Effect of Hyperbaric Pressure Treatment on the Growth and Physiology of Bacteria that Cause Decay in Fruit and Vegetables

The response of bacteria to hyperbaric pressure treatment was investigated. Three selected bacteria which cause fruit and vegetable decay (i.e., Pseudomonas cichorii, Pectobacterium carotovorum, and Pseudomonas marginalis) were inoculated onto BIOLOG microplates and subjected to different pressure and temperature conditions including 100, 200, 400, 625, and 850 kPa at 20 A degrees C and 100 kPa at 4 A degrees C. Changes in microplate color, which corresponds to carbon source utilization of bacteria or their growth, were monitored every 24 h for 7 days. Results showed that the bacterial growth was affected by both hyperbaric pressure and temperature. As hyperbaric pressure increased, the bacterial growth significantly decreased and the extent was dependent on bacterial species. The 850-kPa pressure treatment reduced maximum growth by 71, 56, and 43 % for Pseudomonas cichorii, Pectobacterium carotovorum, and Pseudomonas marginalis, respectively. Among these bacteria, Pseudomonas cichorii was the most pressure-sensitive, while the most temperature-sensitive was Pectobacterium carotovorum. In general, an increase in hyperbaric pressure caused bacteria to utilize carbon sources similar to those when they were exposed to low temperature. Overall, hyperbaric treatment has the potential to directly reduce bacterial growth in fruit and vegetables after harvest.