The present research evaluated the feasibility of using ozone (O 3) to replace sulfur dioxide (SO2) in corn steeping. Traditionally, steep water contains 0.1-0.2% sulfur dioxide to promote starch-protein separation and high starch yields, and to control microbial growth. However, residual SO2 in starch products affects product quality and jeopardizes the "organic products" claims. Also, SO 2 discharged to the environment pollutes water and air. Ozone is a strong oxidant and disinfectant with a capability to control the growth of putrefactive microorganisms in steeping systems, and to break down the endosperm protein matrix and, hence, improve starch release. This study demonstrates that an ozone-aided steeping (OAS) process had starch yields as high as conventional SO2 steeping. OAS processes can be conducted at a lower temperature (20°C vs. 50°C) and for shorter times (36 hr vs. 48 hr) than the conventional SO2 processes, suggesting significant energy savings and increased productivity. We have found that the timing of ozone application is of great importance to the performance of the OAS process.