Listeria monocytogenes

Although not implicated in a foodborne outbreak associated with fresh juices, other foodborne pathogens do exist that also exhibit a tolerance/resistance to high levels of acid. Given an opportunity to contaminate fresh juice, these acid-resistant organisms could result in foodborne outbreaks. Chief among these possible pathogens is Listeria monocytogenes. L. monocytogenes is ubiquitous within the environment, carried by animals, and frequently found on fruits and vegetables [57-59].

The minimum pH for growth of L. monocytogenes is dependant on the acidulant. For malic acid, the primary acid found in apple cider/juice, the lowest pH value for growth of L. monocytogenes is from 4.4 to 4.6 depending on the strain [60]. Although this pH is somewhat higher than typical fresh apple cider/juice, some apple cider/juice may fall within a range that will allow L. monocytogenes growth, particularly if unsound fruit is used in production. Not all apple cider/juice may have a pH low enough to prohibit growth of L. monocytogenes. In addition, although L. monocytogenes may not grow at lower pH values, survival at lower pH similar to E. coli O157:H7 and salmonella is possible [60,61]. L. monocytogenes has been isolated from unpasteurized apple juice [62]. The recently completed L. monocytogenes risk assessment indicated that consumption of fresh fruit has a low risk for listeriosis [63]. However, two risk factors need to be considered concerning juice-associated listeriosis. First, comingling fruit to make juice or cider spreads the risk over a much larger exposed population, when compared to a single or limited serving size typically associated with the fruit itself. Second, fresh juice is frequently consumed by subpopulations at risk for listeriosis, e.g., children and adults with compromised immune systems. Consequently, it is reasonable to consider as somewhat likely outbreaks or sporadic cases of listeriosis associated with fresh juice.

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