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Family and LifeStyle
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July 2009
Contents
Page
8 Food Hygiene
8.1 Food Hygiene
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8.2 Personal Hygiene
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8.2.1 Personal Hygiene Practices
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8.2.2 Hygiene Practices for Food Preparation
and Serving
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8.3 Environmental Hygiene
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8.4 Storage of Food
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8.4.1 Dry food stores
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8.4.2 Refrigerators
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8.4.3 Deep-freeze storage
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8.5 Safe Practices in Defrosting (thawing)
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8.5.1 Defrosting by refrigerator
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8.5.2 Defrosting under running water
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8.5.3 Defrosting by microwave oven
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8 Food Hygiene
The hot and humid climate of summer in Hong Kong provides a perfect environment
for bacteria to multiply. Consumption of contaminated food or water can result in food
poisoning or other food borne-disease such as cholera or Hepatitis A. It’s therefore
important to pay attention to personal, food and environmental hygiene.
8.1 Food hygiene
Purchase of food
❖ Purchase food from a hygienic, reliable and reputable source to ensure quality.
Never patronize unlicensed hawkers.
❖ Choose fresh meat and vegetables. Meat should have a fresh red colour and luster
and should have an elastic feel. Vegetables should have a fresh green colour with
no rotting leaves. Shellfish should have intact shells. The water and containers
rearing shellfish should be clean.
❖ Avoid stocking up large amounts of food.
❖ Check expiry dates of pre-packaged foods, e.g. “use by” date and “best before”
date. Do not buy expired food or those with damaged package.
❖ Do not purchase food with abnormal appearance such as rusty canned foods, any
change of colour or foul smell.
❖ Do not buy any food that is not covered properly e.g. barbecued meat hanging
outside the shops. Avoid buying non-prepacked drinks and fruits that have already
been cut or peeled.
Handling of food
❖ Food that spoils easily or will not be cooked immediately should be stored in the
refrigerator.
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❖ Raw and cooked foods should be stored separately. Raw food should be stored on
the lower shelf of the refrigerator, and cooked food on the upper shelf.
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❖ Keep your refrigerator’s temperature below 4℃. Do not store excessive amount of
food in the refrigerator, as this will affect the circulation of cold air.
❖ Keep your refrigerator clean.
❖ Always wash your hands with soap and water before preparing food and after
handling raw meat.
❖ Do not handle food when suffering from diarrhoea or some other gastro-intestinal
illness.
Cooking of food
❖ All meat, seafood and vegetables must be washed thoroughly. Remove all internal
organs from fish. Scrub the shells of shellfish, and then soak them in clean water for
a period of time. Remove the outer leaves of vegetables, and soak the vegetables
in clean water for a period of time.
❖ To avoid cross-contamination, use different sets of knives and chopping boards for
raw and cooked foods. If only one set of knife and chopping board is available, use it
for cooked food first. Brush and wash the used utensils with detergent immediately
after use.
❖ Cook food thoroughly. Frozen food should be completely defrosted before cooking,
and preferably should be cut into thin slices to facilitate thorough cooking.
❖ Eat your cooked food as soon as possible after cooking. In the case of cold dishes
such as salads and jellyfish, keep them in the refrigerator right until they are ready
to be served.
❖ Cook only as much food as you can eat to avoid leftovers. If there is leftover, wrap
it well before storing in the refrigerator. Reheat food thoroughly before serving.
Storage of food
❖ Store raw and cooked foods separately in the refrigerator (cooked food in the upper
shelf and raw food in the lower shelf) to avoid cross-contamination.
❖ Frozen food must be completely defrosted before cooking and should be cooked
thoroughly. Defrost the frozen food either by placing it in the lower shelf of
refrigerator or thawing it under running water. Do not leave frozen food in room
temperature to avoid rapid growth of bacteria.
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❖ Never leave food, raw or cooked, at room temperature for more than 2 hours.
Serve cooked food as soon as possible after cooking. Leftovers should be kept in
the refrigerator at 4°C or below.
❖ Do not store excessive amount of food in the refrigerator, as this will affect the
circulation of cold air.
❖ All foods as well as condiments should be covered and stored properly.
8.2 Personal hygiene
Personal hygiene is aimed at preventing the spread of bacteria from the body or
clothing to avoid food poisoning. It is the responsibility of the individual and all food
handlers to understand the principles of food hygiene and its importance.
❖ to prevent food becoming contaminated with food poisoning bacteria;
❖ to prevent the multiplication of any food poisoning bacteria which get into food;
❖ to destroy any food poisoning bacteria which may be present by thorough cooking.
8.2.1 Personal Hygiene Practices
(A) Clothing and Personal Effects
(i) Only clean and protective clothing should be worn and they should be fit to wear.
If they become soiled during food preparation, they should be changed or cleaned
as necessary. These clothing should be washed after use.
(ii) Wear disposable gloves when handling ready-to-eat food. They should be
discarded if damaged or soiled.
(iii) Wear face masks when handling food. They should be discarded when damaged,
soiled, or after prolonged use.
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(iv) Shoes should be worn when handling food.
(v) Personal belonging, such as handbags, footwear, umbrellas and dirty clothing,
should not be stored or left in any food preparation area. They should be put away
from food preparation areas.
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(B) Hair
(i) During the handling food, hair should be covered with a clean hat or hair net. Long
hair should be tied back as well.
(ii) Combing of hair should not be conducted in food handling areas.
(C) Nails and Jewelry
(i) Long and dirty nails harbour dirt and bacteria, therefore, nails should be kept short
and unpolished.
(ii) Food handlers should have their watches, rings and jewelry removed before
they work with food. Jewelry which may easily become detached should not
be worn while handling food to avoid them from falling on the food and cause
contamination.
(D) Hands
Hands of food handlers should be kept clean at all times.
(i) Cuts or wounds on hands of food handlers should be completely covered by
suitable waterproof dressings or gloves.
(ii) Food handlers should wash their hands:
❖
❖
❖
❖
❖
❖
❖
❖
❖
before commencing work;
before handling food;
after visiting the toilet;
after handling raw food;
after handling soiled equipment or utensils;
after coughing, sneezing, smoking, eating, drinking or blowing nose;
after handling animals or waste;
after touching their ears, noses, hair, mouths or other parts of their bodies; or
after engaging in any activities that may contaminate hands. (e.g. handling
money, carrying out cleaning duties, etc.)
(iii) Staff engaged in food handling should not be allowed to handle cash
simultaneously.
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(iv) Handwashing should be frequent, thorough and performed in basins. The following
proper procedures should be adopted for washing hands:
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❖ wet the hands with running water, preferably with warm water;
❖ apply liquid soap;
❖ rub hands for 20 seconds (wash all surfaces thoroughly, including forearms,
wrists, palms, back of hands, fingers and under fingernails);
❖ if necessary, use a clean and sanitary nail brush to clean nails;
❖ rinse hands thoroughly;
❖ dry hands with a clean paper towel, continuous cloth towel in dispenser or air
dryer.
(E) Health
(i) Any person engaged in handling food who suffers from diarrhoea, vomiting, septic
cuts, boils or discharges from the ear, eye or nose should not come into contact
with food, food utensils and equipment.
(ii) When sneezing or coughing inside food preparation area is unavoidable, food
handlers should turn away from food and cover their noses and mouths with tissue
paper or handkerchieves. Disposable paper tissues are preferable as they can be
discarded. Hands should then be thoroughly cleaned at once.
(iii) Food handlers with open cuts or wounds on the exposed parts of their bodies
should not be allowed to handle food or to come into contact with food utensils,
equipment, unless such cuts / wounds are completely protected by impermeable
or waterproof gloves or dressings. Bandages or dressings should be brightly
coloured so that, if they are inadvertently removed, they will be readily visible if
it falls into food. Bandages and dressings should be changed regularly. A wellequipped first-aid box containing bandages or dressings and antiseptic, should be
kept on the premises.
(F) Personal behaviour
Inside food preparation areas, food handlers should refrain from performing the
following behaviours which may result in contamination of food:
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(i) smoking or using tobacco;
(ii) spitting;
(iii) chewing, eating, sneezing or coughing over unprotected food;
(iv) touching ready-to-eat food with bare hands;
(v) sitting, lying or standing on any surface liable to come into contact with food;
(vi) tasting food with fingers; and
(vii) touching hair or other parts of bodies such as noses, eyes or ears.
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8.2.2 Hygiene Practices for Food Preparation and Serving
(A) It is essential to prevent the contamination of food by bacteria carried by food
handlers or by bacteria from raw foods. The direct handling of food should be
avoided where possible. Food should be handled with utensils, such as tongs.
Food handlers should wear disposable plastic gloves when handling high risk
foods, such as cooked meats.
(B) In the kitchen it is essential to keep raw and cooked foods separated in order
to prevent cross-contamination from raw to cooked foods. This means having
separate preparation areas for the these types of food. Raw food has more bacteria
than cooked food, and are very likely to contain food poisoning bacteria. Separate
equipment should be used for the preparation of raw and cooked foods. Items
such as knives and chopping boards can be colour-coded for different uses, e.g.
for raw meat, raw vegetables, cooked foods. Equipment such as meats slicers
and mincers, which cannot be duplicated, should be thoroughly cleaned after
being used for raw meat.
(C) It is essential to control the temperature of food during preparation, processing,
cooking and storage in order to prevent the multiplication of pathogenic bacteria.
Appropriate temperature control is probably the single most important factor in the
prevention of food poisoning. A breakdown in temperature control is a major factor
in at least 75% of food poisoning outbreaks.
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Figure 8.1 Shows the exponential growth curve of a bacteria. The life cycle of a
typical bacterial cell is 20 minutes. Therefore, the number of bacteria will
be doubled in 20 minutes.
Figure 8.2 A typical growth curve of bacteria.
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(D) Food handlers must avoid keeping high risk foods, such as meats and poultry, egg
and milk dishes, cream cakes and desserts, in the danger zone (5-63℃) for longer
than necessary. Consideration should be given to the following processes:
(i) Preparation: Food should be kept in preparation areas within the shortest period
of time. Preparation areas should be well ventilated and not too hot.
When preparation is finished, food should be cooked, refrigerated
or frozen.
(ii) Defrosting: Frozen foods, must be defrosted before cooking. This should be
carried out at a low temperature, i.e. in a refrigerator, or quickly, e.g.
in microwave oven. Care is needed to ensure that food is completely
defrosted before cooking. Otherwise, at the end of the cooking time,
the centre of the food may not be hot enough to kill bacteria.
(iii) Cooking: Foods, particularly meat and poultry, should be cooked thoroughly,
so that the centre temperature is 70℃, i.e. high enough to kill most
bacteria. This is particularly important for products such as burgers
and sausages. Stews and gravies should be heated to the boiling point
(100℃). Centre temperatures can be checked using a temperature
probe. This must be cleaned between use for different products. After
cooking, food must be served immediately, kept hot or cooled quickly.
(iv) Warm-holding: Food should be kept hot at 70℃ or above in hot cabinets or bainmaries.
(v) Chilling: Cooked foods should be cooled quickly within 1.5 hours. They are best
chilled at temperature of 10℃ or below.
(vi) Reheating: Food should be heated up quickly and heated thoroughly. Small
portions may be heated in a microwave oven, though care is needed
to ensure even cooking and the absence of ‘cold spot’.
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Additional Information
Temperature control during preparation and serving of food
Bacterial growth is the division of one bacterium into two identical daughter cells
during a process called binary fission. Hence, local doubling of the bacterial
population occurs. Both daughter cells from the division do not necessarily
survive. However, if the number surviving exceeds unity on average, the bacterial
population undergoes exponential growth.
Bacterial growth in batch culture can be modeled with four different phases:
lag phase (A), exponential or log phase (B), stationary phase (C), and death
phase (D).
1. During the lag phase, bacteria adapt themselves to growth conditions. It is
the period where the individual bacteria is maturing and not yet able to divide.
During the lag phase of the bacterial growth cycle, synthesis of Ribonucleis
acid (RNA), enzymes and other molecules occur.
2. Exponential phase (sometimes called the log phase) is a period characterised
by cell doubling. The number of new bacteria appearing per unit time is
proportional to the present population. If growth is not limited, doubling
will continue at a constant rate so both the number of cells and the rate of
population increase doubles with each consecutive time period. For this type
of exponential growth, plotting the natural logarithm of cell number against time
producing a straight line. The slope of this line is the specific growth rate of the
organism, which is a measure of the number of divisions per cell per unit time.
The actual rate of this growth (i.e. the slope of the line in the figure) depends
upon the growth conditions, which affect the frequency of cell division events
and the probability of both daughter cells surviving. Exponential growth cannot
continue indefinitely, because the medium is soon depleted of nutrients and
accumulated with wastes.
3. During the stationary phase, the growth rate slows down as a result of nutrient
depletion and accumulation of toxic products. This phase is reached as the
bacteria begin to exhaust the resources that are available to them.
4. At the death phase, bacteria run out of nutrients and die.
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8.3 Environmental hygiene
❖ Maintain good lighting and ventilation in the kitchen. Keep the floor, ceiling and
walls clean and dry.
❖ Ensure good maintenance of refrigerator, cooker hood, exhaust fans and cooking
utensils. The inside of refrigerators including their rims should be cleaned regularly.
Over-frosted refrigerators should be defrosted promptly.
❖ Linens should be used for one single purpose only. For example, towels used for
cleaning up food spills on table surfaces should not be used for any other purpose such
as for polishing dried utensils. Soiled linens should be kept in suitable receptacles
or laundry bags away from food preparation areas to prevent contamination of
food, food equipment and utensils.
❖ Ensure drains are not blocked.
❖ Maintain pest control to eliminate mice, houseflies and cockroaches. Do not keep
pets in the kitchen.
❖ Dispose refuse and food waste into garbage bin with lid on at all times and empty
the contents at least once a day.
❖ Clean food containers immediately after use and store them in a dust and pest-free
cupboard after drying.
8.4 Storage of food
To prevent contamination, food should be stored in suitable containers and kept in
clean conditions.
8.4.1 Dry food stores
(A) Dried foods should be stored in air-tight containers in a cool storage area.
(B) Containers should be stored on racks at least 45cm from the floor to allow circulation
of air.
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8.4.2 Refrigerators
(A) Refrigerators can be used for the short-term storage of a wide variety of foods.
(B) Since most pathogenic bacteria are unable to multiply at 1-4℃, food storage in a
refrigerator is reasonably safe. However, the refrigerated temperature should not
exceed 4℃ as some bacteria (e.g. Listeria monocytogenes) can grow and multiply
at temperature just above this. Many microorganisms can grow fairly well at low
temperatures and spoilage will eventually occur, even within a refrigerator.
(C)For a refrigerator to function efficiently, air must be able to circulate freely around
the food. Therefore, refrigerators should not be overloaded.
(D)Raw foods should be well separated from cooked foods to prevent crosscontamination by food poisoning bacteria. If they are stored in the refrigerator,
cooked foods should be above raw foods.
(E) Strong smelling foods should be stored in air-tight containers.
(F) Refrigerators with automatic defrosting are recommended, as they keep the ice
layer inside the refrigerator to a minimum. For other refrigerators, defrosting must
be carried out at regular intervals.
8.4.3 Deep-freeze storage
(A) Freezing is a way to extend the shelf-life of food products using low temperature.
Under freezing temperature, some germs may be killed but some can survive.
However, no germ can grow at such low temperature.
(B) Deep-freeze cabinets used for long-term food storage should be maintained at a
temperature of -18℃ or below.
(C)Frozen meat and fish may be stored for up to six months and frozen fruits and
vegetables for up to one year.
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(D)When frozen food is thawed, the bacteria which have survived start to grow and
multiply again. Food, therefore, should not be thawed and refrozen. However, if
foods are partially thawed, for example, while shopping or as a result of power cut,
it may be safe to refreeze the food if the food is still frozen and the food is cold.
Once food is completely thawed, it should be used straight away. It is normally safe
to cook, thawed food and refreeze it as a cooked dish.
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8.5 Safe practices in defrosting (thawing)
Freezing prevents bacteria from growing, but does not kill them. Before cooking or
eating frozen foods, defrosting is required. Defrosting is a way to soften frozen food
into its original form. Improper defrosting (e.g. defrosting at room temperature) provides
an opportunity for food poisoning bacteria to grow and / or produce toxins. Therefore,
during defrosting, a good practice needs to be applied. Otherwise, the bacteria in food
may grow rapidly.
Four commonly used defrosting methods are:
❖ defrosting in refrigerator
❖ defrosting under running water
❖ defrosting by microwave oven
8.5.1 Defrosting in refrigerator
(A) A long defrosting time, usually overnight.
(B) Food should be wrapped to prevent contamination.
(C)We should place ready-to-eat (RTE) food and non-ready-to-eat food at upper and
lower shelf of refrigerator respectively.
(D)The defrosted food should be placed in refrigerator at all time until it is used or
consumed.
(E) Food should be used or consumed within 2 days.
8.5.2 Defrosting under running water
(A) RTE food should be wrapped before putting in water to prevent contamination.
(B) Non-RTE food could be defrosted without wrapping.
(C)Water should be kept running to facilitate faster defrosting.
(D)If the defrosted food is not used immediately, they should be wrapped and put in
refrigerator.
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8.5.3 Defrosting by microwave oven
(A) Food should be wrapped before putting in microwave oven.
(B) The defrosting should be divided into two phases. Food should be taken out for
stirring or turning over to facilitate adequate and even defrosting.
(C)Turn off the machine and wait for a few seconds before taking food out.
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Not for Sale
The copyright of the materials in this booklet belongs to the Education Bureau. The
materials can be used by schools only for educational purpose. Written prior permission
of the Education Bureau must be sought for other commercial uses.
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Family and LifeStyle