Validation of Ohmic Heating Pilot Plant for Vitamin C Retention and <i>E. coli</i> Surrogate Inactivation on Strawberry Nectar

This study validates the performance of a pilot-scale ohmic heating plant for vitamin C retention and <i>Escherichia coli</i> surrogate inactivation in strawberry nectar, based on thermal kinetics determined using a thermoresistometer. Initial experiments with the thermoresistometer established the thermal kinetics of vitamin C degradation and <i>E. coli</i> ATCC 8739 inactivation in surrogate media and strawberry nectar. The use of the thermoresistometer was selected due to its rapid heating mechanism, which closely matches the heating rates of ohmic heating. The <i>D</i> values for the microorganism ranged from 19.8 to 123.6 s, and the activation energy for vitamin C was 25.83 ± 0.48 kJ/mol for the surrogate media and 31.00 ± 2.62 kJ/mol for the nectar. Based on these results, treatments in the pilot-scale ohmic heating system were designed to achieve a 5-log microbial reduction and minimal vitamin C loss. The pilot trial on strawberry nectar demonstrated effective microbial inactivation and a reduction in vitamin C of 17%, which was higher than the calculated 2.7% from thermoresistometer data, likely due to differences in processing conditions. This research confirms that ohmic heating can achieve comparable microbial safety and nutrient preservation to conventional pasteurization, while offering potential advantages in energy efficiency.