Agriculture Reference
In-Depth Information
at the midside and blossom end, with fruit maturity having no pronounced effect on
the rate of internalization. A virtually identical study reported by Brazilian investiga-
tors three years later (Branquinoho Bordini and others 2007) confi rmed the previous
fi ndings with populations of internalized Salmonella at least tenfold higher at the stem
end compared to the midside or blossom end, with these fi ndings supporting a shift
toward nonthermal disinfestation methods such as ionizing irradiation for mangos.
Oranges
Following several widely publicized salmonellosis outbreaks traced to unpasteurized
orange juice in the late 1990s, Eblen and others (2004) conducted a series of experi-
ments to assess the ability of Salmonella and E. coli O157:H7 to infi ltrate both intact
and punctured oranges. When intact Florida and California oranges at 21 °C were
initially immersed in a dye solution at 4 °C, 3 to 4% of the oranges took up the dye
through the stem scar with no dye infi ltration observed when the two temperatures
were reversed, again indicating the importance of a positive temperature differential
for both water and pathogen uptake. Subsequently, oranges tempered to 37 °C were
spot inoculated at the stem scar with an E. coli O157:H7 or S. Enteritidis dye solution
containing 10 7 CFU/ml and then equilibrated for 3 h at 4 and 24 °C, respectively.
Overall, 2.5 to 3.0% of these oranges yielded the target pathogen, with 0.1% of the
E. coli O157:H7 and 0.01% of the Salmonella inoculum internalized, giving popula-
tions of 3.82 and 2.34 log CFU/g, respectively. Introducing three evenly spaced
0.91 mm diameter/1.5 cm deep holes opposite the stem scar increased Salmonella
uptake to 31% with pathogen growth observed during subsequent storage at 24 °C,
presumably between the segments and pulp vesicles due to a more favorable pH.
Hence, these fi ndings confi rm the potential public health hazard of processing warm,
damaged, or otherwise punctured fruit for juice.
Tomatoes
Problems regarding tomatoes with premature bacterial soft rot of tomatoes exiting
commercial dump tanks during the 1970s prompted several studies that confi rmed the
ability of water and subsequently spoilage bacteria to infi ltrate tomatoes through
cracks that formed when warm fruit was immersed in colder water (Segall and others
1977). Bartz and Showalter (1981) clearly demonstrated that an increase in tomato
weight resulting from exposure to a negative fruit/water temperature differential led
to increased infi ltration by several spoilage bacteria, particularly in the scar stem area
of green tomatoes as was fi rst reported 28 years earlier by Samish and others (1963a),
with increased bacterial penetration seen in more deeply submerged tomatoes as a
result of increased hydrostatic pressure.
At least 12 multistate outbreaks of salmonellosis, including approximately 2,000
culture - confi rmed cases, have been traced to tomatoes since 1990 (Bidol and others
2007), raising concerns regarding growth, survival, and inactivation of salmonellae.
When an outbreak strain of Salmonella Montevideo was introduced into the core tissue
of mature green tomatoes using a
15 °C temperature differential between the fruit and
immersion water, Zhuang and others (1995) showed that populations in the core tissue
increased
tenfold during 18 days of storage at 20 °C, but remained unchanged or
declined when stored at 10 °C. However, certain proteolytic yeasts and molds in
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