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Who
is FAT TOM?
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FAT TOM
is a term that in
short explains what encourages
foodborne pathogens to grow.
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F
is for Food
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Nutrients available
in food often determine which microorganisms will
grow in it. While some microorganisms have simple
nutrient requirements, some pathogens require
a complex diet, including vitamins and minerals
found in the foods we eat.
Moist protein-rich
foods, such as meat, milk, eggs and fish, are
potentially hazardous. That is, they are
most likely to cause foodborne illness because
they are vehicles of transmission of pathogenic
bacteria and can support growth of these bacteria.
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A
is for Acidity
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- Bacteria grow
best in an environment that is neutral or slightly
acidic. Most bacterial growth is inhibited in
very acidic conditions. That is why acidic foods,
like vinegar and fresh fruits (especially citrus),
seldom provide a favorable climate for pathogenic
bacteria.
- pH is the symbol
for the degree of acidity or alkalinity (base)
of a substance.
- pH is measured
on a scale from 0 to 14.0. An environment with
a pH of 7.0 is exactly neutral--neither acid
nor alkaline. Foods with a pH below 7.0 are
acidic; pH above 7.0 is alkaline. The lower
the pH, the higher the acidity; the higher the
pH, the lower the acidity. Most bacteria will
not grow at pH levels below 4.6.
Microorganisms thrive in a pH range between
6.6 and 7.5.
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T
is for Time
(Also known as the two-hour rule.)
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Pathogenic
microorganisms reproduce by cell division. One becomes
two. Two become four. When small numbers of pathogens
are present in food, they pose a very low risk to
consumers. However, when low acid food (food with
a neutral or alkaline pH) is abused by placing it
in the DANGER ZONE
(5° to 60°C) longer than two
hours, pathogens multiply rapidly. Restricting
the time that low acid foods stay in the
DANGER ZONE
to two hours or less prevents growth
of large numbers of pathogens. |
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T
is for Temperature
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Microorganisms
grow fast between the temperatures of
5°
and 60°C.
One
important rule of food safety is to stay
out of the DANGER
ZONE, where potentially
hazardous foods support the growth of pathogenic
microorganisms.
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0
is for Oxygen
(Air)
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Some microorganisms
need oxygen
(air) to grow, that is, they are aerobic.
When foods
such as meat or vegetables are canned, oxygen
is excluded from the environment. Therefore, growth
of aerobic organisms is controlled and the food
is preserved. Such foods are shelf stable and
do not require refrigeration.
However, some microorganisms
will grow only in anaerobic conditions
(in the absence of oxygen). Botulism, a rare type
of foodborne illness, is caused by a specific
type of organism that grows only in anaerobic
conditions (in the absence of oxygen).
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M
is for Moisture |
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All microorganisms
must have an abundant supply of water to grow.
Consequently, perishability of a food is related
not only to moisture content, but also to water
activity.
Moisture content
is the amount of water in food and is expressed
as a percentage. Water activity ( aw
) is the amount of water available for deterioration
reactions and is measured on a scale of 0 to 1.0.
Bacteria, yeast, and mold multiply rapidly at
a high water activity--above 0.86. Meat, produce
and soft cheeses have aw in this range
(between 0.86 and 1.0).
Pathogenic bacteria
have difficulty growing in foods such as jams
and jellies, flours, etc. where aw
is below 0.85. Foods preserved with salt or sugar,
such as jams and jellies have a lower aw
because salt and sugar deprive microorganisms
of water and inhibit their reproduction.
These products are shelf-stable (i.e. they do
not need refrigeration).
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