Purpose: This study aimed to evaluate growth and survival of Listeria monocytogenes, Salmonella, and Escherichia coli O157:H7 in freshly made orange, apple, and pear juices.
Methods: Juices from locally obtained oranges, apples, and pears were extracted using a Hamilton Beach 67608 Juicer after which sugar content and pH were measured using a refractometer and pH meter, respectively. The juices were inoculated with three-strain virulent cocktails of L. monocytogenes, Salmonella, and E. coli from recent outbreaks to contain ~ three log CFU/ml. Samples of each juice were then stored at 4°C, 10°C, and 22°C with subsamples collected daily over a period of five days for microbiological analysis. Listeria monocytogenes, Salmonella, and E. coli O157:H7 were enumerated by surface-plating appropriate dilutions on trypticase soy agar + yeast extract (TSAYE) containing 0.1% (w/v) esculin and 0.05% (w/v) ferric ammonium citrate, TSAYE containing 0.05% ferric ammonium citrate and 0.03% sodium thiosulfate, and Sorbitol MacConkey Agar after 24 h of incubation. All experiments were conducted in triplicate.
Results: None of the pathogens grew in any of the juices with significantly greater declines seen for Listeria (0.5 to 1.7 log) compared to Salmonella (0.1 to 0.7 log) and E. coli O157:H7 (0.1 to 0.4 log). By day five, both orange and apple juice had visible mold at 22°C. The pH of the apple, orange and pear juice was 3.80±0.1, 3.63±0.2 and 3.95±01, respectively, while the sugar content was 12, 12, and 14°Brix, respectively.
Significance: This study demonstrates the ability of foodborne pathogens to survive in apple, orange, and pear juices during storage at different temperature. Therefore, measures to prevent or eliminate food pathogens in fresh juices and their preparation areas are needed to better ensure end product safety.