Microorganisms represent two important problems
for the vegetable and fruit industries: the spoilage or
reduction of shelf life, and human health problems
due to the presence and/or growth of microbial
pathogens that result in cases or outbreaks of foodborne
diseases (Doyle, 1990). Listeria monocytogenes
is of special concern because it can grow at refrigeration
temperatures, persists as an environmental contaminant
in the processing environment, and has the
potential to cause mortalities associated with outbreaks
(Fain, 1996).
Scientific data related to L. monocytogenes in raw
fruits are extremely limited. As of January 1997,
Brackett, 1999 mentioned that only two studies dealing
with viability of listeriae in orange serum and
juice have appeared in the scientific literature. Fruit
peel is a protection against microorganisms; once this
barrier is broken (slices, injured) pulp can be contaminated
and allow the growth of microorganisms.
Studies of growth of L. monocytogenes in low-acid
fruits are almost non-existent.
Parish and Higgins (1989) reported the survival of
L. monocytogenes in sterile orange serum in which
the pH was adjusted from 3.6 to 5.0. For an initial
innoculum of 106 CFU/ml, there was recovery of >25
CFU/ml after 90 days at pH 4.8 and 5.0 with
incubation at 4 jC. At the end of 7-day incubation
at 30 jC, no viable cells were recovered at these