38 ◾ Fundamental Food Microbiology
Miscellaneous
Foods might be contaminated with microorganisms from several other sources, namely packaging
and wrapping materials, containers, flies, vermin, birds, house pets, and rodents. Many types of
packaging materials are used in food. Because they are used in products ready for consumption
and, in some cases, without further heating, proper microbiological standards (or specifications)
for packaging materials are necessary. Any failure to produce microbiologically acceptable products can reduce the quality of food. Flies, vermin, birds, and rodents in food processing and food
preparation and storage facilities should be viewed with concern as they can carry pathogenic
microorganisms. House pets can also harbor pathogens; proper care should be taken not to contaminate food from these source.
Conclusion
Microorganisms enter foods from both internal and external sources. Their levels and types
depend on the care used during production, processing, and storage of foods. Recontaminations
of heat-processed foods with pathogens have been associated with many foodborne disease outbreaks. Proper sanitation at every stage helps reduce the microbial level normally expected in a
food. Normal microbiological quality of foods is discussed in Chapter 4.
QUESTIONS
1. Briefly discuss how an understanding of the microbial sources in food can be helpful to a
food microbiologist.
2. List five major sources of foodborne pathogens in foods and indicate the measures that
should be implemented to reduce their incidence in foods.
3. A Salmonella outbreak from the consumption of a national brand of ice cream, involving
more than 50,000 consumers, was found to be related to contamination of heat-treated ice
cream mix with raw liquid egg containing the pathogen. Both products were transported by
the same truck at different times. Briefly indicate how this could have been avoided.
4. A batch of turkey rolls (10 lb—approximately 4.5 Kg—each) were cooked to 165°F internal
temperature in bags, opened, sliced, vacuum-packaged, and stored at 40°F. The product was
expected to have a refrigerated shelf life of 50 days. However, after 40 days, the packages
contained gas and approximately 10 7 bacterial cells/g of meat. The bacterial species involved
in the spoilage was found to be Leuconostoc carnosum, which is killed at 165°F. What could
be the sources of the bacterial species in this cooked product?
5. Consumption of vacuum-packaged refrigerated hotdogs has been frequently incriminated
with listeriosis although the internal temperature used for cooking the raw products (160°F)
is high enough to kill the pathogen. Discuss the possible sources of the pathogen in the
cooked products.
6. A child consumed watermelon in a restaurant and was thereafter infected with Esc. coli
O157:H7. Investigations revealed that the knife used to slice the melon was also used to cut
raw beef (and then washed). What could have been done to prevent the situation?
Miscellaneous
Foods might be contaminated with microorganisms from several other sources, namely packaging
and wrapping materials, containers, flies, vermin, birds, house pets, and rodents. Many types of
packaging materials are used in food. Because they are used in products ready for consumption
and, in some cases, without further heating, proper microbiological standards (or specifications)
for packaging materials are necessary. Any failure to produce microbiologically acceptable products can reduce the quality of food. Flies, vermin, birds, and rodents in food processing and food
preparation and storage facilities should be viewed with concern as they can carry pathogenic
microorganisms. House pets can also harbor pathogens; proper care should be taken not to contaminate food from these source.
Conclusion
Microorganisms enter foods from both internal and external sources. Their levels and types
depend on the care used during production, processing, and storage of foods. Recontaminations
of heat-processed foods with pathogens have been associated with many foodborne disease outbreaks. Proper sanitation at every stage helps reduce the microbial level normally expected in a
food. Normal microbiological quality of foods is discussed in Chapter 4.
QUESTIONS
1. Briefly discuss how an understanding of the microbial sources in food can be helpful to a
food microbiologist.
2. List five major sources of foodborne pathogens in foods and indicate the measures that
should be implemented to reduce their incidence in foods.
3. A Salmonella outbreak from the consumption of a national brand of ice cream, involving
more than 50,000 consumers, was found to be related to contamination of heat-treated ice
cream mix with raw liquid egg containing the pathogen. Both products were transported by
the same truck at different times. Briefly indicate how this could have been avoided.
4. A batch of turkey rolls (10 lb—approximately 4.5 Kg—each) were cooked to 165°F internal
temperature in bags, opened, sliced, vacuum-packaged, and stored at 40°F. The product was
expected to have a refrigerated shelf life of 50 days. However, after 40 days, the packages
contained gas and approximately 10 7 bacterial cells/g of meat. The bacterial species involved
in the spoilage was found to be Leuconostoc carnosum, which is killed at 165°F. What could
be the sources of the bacterial species in this cooked product?
5. Consumption of vacuum-packaged refrigerated hotdogs has been frequently incriminated
with listeriosis although the internal temperature used for cooking the raw products (160°F)
is high enough to kill the pathogen. Discuss the possible sources of the pathogen in the
cooked products.
6. A child consumed watermelon in a restaurant and was thereafter infected with Esc. coli
O157:H7. Investigations revealed that the knife used to slice the melon was also used to cut
raw beef (and then washed). What could have been done to prevent the situation?