genic bacteria (Brackett, 1992). Washing with
water can also result in cross-contamination.
Chlorinated water is the most frequently used
sanitizer for the washing of fresh produce.
However, this treatment has minimal effect
and results in less than a 2 log CFU/g reduc-
tion of pathogens on fresh produce (Beuchat
et al., 1998). Other sanitizers such as chlorine
dioxide, hydrogen peroxide, organic acid, cal-
cinated calcium solution, ozone, and acidic
electrolyzed water have the same minimal
antimicrobial effect as chlorinated water (Bari
et al., 1999; Han et al., 2000; Kim et al., 1999;
Lin et al., 2002; Koseki, 2003). Acidic elec-
trolyzed water has effectively inactivated
pathogens such as Escherichia coliO157:H7,
Listeria monocytogenes, Salmonella, and
Bacillus cereus(Kim et al., 2000; Koseki et al.,
2001; Park et al., 2001).
Soil Contamination
Heat-resistant bacteria are present in the
ground and can cause “flat sour” and other
spoilage of canned vegetables if washing is
not thorough. Microbial population is
affected by the degree of wind, humidity,
sunlight, and temperature, as well as by
domestic and wild animals, irrigation water,
bird droppings, harvesting equipment, and
workers. Most pathogens are introduced to
fruits and vegetables via irrigation shortly
before harvesting and before the sun dehy-
drates and destroys pathogens.
Air Contamination
Contaminated air contributes to less sani-
tary raw products. Besides normal microor-
ganisms and pollutants found in the air, this
medium serves as a transport of pathogens.
Infiltration of unclean air into the processing
plant can be improved by the use of air filters.
Pest Contamination
Certain pests can invade fruits and vegeta-
bles during the process of forming on the tree
or vine. Contamination by pests can be
expressed through the spread of viruses,
spoilage bacteria, and pathogens, as well as by
physical damage. Infesting microorganisms
frequently remain inactive because of the pro-
tective skin layer of fruits and vegetables and
because of the low availability of moisture
(measured as minimum water activity [AW])
on the surface. As these products reach matu-
rity or shortly thereafter, profound changes in
the medium can cause spoilage. The action of
pests, such as the pollinating fig wasp
(Blastophaga psenes), introduces microbes
that persist and develop in quantity through-
out the ripening period until the fruit is
mature. Although a portion of the microor-
ganisms introduced does not cause spoilage,
these microbes attract other organisms, such
asDrosophila, which carries spoilage yeasts
and bacteria. When the protective covering of
fruits and vegetables is broken by bruises,
mechanical injury, or by attack of insects,
microorganisms can enter readily.
The presence of coliforms on processing-
grade fruit as it arrives at the processing
plant is not truly indicative of the amount of
these microorganisms in the manufactured
juice or of positive evidence of unsanitary
conditions in the processing plant. However,
the presence of lactic acid bacteria consti-
tutes an accurate index of processing sanita-
tion for high-quality frozen citrus products.
Lactic acid bacteria are a more accurate indi-
cator of unsanitary conditions caused by
inadequate cleaning because these microor-
ganisms are the most likely to accumulate in
the bacterial pools that can exist when
proper sanitation practices are not followed.
Although several mycotoxins occur in
nature, few are regularly found in fruits. The
formation of mycotoxins depends more on
endogenous and environmental factors than
does fungal growth. Mycotoxins may remain
in fruits even when the fungal mycelium has
been removed. The diffusion of mycotoxinsFruit and Vegetable Processing Plant Sanitation 337