Co Products Brochure

MAIZE WET-MILLING
Maize is an incredibly versatile grain. The end products of its processing are numerous,
and they are used in countless foods, beverages, drugs, cosmetics, industrial products,
as well as in animal feeds.
The first step in the processing of maize is “steeping”, which through softening the kernel,
facilitates the separation of the various components of the maize kernel.
Maize components:
Water constitutes about 12,6 percent of the maize kernel, with the balance
of the kernel (on a DM basis) being as follows:
Starch occurs in the endosperm of the grain in the form of granules and constitutes
about 70 percent of the kernel. It is a source of starches and nutritive sweeteners.
Most of the protein is found in the endosperm and is referred to as gluten. This
non-soluble protein is seperated from the starch slurry and is known as Gluten-60.
The husk is the fine skin around the kernel. The husks go into Gluten-20 for animal
feedstuffs.
The germ is the seed-like pod within the kernel. It contains about 50% oil and is a
source of oil for use in foodstuffs, drugs, and industrial products. Once most of the oil
has been removed, the remainder of the germ becomes maize germ cake meal and is
used in animal feed formulations.
The wet-milling process begins when maize is steeped in warm water and sulphur
dioxide to soften the kernels. The process is strictly controlled so that the bacterium
Lactobacillus
can reach an optimum level of lactic acid, which softens the maize by dis-
solving some of the protein and other binding material.
At the end of the steeping period, the excess liquid - corn steep liquor (CSL) - is separated
and concentrated by evaporation to a heavy liquid of approximately 40 percent solids.
The softened maize kernels are ground just enough to crack the kernel and free the
germ which still has some endosperm fragments (starch, gluten, and husks) clinging
to it. The germ is then separated from these fragments in hydrocyclones and dried to
a moisture content of approximately 4 percent.