Agriculture Reference
In-Depth Information
(2002) placed apples on
E. coli
-inoculated topsoil in a controlled outdoor setting, the
organism entered the outer and inner core as well as the skin and pulp within 1 day.
Apple orientation dictated the extent of internalization with highest
E. coli
populations
found in the outer core when the apple calyx directly contacted the soil.
Cantaloupe
Salmonella
is a frequent contaminant of cantaloupe with at least 11 such multistate
outbreaks reported to the Centers for Disease Control and Prevention since 1973, 5
of which were traced to
Salmonella
Poona, a serovar infrequently associated with
human foodborne illness (Bowen and others 2006). Although most often confi ned to
the outer rind of cantaloupes in biofi lms (Annous and others 2005; Beuchat and
Scouten 2004; Richards and Beuchat 2004),
Salmonella
can also penetrate the stem
scar tissue and wounds, particularly when these areas become colonized by certain
phytopathogenic molds (Richards and Beuchat 2005a,b).
In the fi rst of two studies by Richards and Beuchat (2004), Eastern cantaloupes at
30 ° C were signifi cantly heavier after immersion in a
S.
Poona suspension at 4 ° C
compared to cantaloupes at 4 or 30 °C that were immersed in a 30 °C inoculum.
Although these fi ndings were expected based on pressure differences, Western canta-
loupes were similar in weight regardless of the treatment with these fi ndings perhaps
related to their far denser surface netting leading to greater retention of surface water.
When aqueous suspensions of
S.
Poona (
9 log CFU/ml) at 4 and 30 ° C were used for
immersion, greater infi ltration of
S.
Poona into the rind was seen using Eastern can-
taloupes at 4 (5.0 log CFU/cm
2
) rather than 30 ° C (4.56 - 4.74 log CFU/cm
2
) regardless
of the water temperature. In contrast, higher numbers of salmonellae were recovered
from the rinds of Western cantaloupes immersed in a 4 °C suspension, regardless of
the cantaloupe temperature. However, all treatment combinations yielded similar
penetration of
S.
Poona into the stem scar tissue of both cantaloupe varieties. The fact
that these bacterial infi ltration fi ndings contradict those previously reported for apples
and tomatoes is likely again related to the complex surface topography of cantaloupes.
Richards and Beuchat (2005a) subsequently reported that
S. Poona
could also migrate
to a depth of 3-4 cm in cantaloupes that had been wound-inoculated at a depth of
4 mm, with infi ltration enhanced in the presence of two phytopathogenic molds:
Cladosporium cladosporioides
and, to a lesser extent,
Penicillium expansum
. Hence,
consumption of damaged or decaying cantaloupe many pose an increased risk of
illness.
∼
Mangos
Being prone to fl y larvae infestations, United States regulations require that all
imported mangos be disinfested by hot water immersion, irradiation, or other proven
means. Immersing mangos in 46.1 °C water for 65 to 90 min as required by the regula-
tion leads to a positive temperature differential during subsequent cooling along with
potential introduction of foodborne pathogens. In response to a 1999 salmonellosis
outbreak in the United States, mangos heat-treated at 46.1 °C for 90 min were sub-
jected to a 22 °C/10 min immersion treatment in water inoculated to contain 7 logs
S
.
Enteritidis CFU/ml (Penteado and others 2004). Immediately after treatment, the stem
ends from 5 of 6 mangos yielded internalized
Salmonella
. Less infi ltration was seen
