2-13.
MICROBIOLOGY OF FRUITS
The microorganisms found on fruits may be divided into three different groups.
These three groups are spoilage organisms, organisms essential to fermentation, and
pathogenic organisms.
a. Intestinal Diseases. Of the different groups of diseases, those classified as
intestinal diseases are most likely to be transmitted by fruits. The organisms
responsible for intestinal diseases are soil and water organisms, so they have an
excellent opportunity to contaminate fruits. Fresh fruits are a major cause of concern
because they are generally eaten raw and are seldom properly cleaned before they are
eaten. Some of the fresh fruits that commonly serve as vehicles for disease
transmission are apples, bananas, grapes, lemons, oranges, and peaches. Cholera,
dysentery, diarrhea, and typhoid fever are the intestinal diseases most likely to be
caused by organisms found on fresh fruits.
b. External Contamination. The meat of fruits is generally sterile. The
disease-transmission potential of fresh fruits, then, is derived from external
contamination. Even a break in the skin of citrus fruits will not result in the meat
becoming contaminated because the acid content is high enough to kill most bacteria.
Contaminated grapes used in wine production are of little concern because pathogenic
organisms are destroyed by the wine. The packaging and packing materials may
contaminate fresh fruits. Anthrax spores have been found on hides in which lemons
were shipped from Spain to England. It would be entirely possible for any other
packaging or packing materials to contaminate fresh fruits. Staphylococcus aureus is a
common contaminant of fresh fruits and can readily be introduced to salads. Food
poisoning could result if the salad provided a proper medium and the temperature of the
salad was in the growth range for Staphylococcus aureus organisms. Contamination of
fresh fruits will usually result from direct contact with the soil on the farm; dust on the
farm, and from handling at the packing shed or market.
2-14. MICROBIOLOGY OF VEGETABLES
a. External Contamination. The tissues of vegetables are normally sterile.
The problem with contamination is the same as with fruits. External contamination is
the only problem worthy of practical consideration. Since the edible portions of
vegetables are grown in or near the ground, they are very susceptible to contamination
by soil microorganisms. Vegetables are also likely to be contaminated by dust on the
farm and contaminated irrigation water. Fresh vegetables are often processed and
packed under unsanitary conditions, and they are likely to be contaminated while being
processed and packed. Washing vegetables often does little to remove contaminants.
In the case of leafy vegetables, washing does more harm than good. In studies
conducted on lettuce, it was found that the heads were more thoroughly contaminated
following washing than before washing. This is because the outer leaves are more
heavily contaminated, and washing distributes the contaminants throughout the head.
Human fecal material is used as fertilizer in many parts of the world, and vegetables
grown under such conditions present a major problem by serving as vehicles for the
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