Bacterial Infiltration and Internalization in Fruits and Vegetables 453
and level of hydrostatic pressure. When submerged in water fresh produce may
endure bacterial infiltration mainly because of the interaction of these two factors
(Bartz, 1999). The combined effect of temperature differential and hydrostatic pres-
sure on fresh produce cannot be evaluated by simple calculations. This statement is
supported by research data indicating that higher temperatures in immersion depth
studies resulted in increased infiltration (Bartz, 1982). More importantly, previous
research has shown that infiltration of water can occur almost instantaneously under
certain conditions of temperature and hydrostatic pressure (Bartz and Showalter,
1981). However, when the temperature of wash water and hydrostatic pressure are
controlled, produce have to be immersed in water long enough during cooling to
facilitate infiltration (Bartz and Showalter, 1981; Bartz, 1999).
14.5.2.2 Prevention of Infiltration
Based on current knowledge of bacterial infiltration in fruits and vegetables, inter-
ventions to prevent this problem are needed from cultivation to processing. Preven-
tive measures should be applied at production steps wherever factors that contribute
to bacterial infiltration are identified. Certainly, it might be particularly difficult to
control this problem in fields and orchards. However, interventions applied at key
points in the production of fresh produce can provide an extra margin of safety
against bacterial infiltration. Also, the use of a sanitizer combined with conditions
to prevent bacterial infiltration during washing of fresh produce is likely to prove
more effective than either intervention used separately.
A multifaceted approach to preventing bacterial infiltration in fresh fruits and
vegetables should include good agricultural practices, thorough screening of produce
for visible damage, and a combination of bactericidal and infiltration control inter-
ventions during washing. Previous studies have demonstrated the capability of
human enteric pathogens such as Salmonella and E. coli O157:H7 to infiltrate fruits
and vegetables in contact with contaminated moist soil or manure (Guo et al., 2002;
Solomon et al., 2002; Seeman et al., 2003). Therefore, the use of good manufacturing
practices, including avoiding the use of animal manure or application of thoroughly
composted manure, and irrigation of crops with potable water, will minimize con-
tamination of fruits and vegetables with pathogenic bacteria.
It is well recognized that food crops may sustain physical damage in the natural
environment. For example, dropped fruit may develop cuts or bruises upon impact
with the ground. Such damage will predispose fruits to bacterial infiltration. Also,
the impact with which fruits hit the ground may force bacteria into protected sites
on the fruit surface. This problem is further exacerbated if the soil is contaminated
with animal feces that carry human pathogens. Dropped apples used to make apple
cider were linked to at least two outbreaks of E. coli O157:H7 infections (Besser et
al., 1993; Health Canada, 1999). Dingman (1999) reported that 8 of 11 orchard
owners in Connecticut admitted to using dropped apples to produce cider that was
incriminated in another outbreak. It is therefore important to avoid using dropped
fruit in the production of juices and apple cider that may not be subjected to
bactericidal interventions to eliminate human pathogens. Also, stringent culling of
fruits and vegetables with visible damage is important to reduce the incidence of