Mycoflora of high-moisture maize treated with ozone

Abstract

This study evaluated the effectiveness of ozone to reduce the presence of fungi in stored high-moisture maize. Maize at moisture contents of 18, 22 and 26% (wet basis) were treated with air having ozone concentrations of 0, 50, 500, 1000 and 15,000 ppm for 1 h at a flow rate of 0.5 L min−1. After treatment, maize samples were surface disinfected and fungal species – Aspergillus, Cladosporium, Curvularia, Fusarium, Mucor, Penicillium, and Rhizopus – enumerated in the samples. The response to grain moisture content varied with fungal species. The average fungal infections per 100 kernels of maize for the non-ozone treated samples was 14.0 for Aspergillus, 0.6 for Cladosporium, 0.9 for Curvularia, 28.6 for Fusarium, 11.6 for Mucor, 56.9 for Penicillium, and 3.2 for Rhizopus. Ozone at the median concentrations – 500 and 1000 ppm – was most effective in reducing the presence of Aspergillus (p < 0.0001), Fusarium (p < 0.0001) and Mucor (p < 0.0001). Penicillium infections decreased with ozone concentrations of 1000 and 15,000 ppm (p < 0.0001). An ozone concentration of 15,000 ppm was necessary to reduce Rhizopus infection (p < 0.001). Ozone is capable of penetrating the surface of maize kernels to reduce fungal infections during storage. Ozonation of high-moisture maize is likely most effective in controlling the activity of Aspergillus and Fusarium due to their relatively high occurrence of infection on non-ozone treated maize and the observed reduction in their presence at lower ozone treatment concentrations.