Influence of Frequency, Electric Field Strength, and Nonthermal Factors on the Inactivation of <scp> <i>Escherichia coli</i> O157 </scp> : <scp>H7</scp> During the Ohmic Heating Processing of Pomelo Juice

ABSTRACT The influence of frequency, electric field strength, and nonthermal effects during ohmic heating (OH) on the inactivation of Escherichia coli O157:H7 in pomelo juice was investigated. Pomelo juice was inoculated with a specific density of E. coli O157:H7 and then treated with OH at frequencies ranging from 50 Hz to 20 kHz and electric field strengths of 20, 30, and 40 V/cm. The results showed that 60 and 500 Hz were more effective in inactivating E. coli than other frequencies. As electric field strength increased, inactivation also increased. Transmission electron microscopy analysis revealed that the cell membrane of E. coli O157:H7 treated with OH underwent more pronounced changes than cells treated with conventional heating (CH). OH could inactivate E. coli O157:H7 at lower temperatures and in a shorter time than CH. The nonthermal effect of OH increased the inactivation of the pathogen in pomelo juice. These findings demonstrated the potential of OH for pasteurizing pomelo juice.