Download 02_Food Safety Hazards

Food Safety Hazards
Micro-organisms that affect food safety
Our Goal
To help you understand what micro-organisms are
and how they affect food so that you learn how to
keep food safe.
Learning Objectives
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Define a micro-organism;
Understand their effects on food and people;
Identify different types of micro-organisms; and
Understand how they cause illness.
What is a micro-organism?
• Micro means tiny
• Organism means living
creature
• Micro-organisms are so
small you can’t see them
without a microscope.
Effects of Micro-organisms
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Inert
Beneficial
Spoilage
Pathogens
Types of Micro-organisms
Micro-organisms can be grouped as:
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Bacteria
Viruses
Parasites
Protozoa
Fungi – yeasts and moulds
Prions
Bacteria
• They are found all around us.
• There are typically 40 million bacterial cells in a gram of
soil and a million bacterial cells in a millilitre of fresh
water!
• Bacteria are the most common cause of foodborne
illness.
Bacterial Growth
• Grow by cell division.
• Can double in numbers every 10 to 20 minutes
• After four hours, 20 bacteria can become
1,310,720 bacteria!
• This video shows e.coli bacteria multiplying.
Effect of Temperature
• Some bacterial toxins are not destroyed by heat.
• Cooking bacteria to a high enough temperature
for a period of time will kill or inactivate them.
• Keep bacteria out of the temperature danger
zone, to minimize their growth.
Bacterial Toxins
• Some bacteria excrete toxins.
• Toxins can make you sick even after the bacteria have
died.
• Symptoms can appear from 1 to 6 hours.
• Examples include:
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Clostridium botulinum
Clostridium perfringens
Staphylococcus aureus
Bacillus cereus
• Resistant to high heat
Spores
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A protective ‘shell’.
Helps bacteria survive in poor conditions.
Some bacteria go dormant (not killed) during cooking.
Bacteria resume multiplication once back in the TDZ.
FATTOM
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Food
Acidity
Temperature
Time
Oxygen
Moisture
Food
• Most micro-organisms require food to live.
• Bacteria like proteins, but can grow on Cooked
Vegetables, Rice, Baked Potatoes, Sliced Melons,
Sprouts, Garlic & Oil as well.
• Food you purchase will have bacteria on it when you
receive it.
• That is why food handling is so important to eliminate
dangerous germs.
Acidity
Temperature
Time
Oxygen
• Aerobic - needs oxygen
• Anaerobic - grows in the absence of oxygen
• Facultative - can grow with or without oxygen
Moisture
• High moisture content (‘available water’) helps bacteria
growth.
• Available water (aw) is measured on a scale of 0 to 1.0.
• Most potentially hazardous foods have 0.86 or higher.
• Examples include meat, fish, poultry, dairy, fruits and
vegetables .
• Drying foods can lower the risk of bacterial
multiplication.
• Adding water to dried foods supports bacterial growth.
Controlling Growth
• Some environmental factors help
minimize growth.
• Increased acidity and lowering
moisture helps; but
• The best control is reduced time
in the temperature danger zone.
Viruses
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The smallest of the microorganisms
Can resist hot and cold temperatures
Often the cause of foodborne illness
Don’t multiply in food but can be carried on food
People eat the food become infected
Examples of viruses commonly transmitted in food:
• Norovirus (also called Norwalk virus)
• Rotavirus
• Hepatitis A & E
Viral Reproduction
• A virus (shown in blue) lands on
a human cell and injects its
DNA
• Viruses use the cell’s DNA to
make viral DNA
• The viral DNA makes more
viruses
• Eventually the cell wall bursts
sending out viruses to infect
other cells
• Viruses can multiply even
faster than bacteria in this
manner
Parasites
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Need a host to survive
Very difficult to get rid of once one is in your body
Can be single or multi-celled
Can come from a number of sources, including:
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meat,
seafood,
water,
infected food handlers
Types of Parasites
Common parasites in food include:
• Anisakis from infected fish (see
picture) used for sushi and
sashimi
• Trichinella from infected meat
usually from wild game and pork
• Cooking to 70 °C(158 °F) will kill
the parasites
• Freezing to −20 °C (−4 °F) for 7
or more days will kill Anisakis
larvae
Protozoa
• These are single cell organisms
• Most are too small to see without microscope
• They are found in water, soil and in food contaminated
by food handlers
• Boiling water will eliminate them
• Good hygiene including proper hand washing will help
prevent infections
Types of Protozoa
Common Protozoa:
• Giardia lamblia (left) is a
frequent cause if infection from
contaminated water
• Cryptosporidium also found in
water supplies
• Cyclospora cayetanensis found
in contaminated water used to
water crops (cases include
imported raspberries)
• Toxoplasma found in cats and
dangerous to pregnant women
and infants
Fungi
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This includes moulds and yeasts
Often can be seen as fuzzy patches on food
Moulds prefer moist environments
Can grow at refrigerated temperatures
Require oxygen to grow
Some produce toxins that can contaminate food
Toxins can penetrate foods to a depth of 5 cm or 2
inches (deeper in soft cheeses and liquids)
• Remove at least 5 cm (2 inches) of food that has mould
• It is highly recommended to discard food with mould
Mould Growth
Fruiting body
Spores
Food
Toxin producing
filaments in food
Prions
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Smaller than viruses
Made up only of protein
“Mad cow disease” is believed to be caused by prions
Creutzfeldt-Jacob disease (CJD) may be a human
version of this fatal disease caused by eating beef from
infected cattle
• Special laws in Canada have been put into place to
help prevent cattle from becoming infected
• It is important to purchase beef products from approved
(government inspected) suppliers
How Micro-organisms
Make Us Sick
• A ‘foodborne infection’ – happens when food with
living bacteria is eaten.
• A ‘foodborne intoxication’ (sometimes called food
poisoning) happens when the food contains toxins
produced by bacteria.
• A ‘toxin-mediated infection’ happens when the food
that is eaten has living bacteria on it and these bacteria
also produce toxins.
Summary
 A micro-organism is a tiny living creature
 Examples include bacteria, viruses, parasites,
protozoa, and fungi
 These organisms can contaminate food making it
unsafe to eat
 If the micro-organisms, or toxins they may produce, are
consumed people can become very sick & even die
Quiz