transmission of many diseases. We stated above that the tissues of vegetables are
sterile; therefore, microbial contamination is a problem only from external
b. Two Groups. The microorganisms of significance found on vegetables may
be divided into two basic groups. These groups are spoilage organisms and pathogenic
organisms.
c. Raw Vegetables as a Health Hazard. The vegetables most likely to be
involved in disease transmission are those that are eaten raw. Celery endive, lettuce,
onions, parsley, radishes, tomatoes, and watercress are considered as the vegetables
presenting the greatest health hazard. Watercress, because of the manner in which it is
grown, has the greatest disease-transmission potential of any of the above vegetables.
One typhoid epidemic in Philadelphia was traced to the consumption of contaminated
watercress at a banquet. Watercress sandwiches were served at this banquet, and
eighteen of nineteen people who ate these sandwiches contracted typhoid fever.
d. Intestinal Disease Organisms. The intestinal diseases are the most
important group of diseases transmitted by fresh vegetables. Intestinal parasites,
cholera, dysentery, diarrhea, and typhoid fever are most often involved in the
consumption of contaminated fresh vegetables. Typhoid fever is the most important
disease contracted from the consumption of contaminated fresh vegetables in the
United States. Salmonella typhi, the causative organism of typhoid fever, will remain
viable in contaminated soil from twenty-nine to fifty-eight days. This organism is most
often introduced into the soil by contaminated irrigation water. In a survey conducted on
fresh vegetables in the produce markets in Chicago, coliform organisms were found to
be a common contaminant. Escherichia coli organisms were found on 31.5 percent of
the fresh vegetables, and 78.3 percent of the fresh vegetables were contaminated with
some type of coliform organism. (These microorganisms are a common source of acute
diarrhea.) Coliform organisms grow under conditions considered optimum for the
typhoid organisms, so if typhoid organisms had been present in the soil in which these
vegetables were grown, or any of the workers at the produce markets had been carriers
of typhoid, then a large percentage of these vegetables would have undoubtedly been
contaminated with typhoid organisms.
2-15. MICROBIOLOGY OF CANNED FRUITS AND VEGETABLES
a. Commercial Sterility. If all microorganisms in a can of food are destroyed,
then the food should keep indefinitely, as far as microorganisms are concerned. Slow
chemical changes rather than microorganisms often render canned foods inedible.
There are reports of canned food that was edible after 20 to 100 years of storage. It is
possible to sterilize any canned food product, but the food might be changed to such an
extent that it would be unfit for sale. Food canners, then, don't strive for sterility, but
instead settle for "commercial sterility." This entails the destruction of the most resistant
organisms normally present that are capable of causing spoilage. The real question is
not whether viable bacteria are present, but instead whether the food is wholesome and
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