Production Process Of Corn Steep Liquor Powder

- Feb 23, 2019-

Corn steep liquor is a byproduct of the initial stages of wet milling of corn. Steeping of corn

(i.e., soaking in water) aids in the separation the various components of corn such as starch and

nutrients. Corn is normally steeped in stainless steel drums holding from 3,000-25,000 bushels

of corn (CRA 2002; White and Johnson 2003). Approximately 5-9 gallons of water per bushel

of corn is added to the tank (Liggett and Koffler 1948; White and Johnson 2003). The water

originates elsewhere in the wet milling process where it has already obtained some soluble corn

matter. The temperature of the water is maintained at 45-54˚C by heating the water as it is

recirculated or by using a heat exchanger (Liggett and Koffler 1948; CRA 2006a; White and

Johnson 2003). Immediately before adding the water to drums, an aqueous source of sodium

dioxide is added to the water to a concentration of 0.1-0.2% (Liggett and Koffler 1948; White

and Johnson 2003). In water, these sources of sodium dioxide form sulfurous acid, which

controls fermentation and softens the corn kernel to aid in the separation of the corn products.

Most of the sulfurous acid is absorbed by the corn kernels so that after ten hours the

concentration of sulfurous acid in the steepwater is lowered to 0.01% (Liggett and Koffler 1948).

The corn is steeped for anywhere between 22-50 hours, while the CSL is moved through six to

twelve successive steeping tanks. The CSL is initially added to the tank with the oldest corn so

that it is in contact with the highest concentration of the sulfurous acid. The water is then moved

to fresher corn so that the oldest CSL is in contact with the freshest corn. Approximately one-

third of the water is absorbed by the corn during the steeping, and the other two-thirds is

withdrawn from the steeping system as light steepwater that contains between 6-9% solids by

weight. The light steepwater is then evaporated until it contains 40-60% solids. The resulting

CSL may be further processed by downstream users to meet their own specifications (White and

Johnson 2003; Budavari 1996).