Ethylene is a growth hormone emitted by fresh fruits during storage. Importantly, ethylene quickens the process of ripening and softens the tissues in fruits. As a result, the fresh produce rapidly deteriorates in quality and nutrition. Extending the shelf-life of fruits invariably involves controlling the concentration of ethylene in the package space. Modifying the composition of the packaging material is one of the important strategies to control the concentration of ethylene and consequently extend the shelf life of the fruits. Introduction of “active components” such as zeolites, molecular sieves and clay minerals into the packaging material adsorb ethylene produced by the fruits. Commercial packaging materials with such active adsorbents are marketed. However, as the adsorbents get saturated with ethylene over a period of time, they become inactive and inefficient. Hence, packaging material with adsorbents are limited in reuse. Use of oxidants such as KMnO4 in the packaging material is also reported. KMnO4 chemically oxidizes ethylene to CO2 and H2O, and in the process, gets converted to MnO2. Concerns of leaching of KMnO4 or MnO2 onto food products, and the safe disposal of used packaging material consisting the byproduct overweigh the advantages.
Photochemical oxidation of ethylene using vacuum UV to CO2 and H2O is an effective way to manage ethylene. However, due to the high energy of the radiation, O2 in the air forms traces of O3, which can have serious effect on the health of the plant tissues. Photocatalytic oxidation of ethylene is a promising and an upcoming technology. Here, a solid material called photocatalyst is used to make a composite along with the polymers commonly used for packaging. The photocatalyst in the composite absorbs UV light and use the energy to convert ethylene to CO2 and H2O. The photocatalyst is expected to operate only when exposed to light for a certain amount of time. Also, the catalyst is usually durable for a long time without deactivation and hence, in principle, can be reused several times. Among the photocatalysts that are known to catalytically convert ethylene, TiO2 (with modifications) is a promising material.