Efficacy of fixed bed ozonation treatment to control insects in stored bulk grain

Abstract

Scale-up demonstration trials were conducted at the pilot bin facility of the Purdue University Post-Harvest Education and Research Center in June 2005, August 2006, July 2007, and October 2008 with conventional yellow maize and at a popcorn storage facility in July 2005 and 2006. The primary objective of these trials was to determine the efficacy of ozonation to control insect pests without affecting end-use quality. The setup consisted of generating ozone at a constant rate with commercially available generators, introduction in the headspace, drawdown to the plenum with a fan with a minimum air velocity through the grain of 0.03 m/s, re-circulation back into the headspace or exhausting from the plenum into another bin. Ozonation was done to attain an ozone concentration of 50 ppm in the plenum to be maintained for a period of 72 h (3,600 ppm-h). When this concentration was not achieved, an ozone concentration-time product of 3,600 ppm-h was aimed for extending the time to expose the grain mass to the same treatment effect to achieve 100% insect mortality. The trials were performed using insect bioassays with adults of maize weevil (MW) and red flour beetle (RFB). Insect mortality was essentially 100% for both MW and RFB. The concept of two phases of ozonation and the airflow rates needed to achieve the required treatment levels of 3,600 ppm-h were investigated. The trials at the popcorn facility confirmed that end-use parameters of popcorn were not affected.