Sulfur Dioxide-Supplemented Ambient Air Drying of High-Moisture Corn
AMBIENT air grain drying in the Corn Belt has been hampered by climatic conditions that yield a rate of drying too slow to prevent grain deterioration. Rather than attempting to increase the drying rate through sup­ plemental energy or increased air flow, an investigation was made to determine the feasibility of using sulfur dioxide gas as a microbial growth inhibitor to extend the time for safely drying with ambient air. In laboratory tests, 25 percent moisture corn was treated with various concentrations of sulfur dioxide (0.01 to 1.82 percent wt S02/wt corn). Under conditions ideal for mold growth, corn treated with 0.4 percent or more S02 withstood microbial deterioration for several weeks. In field tests, application of sulfur dioxide reduced the initial microbial population in freshly harvested corn. Subsequent intermittent applications of sulfur dioxide maintained low microbial counts until ambient air dry­ ing was completed. High microbial counts were present in a control bin throughout drying, and visible quality deterioration due to this microbial activity was observed. No detrimental decrease in corn quality was evident from the use of the "trickle-S02" process as measured by of­ ficial grading of the corn, fatty acid analysis, thiamine analysis, and corn dry milling results. The results of this research are presented for the pur­ pose of providing information on the potential use of sulfur dioxide and do not imply endorsement or authori­ zation for this use by USDA.