The reaction mechanisms of ethylene oxide and propylene oxide with food Simulants: Based on experiments and computational analysis.

Ethylene oxide (EO) and propylene oxide (PO) are widely used as sterilizing agents in the food industry. However, their residues in food packaging can migrate into food and react with it, affecting the accuracy of residue detection in food. This study aims to explore the reaction mechanisms between EO and PO and aqueous food simulants using both experimental and computational methods. Especially to investigate the effects of temperature, pH and material structure on these reactions. Experimentally, the stability of EO and PO in different types of aqueous food simulants at 20 °C, 40 °C and 70 °C was observed. It was found that at 20 °C, EO and PO reacted rapidly in 4 % EtOH, which 90 % has reacted in 72 h, and only 10 %-20 % reacted in other types of food simulants. All reactions accelerated with increasing temperature. At 70 °C, all reactions have been completed except for 50 % EtOH, which 80 % has reacted in 72 h. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that EO and PO can form diols or glycol ethers. Computationally, Density Functional Theory (DFT) and Transition State Theory (TST) was used to calculate the energy barriers of the reaction processes. The results showed that the energy barrier for the reaction of EO and PO with water is about 125 kJ/mol. The energy barrier can be reduced by about 40 kJ/mol with acid catalysis. Reactivity at the binding sites was analyzed through the Fukui function (FF), average local ionization energy (ALIE), and electrostatic potential (ESP) analysis. According to the results, the f + value at C7 in PO is 0.041 higher than it at C5. The ESP value of EO is 0.15 kcal/mol higher than that of PO and the ALIE value of EO is also 0.11 eV higher. The experimental results show the impact of temperature, and calculation results highlight the effects of pH and material structure on reaction mechanism. These results can help guide the development of safer packaging materials and provide theoretical support for more accurate detection of residues in food.