Ozone Treatment of Cereal Grains: Fungal Control and Grain Germination Implications

Cereal grains are fundamental to global food security and agriculture. However, these grains face significant challenges throughout the production chain, particularly from fungal contamination, which leads to substantial economic losses, degradation of grain quality, and potential health risks due to mycotoxins. Traditional methods for controlling fungal contamination, such as the use of synthetic fungicides, face limitations including fungal resistance, environmental concerns, and potential health risks. As a result, there is a growing need for more sustainable and effective solutions.

This PhD thesis explores the potential of ozone as an alternative method to conventional synthetic fungicides for reducing fungal contamination in cereal grains while preserving their germination capacity. Ozone is a powerful oxidizing agent with broad-spectrum antimicrobial activity that breaks down into oxygen, minimizing health risks and environmental impact. The research investigates the effects of ozone on fungi, including key mycotoxigenic species such as Fusarium and Penicillium, as well as other fungi relevant in the organic industry, like Tilletia. The study also examines how ozone influences seed germination, balancing its antimicrobial

benefits with potential impacts on grain viability. Additionally, it explores critical factors affecting ozone's efficacy, including concentration, exposure time, grain moisture content, relative humidity, and temperature. The study aims to establish dose thresholds, ensure grain stability during storage, and identify optimal post-harvest treatment conditions, with significant implications for industrial applications. The inclusion of multiple cereals enhances the relevance of this research for worldwide agriculture, as it could provide a broad-spectrum solution for reducing fungal contamination across diverse crops, improving food security and sustainability on a global scale.

The thesis is structured around three primary studies. Paper I focuses on malting barley, examining the effects of ozone on Fusarium spp. contamination, various factors affecting ozone efficacy, and grain stability during storage. Paper II assesses the efficacy of ozone treatment in reducing common bunt (Tilletia spp.) infection in wheat grains, a significant issue in organic agriculture. Paper III provides a comprehensive evaluation of ozone treatment across various cereal grains, including barley, rye, oats, and different species of wheat, investigating fungal reduction. All three papers evaluate the subsequent effects of ozone on grain germination.

The findings of this research demonstrate that ozone is effective in reducing fungal contamination in a range of cereal grains, with varying efficacy depending on the type of grain, fungal species, and treatment conditions. The effectiveness of ozone is dose-dependent; higher concentrations and longer exposure times lead to greater fungal reductions, although the impact on grain germination also follows a dose-dependent pattern, with negative effects observed beyond certain thresholds. However, significant fungal inactivation can be achieved without compromising seed germination, allowing for the dual benefit of fungal reduction and seed viability. Factors such as grain moisture, relative humidity, and temperature during ozonation had minimal effects on fungal reductions and grain germination, enhancing the practicality and versatility of ozone treatment in various settings. However, storage studies indicate that fungal spores may recover over time, suggesting that ozone treatment may be more fungistatic than fungicidal, warranting further investigation. Additionally, ozone treatment can accelerates drying of seeds, which opens the possibility of treating freshly harvested grains during drying before storage.

In conclusion, this thesis advances the understanding of ozone as a potential alternative to synthetic fungicides in cereal grain disinfection. By providing practical insights into the application of ozone in post-harvest management, this research contributes to the development of more sustainable and effective methods for protecting cereal grains, ultimately supporting global food security and agricultural sustainability.