FOODBORNE DISEASES Notes
I. Food preservatives are placed in 3 main categories:
1. Antimicrobials which inhibit growth of bacteria, yeasts/molds and viruses;
2. Antioxidants which slow air oxidation of fats that can lead to rancidity; &
3. Types that block natural ripening & enzymatic processes that continue to occur in foods after harvest.
II. Other commonly used food preservatives & ways foods are preserved:
a. Natural food preservatives comes the salt, sugar, alcohol, vinegar used at home while making pickles, jams and juices etc
b. freezing, boiling, smoking, salting are considered to be the natural ways of preserving food. Coffee powder and soup are
dehydrated and freeze-dried for preservation
c. Sugar and salt are the earliest natural food preservatives that very efficiently drops the growth of bacteria in food. To preserve
meat and fish, salt is still used as a natural food preservative.
d. Chemical preservatives such as: Benzoates (such as sodium benzoate, benzoic acid)
Nitrites (such as sodium nitrite) give red meats their pink hues & prevent Clostridium
botulinum bacteria that spoils meats.
Sulphites (such as sulphur dioxide) keeps fruits freash, & acts as an antimicrobial
Sorbates (such as sodium sorbate, potassium sorbate
e. Artificial preservatives are the chemical substances that stops of delayed the growth of bacteria, spoilage and its discoloration.
Types of Artificial Preservatives Food
a. Antimicrobial agents ; b. Antioxidants; c. Chelating agent
In antimicrobial comes the Benzoates, Sodium benzoate, Sorbates and Nitrites.
Antioxidants include the Sulfites, Vitamin E, Vitamin C and Butylated hydroxytoluene (BHT)
Chelating agent has the Disodium ethylenediaminetetraacetic acid (EDTA), Polyphosphates and Citric acid
f. Some common preservatives and their primary activity
Used in Foods
Insects & Microorganisms
Dried Fruits, Wine, & Juice
Breads, Cakes, Cheeses
Cheeses, Cakes, Salad Dressings
Yeasts & Molds
Soft Drinks, Ketchup, Salad Dressings
h. Osmotic pressure: The principle of osmosis is applied. Foods are preserved by adding salts and sugars to them. These chemicals
remove the water out of microbial cells causing them to shrink. Thus stopping their metabolism. Jams, jellies, fruit syrups, honey etc.
are preserved by high sugar concentration. Fish, meat beef and vegetable products are preserved with salt.
i. Chemical preservatives: The most commonly used are the acids, such as sorbic acid, benzoic acid and propionic acid. These check
mainly the growth of yeasts and molds. Sorbic acid is used for preservation of syrups, salads jellies and some cakes. Benzoic acid is used
Propionic acid is an ingredient of bread and bakery products. Sulphur dioxide, as gas or liquid is also used for dried fruits, molasses
j. Radiation:. UV is used in meat storage facilities which reduce surface contamination, on meat products. Gamma rays are also used
k. Anaerobiosis: Packaging of food products under anaerobic conditions - anaerobiosis is effective in preventing aerobic spoilage
l. Controlled atmospheres: Such atmospheres containing 10% CO2 are used to preserve stored food products as apples and pears. This
III. Some chemicals used as food preservatives that may be hazardous to our health include:
a. Propyl Gallate
This preservative, used to prevent fats and oils from spoiling, might cause cancer. It's used in vegetable oil, meat products, potato
sticks, chicken soup base and chewing gum, and is often used with BHA and BHT (see below).
b. BHA and BHT
Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are used similarly to propyl gallate -- to keep fats and oils from
going rancid. Used commonly in cereals, chewing gum, vegetable oil and potato chips (and also in some food packaging to preserve
freshness), these additives have been found by some studies to cause cancer in rats. If a brand you commonly buy uses these additives,
look for a different variety, as not all manufacturers use these preservatives
c. Potassium Bromate
This additive is used in breads and rolls to increase the volume and produce a fine crumb structure. Although most bromate breaks
down into bromide, which is harmless, the bromate that does remain causes cancer in animals. Bromate has been banned throughout
the world, except for in the United States and Japan. In California, a cancer warning would likely be required if it were used, which is
why it is rarely used in that state.
d. Monosodium glutamate (MSG)
MSG is used as a flavor enhancer in many packaged foods, including soups, salad dressings, sausages, hot dogs, canned tuna, potato
chips and many more. According to Dr. Russell Blaylock, an author and neurosurgeon, there is a link between sudden cardiac death,
particularly in athletes, and excitotoxic damage caused by food additives like MSG and artificial sweeteners. Excitotoxins are, according
to Dr. Blaylock, "A group of excitatory amino acids that can cause sensitive neurons to die."
Many consumers have also personally experienced the ill effects of MSG, which leave them with a headache, nausea or vomiting after
eating MSG-containing foods. To find out more about the side effects associated with MSG, as well as a complete
e. Aspartame (Equal, NutraSweet)
This artificial sweetener is found in Equal and NutraSweet, along with products that contain them (diet sodas and other low-cal and
diet foods). This sweetener has been found to cause brain tumors in rats as far back as the 1970s, however a more recent study in 2005
found that even small doses increase the incidence of lymphomas and leukemia in rats, along with brain tumors. People who are
sensitive to aspartame may also suffer from headaches, dizziness and hallucinations after consuming it.
f. Sodium Nitrite (Sodium Nitrate)
Sodium nitrite (or sodium nitrate) is used as a preservative, coloring and flavoring in bacon, ham,
hot dogs, luncheon meats, corned beef, smoked fish and other processed meats. These additives can
lead to the formation of cancer-causing chemicals called nitrosamines.
Some studies have found a link between consuming cured meats and nitrite and cancer in humans.
Acesulfame-K is an artificial sweetener that's about 200 times sweeter than sugar. It's used in baked
goods, chewing gum, gelatin desserts and soft drinks. Two rat studies have found that this substance
may cause cancer, and other studies to reliably prove this additive's safety have not been conducted.
Acesulfame-K also breaks down into acetoacetamide, which has been found to affect the thyroid in
rats, rabbits and dogs.
Olestra is a fat substitute used in crackers and potato chips, marketed under the brand name Olean.
This synthetic fat is not absorbed by the body (instead it goes right through it), so it can cause
diarrhea, loose stools, abdominal cramps and flatulence, along with other effects. Further, olestra
reduces the body's ability to absorb beneficial fat-soluble nutrients, including lycopene, lutein and
i. Blue 1 and Blue 2
Blue 1, used to color candy, beverages and baked goods, may cause cancer. Blue 2, found in pet
food, candy and beverages, has caused brain tumors in mice.
Like diet soda? The aspartame
that's used to sweeten it
increases lymphomas, leukemia
and brain tumors in rats -- even
in small doses.
j. Red 3
This food coloring is used in cherries (in fruit cocktails), baked goods and candy. It causes thyroid tumors in rats, and may cause them
in humans as well.
k. Yellow 6
As the third most often used food coloring, yellow 6 is found in many products, including backed goods, candy, gelatin and sausages.
It has been found to cause adrenal gland and kidney tumors, and contains small amounts of many carcinogens.
l. Hydrogenated Vegetable Oil
The process used to make hydrogenated vegetable oil (or partially hydrogenated vegetable oil) creates trans fats, which promote heart
disease and diabetes. The Institute of Medicine has advised that consumers should eat as little trans fat as possible. You should avoid
anything with these ingredients on the label, which includes some margarine, vegetable shortening, crackers, cookies, baked goods, salad
dressings, bread and more. It's used because it reduces cost and increases the shelf life and flavor stability of foods.
IV. Some factors that make some foods more sensitive to microbial growth?
b. water content
c. exposure to light
V. 90 percent of the cases of food poisoning each year are caused by the bacteria Staphylococcus aureus, Salmonella, Clostridium
perfringens, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus, Bacillus cereus, and Entero-pathogenic Escherichia coli.
These bacteria are commonly found on many raw foods. Normally a large number of food-poisoning bacteria must be present to cause
illness. Therefore, illness can be prevented by (1) controlling the initial number of bacteria present, (2) preventing the small number
from growing, (3) destroying the bacteria by proper cooking and (4) avoiding re-contamination.
VI. Microorganisms that can cause food poisoning:
a. Staphylococcus aureus,
c. Clostridium perfringens
e. Listeria monocytogenes,
f. Vibrio parahaemolyticus
g. Bacillus cereus
Staphylococcus Produces a
Nose and throat of
30 to 50 percent
skin and superficial
4 to 6 hours.
No growth below
40o F. Bacteria are
destroyed by normal
cooking but toxin is
Intestinal tracts of High protein
animals and man foods - meat;
and fever within
12 to 24 hours.
of cooked foods.
No growth below
40o F. Bacteria are
destroyed by normal
Live cells must
dust, soil and
tracts of animals
12 to 24 hours.
No vomiting or
of hot foods, and
No growth below
40o degrees F.
Bacteria are killed by
normal cooking but
a heat-stable spore
requires a low
Home-canned Blurred vision,
Improper methods of Type E and Type B
can grow at 38o F.
Bacteria destroyed by
cooking and the
toxin is destroyed by
boiling for 5 to 10
minutes. Heatresistant spore can
parahaemolyticus for growth.
Fish and shellfish
soil, dust and
monocytogenes conditions for
and water. Can
survive for long
periods in soil and
sensitive, does and foods of
not grow below animal origin.
Not frequent Poultry, beef,
cause of human swine. Isolated
only in human
Enteropathogenic Can produce
Feces of infected
toxins that are humans.
heat stable and
others that are
Recontamination of No growth below
cooked foods or
40o F. Bacteria killed
eating raw seafood. by normal cooking.
fever within 12
to 24 hours.
Starchy food. Mild case of
within 12 to 24
No growth below
40o F. Bacteria killed
by normal cooking,
spore can survive.
tempertures (161o F.
for 15 seconds.)
Meat, poulty, Diarrhea,
mushrooms. cramps and
abdominal pain, Cross-contamination.
Sensitive to drying
or freezing. Survives
in milk and water at
39 o F for several
F.) Sensitive to heat
Inadequate cooking. Organisms can be
Recontamination of controlled by
heating. Can grow at
Hypertext markup by Gretchen Eagle and Dan Lineberger. Http://aggie-horticulture.tamu.edu/extension/poison.html
6. Staphylococcus produces an heat stable toxin_ that is relatively Harmless.
7. An organism normally found in human intestines that can cause food poisoning is bacillus (Escherichia coli) but its growth is
usually limited by intestinal Flora (Pyer’s Patches).
8. The most severe type of food poisoning is that caused by E. coli O157:H7
9. A food source of infant botulism is __ Clostridium botulinum
10. List 5 common symptoms of food poisoning:
a. Nausea & Vomiting
fever & chills
e. bloody stools
11. How is food poisoning different from food infection?
a. Food infection refers to the presence of bacteria, etc within the food.
b. Food poisoning refers to the effect on the body after ingesting such infected food.
12. Salmonellosis is caused by the organism rod shaped, gram negative Salmonella bacteria.
13. Food poisoning by some organisms is more common in the summer months. especially during summer when food may not be kept
cold enough to prevent bacteria from growing.
14. E. coli food poisoning is caused by the strain __ E. coli strain O157:H7 ___. Two serious consequences of this is severe bloody
diarrhea & abdominal cramps and ___Neausea & vomiting to death_____________.
16. Travelers to developing countries have a high incidence of enteric infections due to contaminated water. The three microorganisms
which are the causative agents are __Bacteria__________, __yeast/fungi______________, & ___parasites___________.
17. Campylobacter can grow in a reduced oxygen tension which makes it a sensitive to drying or freezing, but they can survive in the
environment in cold ground-water, soil, and in refrigerated food for weeks.
18. The two species of Campylobacter implicated in food poisoning is Campylobacter jejuni _ & _ Campylobacter fetus
19. Listeriosis is caused by the microorganism bacterium Listeria monocytogenes It is unique in that in can grow at ___a wide range
of___temperatures which is ____4___ Celsius or ___107____ degrees Fahrenheit.
20. The mortality rate for botulism is ____8________% and for Listeriosis it is __25__________%.
21. The microorganism that has been implicated as a source of peptic ulcer disease is flagellated corkscrew-shaped bacterium,
Helicobacter pylori which can be treated with the use of antibiotics.
22. Hepatitis A virus is transmitted by _feces__& contaminated water____________ while Hepatitis B is primarily transmitted by
______direct contact w/blood________, __body fluids__________, or ___sexual contact________. Hepatitis A is one of
the least threatening forms of the disease.
23. Hepatitis C is spread by ___ contact with infected blood ________________ &___blood transfusions______________.
24. Serious complications from hepatitis include ___liver disease____________ & _____death_________.
25. other strains of the hepatitis virus are
Hepatitis D is a particularly odd strain of hepatitis. For the disease to be present in the body, the individual must already be afflicted
with hepatitis B, as the disease alters the genome in a way that allows hepatitis D to exist.
Hepatitis E is a strain that is much like that of hepatitis A. This type of the disease most commonly occurs in India and its
Hepatitis G, the latest type of hepatitis that has been discovered and little is known about the disease so far.
15. List 4 methods of food preservation:
Effect on microbial growth or survival
Low temperature to retard growth
Low temperature and reduction of water activity prevents microbial
growth, slowing of oxidation reactions
Reduction in water activity sufficient to delay or prevent microbial
Drying, curing and conserving
Low oxygen tension inhibits strict aerobes and delays growth of
Vacuum and oxygen free modified atmosphere packaging
Carbon dioxide enriched and or modified atmosphere
Specific inhibition of some micro-organisms
Addition of weak acids; e.g. sodium lactate
Reduction of the intracellular pH of micro-organisms
Reduction of pH value in situ by microbial action and sometimes
Addition of preservatives such as nitrite or sulphite ions
Pasteurization and appertization
Food irradiation (Radurization, radicidation and
Application of high hydrostatic pressure (Pascalization)
Pulsed electric field processing (PEF treatment9)
additional inhibition by the lactic and acetic acids formed and by other
microbial products. (e.g. ethanol, bacteriocins)
Cooking in high sucrose concentration creating too high osmotic
pressure for most microbial survival.
Steeping or cooking in Ethanol produces toxic inhibition of microbes.
Can be combined with sugar preservation
Compartmentalisation and nutrient limitation within the aqueous
droplets in water-in-oil emulsion foods
Inhibition of specific groups of micro-organisms
Delivery of heat sufficient to inactivate target micro-organisms to the
Delivery of ionising radiation to disrupt cellular RNA
Pressure-inactivation of vegetative bacteria, yeasts and moulds
Short bursts of electricity for microbial inactivation
26. Several foods that can be sources of many types of food poisoning include meat & dairy products, and produce. Certain
microorganisms are commonly associated with certain foods.
Match the following food with the most likely pathogen.
1. canned vegetables & sushi
a. E. coli
2. creamy salad dressings
3. ground beef
4. processed meat
5. uncooked eggs/turkey
f. Clostridium botulinum