We also found that the effectiveness of sanitizers varied
depending on the apple surface condition. On apples with cut
surfaces, the effectiveness of sanitizers was significantly inhibited.
This may be because the cut surfaces of fruits and vegetables
release liquids, which microorganisms readily attach to and use for
nutritive purposes. For example, E. coli O157:H7 cells attached
preferentially to damaged tissues surrounding puncture wounds
in the skin of apples and heavily colonized these damaged sites up
to 70 mm below the tissue surface (Burnett et al., 2000). When
fruits are damaged, the bactericidal effects of sanitizers (chlorine
sanitizer and lactic acid) are lower than they would be for unblemished
fruits. In addition, the injured plant tissues release
liquids at the cut surface, which also interferes with the sanitizing
action of initial wash steps, making them less effective (Matthews,
2006). For these reasons, we found that the effectiveness of the
chlorine sanitizer and 2% lactic acid on killing pathogens was
reduced for produce with damaged surfaces. Unfortunately, it is
inevitable that some surfaces of produce will be damaged during
transportation and thus be more difficult to clean or sanitize. More
efforts should be made to avoid incurring these damages. Also,
new sanitizing methods, such as using physical treatment rather
than or in addition to using liquid sanitizer, need to be developed
for cleaning and sanitizing damaged or minimally processed fresh
produce.
Montevideo to the surfaces of tomatoes and tomatillos. In studying
the effects of surface condition on the survival of pathogens, Ells
and Truelstrup Hansen (2006) found that the condition of cabbage
surfaceswas an important factor for pathogen attachment and
that colony counts from cut surfaces were significantly higher
compared to those of intact surfaces. In our study, there was not a
reduction in pathogen levels on cut apple surfaces for all RH levels.
In other words, surface condition was an important factor for
pathogen survival. We concluded from these results that RH levels
and surface conditions were related to the survival of pathogens
contaminating the surface of fresh fruits. As such, fresh fruits
should be stored, prepared, and processed in refrigerated conditions
with low RH. It is also important to avoid damaging the surface
of the fruit to enhance the safety of its consumption.