I. Gaska, M. Shur, S. Rumyantsev
Rensselaer Polytechnic Institute,
Keywords: ultraviolet, LED, post harvest, shelf-life
Summary:With the ever-increasing human population within developing countries, limited availability and access to clean water, ever present climate change call for the coming of a second green revolution. An important component of this second green revolution is extending the shelf life of post-harvest fruits and vegetables. Reducing spoilage will result in a net effect of less waste in landfills, lower transportation costs, and a decrease in the consumption of limited freshwater and fertilizers. Existing UV technology involves medium and low-pressure lamps. These systems are bulky, contain hazardous materials, and require extended warm up times. Furthermore, these systems do not function efficiently at lower temperatures required for produce storage. Deep Ultraviolet Light Emitting Diodes (DUV LEDs) provide an energy efficient and hazardous material free solution. Through the implementation of Deep UV LED technology, we have extended the shelf life of several fruits and vegetables using DUV LEDs ranged within 250nm-365nm. During the experiments multiple variables including temperature, humidity, and initial quality of produce were taken into account. Upon illumination of blueberries, raspberries, grapes and strawberries; the shelf life of the aforementioned produce was either increased or displayed no visual membrane degradation. However, DUV LED treatment of bananas accelerated the ripening process significantly. Strawberries were also tested under constant UV illumination alongside pulsed testing. Results revealed that the increase in post-harvest shelf life of strawberries was due to total UV dosage rather than power density distribution. Illumination after one hour at optical output power 18mW/m2 resulted in a total dose of ~65 J/m2, which was enough to prevent mold growth. However, the peak power during illumination in the pulse regime was rather high (1.8W/m2). Dosages greater than 11×103 J/m2were shown to significantly maintain the visual appearance of the strawberries and prevent mold growth for a minimum of 7 days. More research will be conducted in order to optimize the process by significantly increasing the shelf life of post harvest produce while requiring minimum input power. This goal is geared toward providing a simple circuit system power supply to integrate into original equipment manufacturer (OEM) systems. Further innovations within the illumination system design along with research involving the combination of UV activated compounds such as ozone are fundamental in the implementation of the post-harvest ultraviolet technology. These combinations will provide economically viable green technology to improve post harvest produce quality and shelf life.