Antibacterial Activity of Hydrogen Peroxide Against Escherichia Coli O157:H7 and Salmonella Spp. in Fruit Juices, Both Alone and in Combination With Organic Acids

The antibacterial efficacy of hydrogen peroxide treatments in four fruit juices was determined. Preservative free apple cider, white grape, and purple grape juice were inoculated with ~ 6.4 log CFU/ml of a five strain, acid adapted, nalidixic acid resistant E. coli O157:H7 cocktail. Orange juice was inoculated with a comparable Salmonella spp. cocktail. In the first study, 0.017% and 0.012% H₂O₂ was added in combination with 0.1% and 0.3% of the dominant organic acid (OA) to 4°C and 25°C juices, with samples taken each day for 21 days. H₂O₂ was a significant factor in all juices (p < 0.05) except white grape (lack of data), and both 0.017% H₂O₂ treatments reduced counts in apple cider, orange juice, and white grape to undetectable numbers within 48 hrs as cultured on tryptone soy agar + 0.05% nalidixic acid (TSAN). Treatments in purple grape juice were less effective overall, and more dependent on OA concentration (p < 0.001) than H₂O₂.

There were instances where bacterial survival in apple cider, purple grape, and orange juice continued for 21 days after treatment, and sometimes outlasted the control. These occurrences were dependent on temperature (25°C) and H₂O₂ (0.012%), but not on OA. However, OA concentration was a significant factor (p < 0.05) overall in apple cider and purple grape juice, but not in orange juice.

In the second study, 0.015% and 0.03% H₂O₂ was added to 10, 25, and 40°C apple cider and orange juice inoculated with 6.4 log CFU/ml E. coli O157:H7 and Salmonella spp. respectively. Only 0.03% H₂O₂ was effective in reducing counts to undetectable numbers in both juices. However, both temperature and H₂O₂ were significant factors (p < 0.0001) in bacterial destruction, with 0.03% H₂O₂ at 40°C giving undetectable numbers at ≤ 3 and ≤ 6 hours in orange juice and apple cider respectively.

It has been demonstrated that at ~ ≥ 0.017%, H₂O₂ can provide a 5 log reduction of these pathogens in fruit juice. Increasing temperature and organic acid concentration can improve its rate of effectiveness in certain juices. However, sensory concerns may negate its use in some products.