Development and Evaluation of an Ultraviolet Radiation Assisted with Ohmic Heating System for Preservation of Pineapple Juice

An Ultraviolet (UV) radiation assisted with Ohmic heating (OH) system was developed and evaulated on microbial inactivation and on selected quality attributes (colour, pH, Brix Vitamin-C) in pineapple juice has been investigated. Due to the germicidal effect of UV, it has been widely used for fresh produce processing; however, UV application is limited to surface treatment due to low penetration depth. On the other hand ohmic heating causes deterioration of heat-sensitive nutrients within food by excessive current flow. This study was intended to evaluate the effect of UV radiation assisted with ohmic heating on the inactivation and of microorganisms in pineapple juice without the loss of nutritional values. Juice was passed through two cylindrical chambers Ohmic heating chamber and UV chamber. Juice sample (1500 mL) were pasteurized with UV treatment (800 and 1200 mJ/cm²), ohmic treatment (50°C and 55°C) and ohmic heating combined with UV treatment as the temperature and dosages rose to 50°C/800 mJ/cm2, 55°C/1200 mJ/cm². The highest lethal rate (5.19 log reduction) of bacterial population was obtained for samples treated with the UV/ohmic heating combination at 50°C/1200mJ/cm², which may be due to the effects of UV radiation assisted by ohmic electrophoresis effectively penetrating into cell membranes, leading to cell disruption and inhibition of cell replication. Therefore, ohmic heating combined with UV treatment has the potential to improve the inactivation of microorganisms in pineapple juice and other liquid foods, finally ensuring safety of juice products.