Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/19/2005
Publication Date: 7/19/2005
Citation: Yang, P., Haken, A.E., Niu, Y., Chaney, S.R., Hicks, K.B., Eckhoff, S.R., Tumbleson, M.E., Singh, V. 2005. Effect of steeping with sulfite salts and adjunct acids on corn wet-milling yields and starch properties. Cereal Chemistry 82(4)p.420-424. Interpretive Summary: Steeping, the first step in the corn wet-milling process, is a time consuming, capital- and energy-intensive process. The conventional process requires the soaking of corn kernels in warm water containing sulfur dioxide and lactic acid. Sulfur dioxide is a toxic compound and many expensive steps must be taken to ensure there is no danger to human life during corn processing or from consumption of the final end products, starch, corn syrups, and corn oil. This study was conducted to see if different forms of sulfur in combination with different acids, both strong and weak, could be used in the wet milling process. It was hypothesized that if some forms of sulfur and acids were much more effective than the conventional process for steeping corn, then processors could use less sulfur and acids in the process, benefiting both economics and safety. It was determined that starch yields were affected by the type of sulfur compound and the type of acid used, but the effects varied for different corn hybrids. No major improvements in milling of corn could be discerned for these alternative steeping processes. Because of this result, efforts will be shifted to use of other processes, such as steeping kernels with enzymes, to improve the wet milling process.
Technical Abstract: Two corn hybrids (3394 and 33R87) were steeped with three sulfite salts and five acids to test the effect of sulfur dioxide (SO2)source and acid sources on wet-milling yields and starch properties. Milling yields from each treatment were compared with a control sample that was steeped with 2,000 ppm of SO2 (using sodiuim metabisulfite) and 0.55% lactic acid. Sulfur dioxide sources were potassium sulfite, sodium sulfite, and ammonium sulfite; acids were acetic, hydrochloric, oxalic, phosphoric, and sulfuric. Starch yields were affected by the SO2 source and steep acids but the effects were hybrid-dependent. Different steep acids gave different starch yields when wet milled at the same pH. Among the acids tested, weak acids (lactic and acetic) tended to give higher starch yields compared with strong acids (hydrochloric, sulfuric, phosphoric, and oxalic). Some differences were observed with different sulfite salts and acids on starch pasting properties; however, there were no clear trends.