OMRI Position on Corn Steep Liquor

(January 13, 2011) In order to clarify our position on Corn Steep Liquor (CSL) as an ingredient, and so that organic stakeholders know where OMRI stands, we are reposting the lead article from our Spring 2010 Material Review Newsletter. The article describes OMRI’s position regarding CSL, and explains how we arrived at this determination. Until further notice, we will continue to follow the NOP directive and treat CSL as an allowed nonsynthetic ingredient for the purpose of product review.

Corn Steep Liquor

By Lindsay Fernandez-Salvador, OMRI Review Program Manager

Corn steep liquor (aka condensed fermented corn extractives) is a by-product of the corn wet milling process. According to the Corn Refiners Association, “CSL is a viscous liquid mixture consisting entirely of water-soluble components of corn steeped in water” (Corn Refiners Association, 2008 [1]) . Since the corn kernel is a complex mixture of starch, protein, oil, water, fiber, minerals and vitamins, the corn wet milling process yields many widely used products such as corn oil, corn germ meal, cornstarch, and high fructose corn syrup. Corn is soaked, or “steeped” in 120°F to 130°F water containing 0.1%-0.2% sulfur dioxide for 24-48 hours. The sulfurous acid formed induces chemical and physical changes in the kernel, in effect separating the starch and insoluble protein by cleaving protein disulfide cross-links in the endosperm protein matrix. (Dailey, 2000) The sulfurous acid also helps to control undesirable microorganisms, and allows dissolved sugars to be converted to lactic acid, which helps to maintain a pH near 4.0. During the steeping process, about 6% of the dry weight is dissolved, which is then evaporated to condense the steepwater into corn steep liquor.(Corn Products International, 2009) The remaining insoluble corn kernel is then further processed to produce many products used in foods, livestock feeds, and fertilizers.

In the past, OMRI had reviewed CSL and determined it to be nonsynthetic. However, the NOSB’s 2006 refinement of the definitions for synthetic vs. nonsynthetic substances caused us to revisit that decision to determine whether CSL can still be considered nonsynthetic. For technical questions such as these, OMRI relies on our Advisory Council, an independent body made up of experts in their fields, to vote on issues such as the status of a substance. The Advisory Council Crops Committee (ACCC) was provided with peer-reviewed literature, patents, manufacturing processes, and a copy of the 2006 NOSB synthetic/nonsynthetic decision tree catered to CSL to help inform their votes. In May 2009, the ACCC voted 8-2 that corn steep liquor is synthetic. Later, OMRI received additional information that lent to the argument that it was not synthetic; mainly that lactic acid is the driving force for the chemical change rather than sulfurous acid. Lactic acid is produced naturally in the steeping process through the conversion of dissolved sugars. The ACCC was asked to vote again, taking into account the new information. Again, the council voted that CSL was synthetic, 7-3. This comment from an Advisory Council member summarizes the prevailing argument: “As long as any of the active species [Sulfurous acid] is present, it can react with the proteins. Breaking of disulfide bonds is an irreversible reaction that goes to completion. Once the sulfite ion reacts, more of it is produced by the ionization process to maintain equilibrium conditions. The suboptimal pH of the industrial process does not stop breaking of disulfide bonds by sulfite ion. It only slows it down. In the industrial process some of the bonds are probably broken by lactic acid, but it is unreasonable to assume that the entire degradation process is due to unilateral action of lactic acid produced in the fermentation reaction.”

In a memo on November 12, 2009, the NOP asked the organic industry to consider CSL nonsynthetic and allowed for use in organic agriculture until the National Organic Standards Board (NOSB) could discuss it at its Spring 2010 meeting. The NOSB did discuss CSL at both its Spring and Fall 2010 meetings. In fact, there was significant public comment on the classification of CSL at the Fall meeting, supporting both the NOSB Crops Committee’s majority and minority opinions. OMRI commented that for classification purposes, the NOSB should first focus on the manufacturing process of CSL and whether it led to chemical change. The Crops Committee voted to table the vote until the April 2011 NOSB meeting so they could review new material. CSL will continue to be allowed for use in organic production in the meantime.

Although our Advisory Council voted twice that CSL is synthetic, OMRI has followed the NOP directive and currently lists products with CSL. We have provided OMRI’s research and discussion materials (with confidential information redacted), at the National Organic Program’s request, for consideration by the NOSB.           

Ethanol Production Flowchart

[1] Assessment Plan for Corn Steep Liquor (CAS#66071-94-1) in Accordance with USEPA High Production Volume Chemical Challenge Program. 2006. Prepared for The Corn refiners Association by Keller and Heckman LLP. Retrieved from

This article was originally published in the Spring 2010 OMRI Materials Review newsletter and was updated in January 2011.