Effect of ozone, treatment temperature, and antimicrobials on inactivation of Escherichia coli O157:H7 and Salmonella spp. in apple cider and orange juice

Inactivation of E. coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone (0.9 g ozone/h) at 4, ∼20, and 50°C was evaluated. After treatment at 50°C E. coli O157:H7 populations were reduced by >5 log cfu/ml in cider and orange juice within 45 and 75 min, respectively. At 50°C Salmonella populations were reduced by 4.8 and >5 log cfu/ml in 15 min in cider and orange juice, respectively. E. coli O157:H7 in cider (180 min) and orange juice (240 min) at 4°C was reduced by 4.8 and >5 log cfu/ml, respectively. Salmonella in cider (180 min) and orange juice (240 min) at 4°C was reduced by 4.5 and 4.2 log cfu/ml, respectively. E. coli O157:H7 and Salmonella populations in cider and orange juice at ∼20°C decreased by <5.0 log cfu/ml during 240 min. Two additional studies were conducted to determine inactivation of E. coli O157:H7 and Salmonella in cider and orange juice treated with ozone in combination with antimicrobials. Ozone (O₃; 0.9 g ozone/h) was bubbled into juices (4°C) containing either dimethyl dicarbonate (DMDC; 250 ppm) or hydrogen peroxide (HP; 300 ppm) for up to 90 min [Study 1] and DMDC (250 and 500 ppm) or HP (300 and 600 ppm) for up to 60 min followed by 24-h storage at 4°C [Study 2]. Study 1: All treatments resulted in <5 log reduction of either pathogen. However, O₃/DMDC (250 ppm) was more effective than O₃/HP (300 ppm) for reducing populations of E. coli O157:H7 and Salmonella, and greater inactivation occurred in cider than in orange juice (P < 0.05) Study 2: All treatment combinations, followed by refrigerated storage, caused >5-log reduction of E. coli O157:H7 and Salmonella in cider and orange juice, except O₃/DMDC (250 ppm) treatment in orange juice reduced E. coli O157:H7 populations by <5 log cfu/ml. For all combinations tested, inactivation of E. coli O157:H7 and Salmonella was greater in cider than in orange juice, and O₃/DMDC caused greater reductions than O₃/HP (P < 0.05).