7/31/2019 Food Hygiene Notes
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Cross-contamination: it is the transfer of micro-organisms
between food, surfaces and
equipments. This is of particular concern to high-risk
foods*(protein rich moist foods and
ready to eat foods can get contaminated easily by pathogenic
bacteria). Cross contamination
can occur directly between foods or indirectly through something
else. For eg:-
1) Where raw food and ready to eat foods come into direct
contact with each other.2) Knives and chopping boards are used for
raw foods and then for ready to eat foods
without first washing them.
3) Hands not washed between using raw foods and ready to eat
foods.4) Dirty hands wiped on clothing.5) Clothes not sanitised
after wiping them on dirty surfaces.
Cross contamination is the result of carelessness and not
following of proper procedures. For
eg: using the same knives and chopping boards for both raw and
cooked food without
washing.
Avoiding cross contamination:
1) Creating barriers of good design and proper layout of
premises.2) Keep the handling of raw and ready to eat foods
separate.(eg .separate refrigeration
units for cooked and raw foods,
3) Using separate utensils and equipments.4) Always store ready
to eat foods away from or above raw foods(e.g. storing cooked
food above raw food in a refrigeration unit)
5) Effective and thorough hand-washing.6) Effective cleaning and
disinfection of mops, cloths, equipments and work surfaces.7)
Cleaning the high-risk food area before the raw food area.
Using colour-coded knives and chopping boards for raw and cooked
food is a good way to
prevent cross-contamination.(red for raw meat and yellow for
cooked meat)
Ways to prevent microbiological contamination: 1) prevent
contamination and cross-
contamination, 2) slow down or prevent multiplication of
bacteria, 3) destroy harmful
bacteria.
Heat food until piping hot3)
Store food at 5 degree Celsius or below2)
Cover cuts and sores-1)
Washing hands between handling raw and cooked food1)
Cook chicken thoroughly- 3)
Store frozen food at -18 degree Celsius : 2)
7/31/2019 Food Hygiene Notes
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Microorganisms are tiny living creatures found everywhere. Most
are harmless, some are
useful, some can cause spoilage in food and drink making it
unfit for consumption.
Those microorganisms that cause food borne illness are called as
pathogens(disease causing
microbes).
Bacteria growth: Bacteria are simple, single-celled organisms
which under favourable
conditions can grow and divide into two identical cells.
In ideal conditions, this will occur every 10-20 min depending
upon the bacteria. Ideally most
pathogens require a moist, low acid and protein rich food at a
temperature of about 37 degree
Celsius.
Factors for bacteria growthThere are certain factors that are
required for bacteria to grow
and survive such as :-
1) Food: Bacteria need food to grow and survive. The acidity of
the food will determinethe level of their growth. Salt and
preservatives can inhibit the growth of bacteria in
food (i.e., slow down or prevent). Pathogens need protein rich
foods to grow. These
are also called as High-risk Foods(for e.g.: cooked meats,
cooked poultry, as well
as cooked , lightly cooked or raw egg dishes, dairy products,
salads and cooked rice).
Any food that is consumed without much or further cooking is
considered to be high-
risk. Also, the greater the preparation and handling of a food
product the more are the
chances of it being contaminated. Hence, diced ham is more
likely to be contaminated
than a slice of ham .
2) Moisture : All living things require water to survive.
Bacteria take their water frommoist foods or wet surfaces but they
do not require much moisture, so for eg.: centre
of a pie or a chicken leg is sufficient. Moreover, the moisture
needs to be in a form the
micro-organism can use so salty solutions such as brine will
hinder the growth of
bacteria. Also, drying of food is a good solution.
3) Presence or absence of oxygen: Human beings need oxygen to
survive. This is truefor some bacteria and not for others. The
growth of both types can be curbed by
packing the food in other gases. Some bacteria need oxygen for
survival and need
exposure to air. Others grow well in the absence of oxygen;
hence care has to be taken
with vacuum-packed products. Controlled
atmosphere-packaginginvolves foodbeing packed in nitrogen or carbon
dioxide which slows down the growth of bacteria.
These foods have a longer shelf-life.
4) Temperature: Temperature can help to control the growth of
bacteria. At hightemperatures, bacteria can be killed while at low
temperatures, bacteria can be
stopped from multiplying or their speed of growth can be slowed
down. Below 5
degree Celsius, pathogens become inactive and stop multiplying.
They do not die, and
as soon as temperature rises, they start multiplying again.
Pathogens grow best at
human body temperature(i.e.,37 degree Celsius). Above 63 degree
Celsius, all
pathogens will begin to die off. At the centre of food, if a
temperature of 75 degree
Celsius is reached, all normal living cells of pathogens will
die for 30 seconds.
