Apply concentrated high-intensity electric fields for orange juice pasteurization.

Nonthermal processes for food preservation arise from consumers' demands for safe, minimally processed foods that have fresh characteristics and no additives. High-intensity pulsed electric field (PEF) processing involves the application of pulses of high voltage, typically 20 to 80 kV/cm, to foods placed between two electrodes.

PEF treatment is conducted at ambient, sub-ambient or slightly above ambient temperatures for less than 1 second. Energy loss caused by heating is minimized. PEF technology is considered superior to traditional heat treatment because it avoids or greatly reduces the chance for detrimental changes to occur to the sensory and physical properties of foods.

High-intensity PEF technology has received a lot of attention from researchers and food processors, and extensive research has been conducted on this approach to pasteurization. Nonetheless, PEF processing has few large-scale industrial applications because the PEF equipment and the process are very specialized and costly.

Scientists at the University of Minnesota have developed a novel reactor that uses a simple high-frequency AC power supply to generate high-intensity electric fields in liquid food which will then inactivate microorganisms. Compared with the traditional PEF technique, the reactor uses a less expensive power supply, is more energy-efficient and does not have electrode erosion and contamination problems.

The AC-powered concentrated high-intensity electric field (CHIEF) system for liquid food pasteurization features a high-intensity electric field reactor with two electrodes covered by special dielectric materials. High-voltage AC power is applied to the two electrodes between which the liquid foods pass and are treated.

The researchers used orange juice inoculated with E. coli to test the system. Working parameters such as applied electric field, frequency and treatment time were investigated. The results show that the system is capable of killing E. coli in liquid foods and has potential for industrial applications.

Further information. Paul Chen, Department of Bioproducts and Biosystems Engineering, 301 BioAgEng, University of Minnesota, 1390 Eckles Ave., St. Paul, MN 55108; phone: [phone]; email: [e-mail].