Efficacy of photocatalysis and photolysis systems for the removal of ethylene under different storage conditions

Most fresh horticultural commodities are highly perishable and ethylene often plays an important role in their ripening and senescence process. Reduction of ethylene concentrations around these commodities may lead to the slowing down of metabolic processes, which could potentially extend their storage or shelf life. The objective of this work was to investigate photocatalytic oxidation (PCO) and vacuum ultraviolet light (VUV) photolysis for ethylene removal in fruit storage. The efficacy of both techniques for ethylene removal was analyzed under different storage conditions (initial ethylene concentration, oxygen, relative humidity and temperature). Ethylene removal in VUV photolysis was much faster than PCO with the reaction mechanism followed by Langmuir-Hinshelwood and first-order equations, respectively. Higher O2 concentration in the reactor favored both ethylene removal processes. However, high relative humidity impeded PCO and enhanced VUV photolysis efficacy of ethylene oxidation. Lowering the temperature from 21 °C to 1 °C showed no consistent trend of temperature effects on ethylene removal in the PCO process, whereas in VUV photolysis, reducing the temperature decreased ethylene removal significantly (p ≤ 0.05). Ethylene removal in a gas stream with a single pass through VUV photolysis reactor was 84.8% whereas it was only 14.9% in PCO reactor. Apple storage revealed that the ethylene concentration increased to 70 μL L−1 in 8 days at 1 °C. This concentration was brought down to 24 and 2.6 μL L−1 in storage chambers connected to PCO and VUV reactors, respectively. Further research efforts are needed to improve the performance of the reactors for the complete removal of ethylene in postharvest storage of fresh produce.