Publication no. C-1999-0726-02R |  VIEW ARTICLE

Batch Steeping of Corn: Effects of Adding Lactic Acid and Sulfur Dioxide at Different Times on Starch Yields, Protein Contents, and Starch Pasting Properties (1).

V. Singh (2,3), A. E. Haken (2), M. K. Dowd (4), Y. X. Niu (2), S. H. Zou (2), and S. R. Eckhoff (2). (1) Mention of product or trade name does not imply endorsement by the University of Illinois. (2) Visiting assistant professor, research specialists, research technician, and professor, respectively, Department of Agricultural Engineering, University of Illinois, Urbana, IL 61801. (3) Corresponding author. E-mail: <vsingh@arserrc.gov> Current address: USDA/ARS/ERRC, 600 E. Mermaid Lane, Wyndmoor, PA 19454. (4) Chemical Engineer, USDA-ARS-SRRC, New Orleans, LA. Cereal Chem. 76(5):600-605. Accepted April 27, 1999. Copyright 1999 American Association of Cereal Chemists, Inc.

The effect of adding lactic acid and sulfur dioxide at different times from the start of batch steeping on corn starch yields was studied. Five commercial hybrids were steeped with 0.5% lactic acid or 0.2% sulfur dioxide added over the first 15 hr of steeping and wet-milled following a 100-g corn wet-milling procedure. No significant differences were observed in starch yields when lactic acid was added to the steep solution (SO(2) and water) from 0 hr (start of steeping) to 15 hr. Addition of SO(2) to the steep solution (lactic acid and water) resulted in significantly higher average starch yields when SO(2) was added between 5 and 15 hr compared with addition at 0 hr (SO(2) and lactic acid for full 24 hr of steeping). Based on the results of the first experiment, a second experiment was done in which one of five original hybrids was steeped for 24 hr, during which lactic acid or SO(2) was added until 23.9 hr (i.e., 5 min before milling) after the start of steeping. Similar results were found in the second experiment. Residual protein in starch samples did not exceed 0.85%. Steepwater protein content decreased with delays (16-20 hr) in adding either chemical to the steep solution. A significant effect on starch pasting properties of chemicals and duration of chemicals in steepwater was observed. Testing these findings using a larger scale (1,000 g) corn wet-milling procedure produced results similar to those obtained with the 100-g corn wet-milling procedure.