Effect of steeping with sulfite salts and adjunct acids on corn wet-milling yields and starch properties

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 sodium 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.