FOOD SPOILAGE
Food spoilage starts immediately food is harvested, gathered or slaughtered it begins to
deteriorate until eventually it becomes unsafe for consumption. This deterioration is termed food
decay and leads to food spoilage.
Food spoilage is cause by two main factors:
1. Natural decay within the food itself.
2. Contamination by microscopic forms of life (micro – organisms).
Foods which spoil rapidly are called perishable foods and usually contain relatively large
amounts of water and nutrients. Examples are milk, and meat. Processed and cooked foods
Food borne illness and alllergies
Food poisoning
Food poisoning is a general term for foodborne illness.
Food poisoning develops as a result of a pathogen’s infecting someone is called a food borne
infection
When food poisoning caused by toxins produced by the pathogen, it is called food intoxication,
and in the case of botulinum, it can kill.
Toxins can be produced by bacteria during food preparation or storage or by bacteria in one’s
digestive tract.
PREVENTION OF FOODBORNE ILLNESS
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Most foodborne illnesses do occur because of the ignorance’s or carelessness of people
who handle food. People can introduce pathogens to food, preventing them from reaching
it, or kill them with appropriate cooking temperatures.
Cleanliness is especially important in preventing foodborne illness.
For example, when kitchen equipment such as a cutting board, meat grinder, counter top
is used for preparing pathogen infected foods and not cleaned [properly afterward,
noninfected food that is subsequently prepared with this equipment can become infected
by the same pathogen(s). this is called cross-contamination.
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Dishes used to hold uncooked meat, poultry, fish or eggs must always be washed before
cooked foods are placed in them.
When food workers fail to wash hands after blowing their noses or using the toilet, they
can “share“ their germs very easily.
Mucus and feces are favourite breeding areas of pathogens
Food handlers who have small cuts on their hands must wear gloves because a wound
could carry a pathogen.
Foods must be covered and stored properly to keep dust, insects, and animals from
reaching and possibly contaminate them
ooked foods e.g .frozen, canned, dried are also easily susceptible, once thawed, opened or
reconstituted. Food s which contains relatively low amounts of water or high concentration of
salt, acid, or sugar, is less readily affected.
NATURAL DECAY
Natural decay in food is the result of
Moisture loss and the action of enzymes. This is usually found in vegetables, meat, fish, and
cheese due to evaporation from the surface.
Action of enzymes - Many enzymes are present in foods, and some remain inactive until a food
is harvested or slaughtered .Once activated, such enzymes speed up the process of decay by
breaking down the tissues and components of the food in deferent ways, including
1. Oxidation – Vitamin C, thiamin, and carotene are affected by oxidation
2 .Browning e.g. cut apple
3. Ripening – fruits and vegetables e.g. unripe bananas
CONTAMINATION BY MICRO-ORGANISMS
The main micro – organisms responsible for the contamination of food are bacteria, moulds and
yeast
Micro – organisms contaminate food by producing waste products or toxic (poison) or simply
make the food inedible by their presence and in some cases cause illness or food poisoning.
Some micro – organisms are used in the industry for the production of cheese, yogurt and soy
sauce .Harmful micro - organisms are called pathogenic (harmful) micro-organisms.
BACTERIA
Bacteria can be found in many places ,including :air ,water ,soil ,sewage, food ,plants ,animals
(including man) ,dust etc . These can be classified according to their shape:
Spherical bacteria – these are called Cocci -..Streptococci these cause diseases such as scarlet
fever and tonsillitis they also form pairs called diplococcic which are the cause of pneumonia
Staphylococci are the cause of boils, septic wounds and food poisoning.
Rod –shaped bacteria called Clostridium – causes diseases such as diphtheria, tuberculosis,
typhoid and food poisoning. Some have spiral shaped and are responsible for the cause of
cholera, syphilis and infectious jaundice.
REPRODUCTION OF BACTERIA - Under suitable conditions of temperature moisture and
food supply bacteria can reproduce very rapidly, they produce by dividing into two, under the
right condition a
CAUSES OF FOODBORNE ILLNESS
TABLE
NB. Single bacteria cell can give rise to 16,000,000.
Bacteria type
Name
Illness
Symptoms
Causes
Notes
Severe
vomiting,
diarrhoea,
exhaustion.
Nose, skin,
cuts, sores;
cooked
meat, pies,
Custards, ice
cream.
Faeces,
sliced
cooked
meat,
poultry,
pies,
sausages,
eggs
Double
vision,
difficulty
1. Poisoning
due to
toxins.
2. Heat does
not
destroy
toxins
Main cause of
food poisoning in
UK.
fatal
Incubation
Duration
Coci
Staphylococcus 1-6 hrs
6hrs
1-
Bacilli
Salmonella
Typhimurium
12 48 hrs 7days
Headache,
fever,
vomiting,
abdominal
pain
Clostridia
Clostridium
12 to 36 hrs
Fatal within
fatal
.
with
breathing,
talking,
swallowing
Bacilli
Clostridia
Bacillus cereus
clostridium
Welchii
Bacilli
Salmonella typhi
bacilli
Bacillus cereus
2-18
8-24hrs
1-3weeks
2-18
1-3days
Vomiting
Diarrhoea
Abdominal
pain
1-2days
1-2months
1-3days
Faeces, cold,
meat, gravy,
cream,
sausages
Poisoning caused
by bacteria in
body
diarrhoea
abdominal pain
headache
headache,
Tiredness
Fever ,rash
Haemorrhage
meat, pies,
poisoning due
gravy, canned
to toxin and
meat, soil
bacteria in gut
sewage, water
can be
flies, cream
fatal, slow
cake
recovery
watercress
Canned meat
vomiting
faeces, cold,
poisoning
diarrhoea
meat, gravy
caused by
abdominal pain
cream,
bacteria in
sausages
body
The effect of heat on bacteria
Some bacteria can withstand extremes of temperature, but are destroyed at temperatures of around 60 o C
(140 F). Bacteria are able to multiply most rapidly at around 37 C (933.4 F ) , AND THIS HAS
IMPORTANT IMPLECATION S FOR THE PRESERVATION OF FOOD BY heat .
Other effects - many bacteria are affected by high concentration of salt, sugar, or acid .
Contamination of food by bacteria
Food Poisoning
Bacteria can be transferred to food by several means, including:
1. Using the same utensils to serve contaminated food and other foods.
2. Careless attention to personal hygiene while handling food e.g. not washing hands after
visiting the toilet, touching nose while preparing food.
3. Leaving skin infection and cuts uncovered while preparing food.
4. Coughing, sneezing, or spitting while preparing food.
5. Incomplete cleansing of food utensils and serving dishes.
6. Pests e.g. houseflies, cockroaches, beetles, certain moths.
7. Rodents e.g. rats, mice.
8. Household pests, e.g. dogs, cats, hamsters.
9. Infected or diseased cattle and dairy cows.
10. Contaminated water supply.
11. Soil and dust.
Once bacteria have been transferred to a food, they will grow and multiply under the
Following conditions;
1.
2.
3.
4.
Incomplete thawing and cooking of certain foods e.g. poultry, pork.
Holding cooked foods e.g. chicken, shellfish, at room temperature before serving.
Incomplete or repeated cooking of leftover food.
Careless storage of food.
Reasons for the increase in the number of cases of Food poisoning
1. Eating a greater number of prepared foods e.g. Meat pies, pastries, partly cooked breads
2. Eating at restaurants, take- always shops, and hotels
3. Import of foods from countries where food hygiene laws may not be strictly enforced
4. Insufficient training of staff who handle food
MOULDS
Moulds are tiny plants, which are visible to the naked eye. They grow on many types of food,
especially cheese, bread, kenkey, T.Z., and fruit.
CONDITIONS SUITABLE FOR THEIR GROWTH
They require warm moist conditions to grow, but are able to grow at a slower rate in cool places.
Mould growth is prevented by:
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cool dry storage
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heating to destroy moulds and spores
acidic conditions
Moulds reproduce by means of sporulation .Sores are released into the atmosphere and carried in
the air .If they land on a suitable food, the spores germinate, and a new mould appears. This
process is called sporulation.
Note: foods that are often contaminated by mould appear to be safe to eat as only the outer part is
affected by mould growth. However , resent research shows that substances produced by mould
growth can migrate into food could be harmful to many organs of the body .These substances are
called mycotoxins .It is therefore, adviceable to discard mouldy food completely ,rather than just
to remove the mouldy part.
YEAST
Yeast are found in the air and soil and on the surface of fruits .Some are able to tolerate fairly
high acidic ,salt and sugar concentrations and can grow without the presence of oxygen.
Yeast reproduces by budding and would need the following conditions to grow, water, warmth
and food.
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Yeast cell remain dormant in very cold conditions, and are killed at temperatures
approaching 100 C.
Growth is inhibited in the concentration of high salt
Yeast can spoil foods such as jam and fruits by fermenting the sugars to produce alcohol
and carbon dioxide gas
Food can be contaminated from other sources such as Chemicals, Radiation, and Pollution.
Hygienic practices in the handling and preparation of food
The hygienic handling and preparation of food are of great importance in the prevention of food
contamination and food poisoning .This can be achieved by following rules:
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Personal hygiene
Kitchen hygiene
Food hygiene