Submitted to: Fruit Processing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2004
Publication Date: 5/30/2004
Citation: Geveke, D.J., Brunkhorst, C. 2004. RFEF pilot plant for inactivation of escherichia coli in apple juice. Fruit Processing. 14(3):167-170. Interpretive Summary: The radio frequency electric fields (RFEF) process has been shown to inactivate Escherichia coli in apple juice at moderately low temperatures using a 4 kW radio frequency power supply; however, the maximum flow rate was limited by the power supply to only 0.55 l/min. A novel 80 kW RFEF pilot plant was designed and assembled that processed apple juice at a rate of up to 1.4 l/min. RFEF processing reduced the population of E. coli by 99.8% at 60°C and a hold time of 3 sec, whereas conventional heating at the same conditions had no effect on the E. coli. This work demonstrated that the nonthermal RFEF process can be scaled up to greater flow rates, using higher powered equipment, and pointed toward the likelihood of scaling up the flow to commercially applicable rates.
Technical Abstract: The nonthermal process of radio frequency electric fields (RFEF) is relatively new and has been shown to inactivate bacteria in apple juice at moderately low temperatures. However, the process has only been developed for a flow rate of 550 ml/min. The objective of this study was to scale up the RFEF technique to greater flow rates. A novel 80 kW RFEF pilot plant was designed and assembled that processed apple juice at a flow rate of 1.0 and 1.4 l/min. Escherichia coli K12 in apple juice was exposed to an electric field strength of 20 kV/cm at a frequencies of 21, 30, and 40 kHz. RFEF processing reduced the population of E. coli by 2.7 log at 60°C and a hold time of 3 sec, whereas conventional heating at the same conditions had no effect. Increasing the electric field strength and temperature, as well as decreasing the frequency, enhanced the inactivation.