Corn Milling 101 Part 3: Cleaning, Cracking & Sifting

The first step in corn processing is cleaning. We remove any cobs or stalks and sort out broken kernels using a screener and separator. Then the corn goes through a magnet to pull out any remaining foreign material. When the cleaning process is finished, the whole corn kernels should be all that’s left.

The clean, whole kernel corn is then sent to the tempering system to loosen the skin, otherwise known as bran or pericarp. A small amount of water is added to the corn and then it sits in a holding tank for a period of time.

After the skin has been loosened, the corn goes to Didion’s degermination system. The corn is cracked into large pieces. During this process, the loose skin comes off the kernel and the germ pops out. For more information on the parts of the corn kernel, check out Milling 101 Part 2: Where Our Food and Fuel Products Come From.

The fractionated pieces are sifted to sort out any fine, floury materials. These soft, starchy pieces are sent to our ethanol plant because they are optimal for fermentation. For more information on how we maximize every kernel of corn through the partnership between our dry corn mill and ethanol plant, check out Milling 101 Part 1: A Fresh Look at Corn Milling.

Next, the bran is removed using an aspiration system. Then it is transferred to its own system within the mill. The remaining starch goes through a series of grinding and sifting. Pieces are sorted using wire screens of various sizes to separate “unders” or “fines” from the “overs” and “select” pieces. These terms refer to where the pieces sit on the wire screens during sifting.

The fines go to the ethanol plant for fermentation while the overs and select pieces are used to make food products in the dry corn mill. Our millers prefer the select size pieces, which is a nice center cut of the kernel. These “center cut” pieces are made from the hard starch. This enables our millers to make a very consistent finished product for customers and product consumers. This is part of the Didion Difference.

By: Curt Miller, Corn Milling Operations Manager at Didion Milling