How Corn Starch Is Made: Manufacturing Process and Starch Extraction Technology
libre
Corn starch is obtained by completely extracting the starch granules from the cells of the plant tissue in which they are locked. Because those granules are bound inside the cell structure, freeing them is a fairly involved process that relies on soaking, milling, separation and purification. The recipe for corn starch below walks through each stage. 
How is corn starch produced?
Corn starch production begins by steeping the kernels in warm water that contains about a quarter of one percent sulfurous acid. The sulfurous acid softens the kernel and, just as importantly, it suppresses the growth of unwanted microorganisms during the soak.
During steeping, part of the protein matter and salts pass into the solution. The corn steep liquor produced this way has considerable value as animal feed. After soaking, the kernel is crushed so that the germ separates from the endosperm.
The germ is separated from the crushed mass by exploiting differences in specific gravity. Because the germ contains a large amount of fat, it is lighter than the rest of the kernel, which makes it possible to float it off from the broken grain. Once the germ has been removed, the coarse meal — the grits — is finely ground in a milling step that completes the release of starch from the plant cells.
What is starch milk and how is it separated?
The next group of operations is concerned with separating the starch milk, that is, a suspension of starch and impurities in water. These operations are carried out on sieve equipment and are referred to collectively by the term sieving.
Starch milk is then purified, or, as the trade puts it, refined. Refined starch milk contains from 11 to 14% dry matter. Starch makes up the bulk of that dry matter, between 80 and 92%. The starch milk also carries 6–10% protein substances, along with a small amount of fat, mineral salts and other impurities.
How is the starch freed from protein and impurities?
The remaining task is to free the starch as completely as possible from protein and the other impurities, and this is achieved by washing and filtration. The purified raw starch is then dried down to a moisture content of 13%. When processing corn kernels into starch, the yield ranges from 60 to 66% calculated on anhydrous corn.
Of the total amount of starch contained in the kernel, between 86 and 93.5% is extracted. It is worth noting that starch production uses predominantly starchy varieties of corn as raw material.
Such varieties hold more starch and less of the protein matter that hinders the separation and purification of the starch. Starch is also produced from dent and semi-dent corn.
