This slide gives an overview on the topic Contamination, Preservation & Spoilage of Vegetables. Contamination It has been estimated that 1/4th of all product harvested is spoiled before contamination. Spoilage of fresh vegetables usually occurs during storage and transport and while waiting to be processed. Vegetables may be dried, fresh, frozen, fermented, pasteurized or canned. During transportation to market or the processing plant, mechanical damage may increase susceptibility to decay and growth of micro organisms may take place. Recirculated or reused water for washing of vegetables likely to add organisms and the washing process may moisten surfaces enough to permit growth of organisms. Sorting spoiled vegetables or trimming spoiled parts removes micro organisms, but additional handling may result in mechanical damage and therefore greater susceptibility to decay. Spraying with water or packing with chipped ice is done. This spraying gives a fresh appearance to the vegetables and delays decomposition but also adds organisms, e.g. psychrotrophs, from water or ice and gives a moist surface to encourage their growth on longer storage. Sweating of products during handling increases the number of micro organisms in them. Processes such as trimming, mechanical abrasion or peeling, cutting, pitting or coring, and various methods of disintegration may add contaminants from the equipment involved. Examples of possible source of contaminants of foods with micro organisms are trays, bins, tanks, pipes, flumes, tables, conveyer belts and aprons, filters, blanchers, presses, screens, and filters. Inclusion of decayed part of fruits increases the number of micro organisms in fruit juices. Added ingredients such as sugars and starch may add spoilage organisms, specially spores of thermophilic bacteria Spoilage The deterioration of raw vegetables result from physical factors, action of their own enzymes, microbial action, or combination of these agencies. Mechanical damage resulting from action of animals, birds, or insects or from bursting, wounding, cutting, freezing, desiccation, or other mishandling may predisposed towards increased enzymatic action or the entrance or growth of micro organisms. Contact with spoiling vegetables may bring about transfer of organisms, causing spoilage and increasing the wastage. If oxygen is available, the plant cells will respire as long as they are alive, and hydrolytic enzymes can continue their action after death of their cells. Disease of vegetables and fruits may result from the growth of an organisms that obtains its food from the host and usually damages it or from adverse environmental conditions that cause abnormalities in functions and structures of the vegetables or fruits. AGENTS OF SPOILAGE Black mold rot, caused by Aspergillus Niger. Black rot, often caused by species of Alternaria but sometimes of Ceratostomella, Physalospora and other genera. Pink mold rot, caused by pink spored Trichothecium roseum.

1. CONTAMINATION,
PRESERVATION & SPOILAGE
OF VEGETABLES
Presented By
NIZAM ASHRAF
Ist yr MSc. MMD

2. CONTAMINATION
• It has been estimated that 1/4th of all product harvested is spoiled
before contamination.
• Spoilage of fresh vegetables usually occurs during storage and
transport and while waiting to be processed.
• Vegetables may be dried, fresh, frozen, fermented, pasteurized or
canned.

3. • During transportation to market or the processing plant, mechanical
damage may increase susceptibility to decay and growth of micro
organisms may take place.
• Recirculated or reused water for washing of vegetables likely to add
organisms and the washing process may moisten surfaces enough to
permit growth of organisms.
• Sorting spoiled vegetables or trimming spoiled parts removes micro
organisms, but additional handling may result in mechanical damage
and therefore greater susceptibility to decay.
• Spraying with water or packing with chipped ice is done. This spraying
gives a fresh appearance to the vegetables and delays decomposition
but also adds organisms, e.g. psychrotrophs, from water or ice and
gives a moist surface to encourage their growth on longer storage.
• Sweating of products during handling increases the number of micro
organisms in them.

4. • Processes such as trimming, mechanical abrasion or peeling, cutting,
pitting or coring, and various methods of disintegration may add
contaminants from the equipment involved.
• Examples of possible source of contaminants of foods with micro
organisms are trays, bins, tanks, pipes, flumes, tables, conveyer belts
and aprons, filters, blanchers, presses, screens, and filters.
• Inclusion of decayed part of fruits increases the number of micro
organisms in fruit juices.
• Added ingredients such as sugars and starch may add spoilage
organisms, specially spores of thermophilic bacteria

5. SPOILAGE
• The deterioration of raw vegetables result from physical factors,
action of their own enzymes, microbial action, or combination of
these agencies.
• Mechanical damage resulting from action of animals, birds, or insects
or from bursting, wounding, cutting, freezing, desiccation, or other
mishandling may predisposed towards increased enzymatic action or
the entrance or growth of micro organisms.
• Contact with spoiling vegetables may bring about transfer of
organisms, causing spoilage and increasing the wastage. If oxygen is
available, the plant cells will respire as long as they are alive, and
hydrolytic enzymes can continue their action after death of their cells.

6. • Disease of vegetables and fruits may result from the growth of an
organisms that obtains its food from the host and usually damages it
or from adverse environmental conditions that cause abnormalities in
functions and structures of the vegetables or fruits.

7. AGENTS OF SPOILAGE
• Black mold rot, caused by Aspergillus Niger.
• Black rot, often caused by species of Alternaria but sometimes of
Ceratostomella, Physalospora and other genera.
• Pink mold rot, caused by pink spored Trichothecium roseum.
• Fusarium rots, a variety of types of rots caused by species of
Fusarium.
• Green mold rot, caused usually by species of Cladosporium but
sometimes by other green spored molds, e.g. Trichoderma.
• Brown rot, caused by Sclerotinia species.
• Sliminess or souring, caused by saprophytic bacteria in piled, wet,
heating vegetables.

8. • Bacterial soft rot, caused by Erwinia carotovora and related species.
• Grey mold rot caused by species of Botrytis.
• Rhizopus soft rot, caused by species of rhizopus.
• Anthracnose, usually caused by Colletotrichum lindemuthianum.
• Alternaria rot, caused by Alternaria tenuis and other species.
• Blue mold rot, caused by species of Penicillium digitatum and other
species.
• Downy mildew, caused by species of Phytophthora, Bremia, and other
genera.
• Watery soft rot, caused chiefly by Sclerotinia sclerotiorum.
• Stem end rots, caused by species of molds of several genera, e.g.
Diplodia, Alternaria, Phomopsis, Fusarium, and others.

9. PRESERVATION
• Adequate control of temperature and humidity will reduce the
growth of micro organisms.
• Boxes, lugs, baskets and other containers should be practically free of
the growth of micro organisms, and some will need cleaning and
sanitation between uses.
• Contamination from equipment at the time of processing plant can be
reduced by adequate cleaning and sanitizing.

10. Preservation is done by various methods:
• Removal of micro organisms through washing of vegetables which
removes most of the contamination on the surface but leaves much
of the natural microbial flora. Unless the washed water is of good
bacteriological quality, it may add organisms and subsequently
growth may take place at the moist surface.
• Use of heat: Vegetables to be dried or frozen, and some to be
canned, are scalded or blanched to inactivate their enzymes.
• Use of low temperature: A few kinds of vegetables that are relatively
stable, such as root crops, potatoes, cabbage, and celery, can be
preserved for a limited time by common or cellular storage.

11. • Chilling: Most vegetables to be preserved without special processing
are cooled promptly and kept at chilling temperature. The chilling is
accomplished by use of cold water, ice, or mechanical refrigerator or
by vacuum cooling. In many cases precooling, i.e. cooling before
normal cold storage is done immediately after harvesting by use of a
cold water spray, a practice referred to as hydro cooling.
• Freezing: The washing of vegetables reduces the numbers of some
organisms and add some organisms, and scalding or blanching( 86 to
98 C) brings about a great reduction in numbers, as much as 90 to
99% in some instances. During storage in frozen conditions there is a
steady decrease in number of organisms, but there are at least some
survivors of most kind of organisms after the usual storage periods.

12. • Drying: Dried vegetables and vegetable products are used in dried soups, and
dried species and condiments are used as flavoring material. Many vegetables
can be dried by the process of explosive puffing. Usually small pieces of the diced,
partially dehydrated vegetables are placed in a closed rotating chamber. Heat is
applied, and the chamber is pressurized to a predetermined level; then the
pressure is released instantaneously. This results in an additional loss of water,
but more important, a porous network of capillaries is formed in the product. The
increased porosity simplifies further drying and imparts good reconstituting
ability.
• Use of preservatives: The addition of preservatives to vegetables is not common,
although the surfaces of some vegetables may receive special treatment.
Rutabagas and turnips some times are paraffined to lengthen their keeping time.
Zinc carbonate has been reported to eliminate most mold growth on lettuce,
beets, spinach. Biphenyl vapors will control Fusarium on potatoes. Sodium
chloride is the only added chemical preservatives in common use. There are
added preservatives and developed preservatives which are used.

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