Transcript Food Hygiene

Food Hygiene
Food Hygiene
1.Relation Between Handling/ Manufacturing
Practices and Food Contamination
Food hygiene involves all measures necessary to ensure the safety and
wholesomeness of food durin
 preparation
 processing
 manufacturing
 packaging
 Storage
 distribution
 handling
 offering for sale or supply to the consumer
Food Hygiene
1.Relation Between Handling/ Manufacturing
Practices and Food Contamination
• This will involve:
 Rejecting contaminated food or food from unreliable sources;
 Decontaminating food;
 Protecting food from risk of contamination;
 Preventing any organisms multiplying;
 Destroying any harmful bacteria in the food.
 Discarding unfit or contaminated food
Food Hygiene
2. Biological, Chemical and Physical Hazards
2.1. Physical Hazards
• Are the most common type of hazard that occur in foods, for example:
 metal,
 glass,
 plastics,
 knife blades,
 hairs,
 pieces of wood, etc;
• The risk of consumer injury is quite low for most types of foreign material, as
few items are sharp or hard enough to cause physical damage are of
dimensions that might cause choking.
Food Hygiene
2.1.1. Sources, Vehicles and General Control Measures
• Foreign bodies found in food can be brought into food premises with the raw
materials or introduced during storage, preparation, service or display.
• Extrinsic foreign bodies may be considered as those that originate from:
 The Building, Installations or Equipment:
-Wood splinters;
-Flaking paint or rust;
-Glass.
Food Hygiene
2.1.1. Sources, Vehicles and General Control Measures
 Food Handlers
 The activities of maintenance operatives
 Pests or unsatisfactory pest control
 Packaging
 Cleaning activities
Food Hygiene
2.2. Chemical Hazards
Chemical hazards may occur in food and in the food service environment.
2.2.1. Sources, Vehicles and General Control Measures
The current main chemical hazard issues in food
products are as follows:
 Cleaning chemicals
 Pesticides
 Toxic metals
 Veterinary residues
 Chemical additive
 Allergens
Food Hygiene
2.3. Biological Hazards
• Biological hazards can be either macrobiological or microbiological.
• Macrobiological issues, such as the presence of flies or insects, while
unpleasant if found, rarely pose a risk themselves to product safety in
its true sense.
• Microbiological hazards are primarily bacterial pathogens but viruses
and parasites should also be considered.
Food Hygiene
2.3. Biological Hazards
Bacteria
 Viruses
 Parasites
Food Hygiene
2.3.1. Sources, Vehicles and General Control Measures
• Food poisoning bacteria may be brought into food premises by the following
sources:
 food handlers/ visitors;
 raw foods including poultry, meat, eggs, milk, fish and shellfish and
water especially when polluted with sewage or animal faeces;
 dust;
 pests.
• Cross-contamination can be defined as the transfer of bacteria from
contaminated foods to other foods.
Food Hygiene
2.3.1. Sources, Vehicles and General Control Measures
• Knowledge of sources, vehicles and routes is vital to food poisoning
prevention, as different controls apply to each.
• Prevention of contamination depends on either removing the sources,
or putting barriers between them and the vehicles or between them and
food.
• Routes must be disrupted by cleaning and disinfection.
Food Hygiene
3. Factors Affecting the Microbiological Growth
• The microbial growth can be simply illustrated by considering the case
of a bacterial cell dividing by fission to produce two daughter cells.
• A single cell will divide to produce two cells; after a further doubling
time has elapsed four cells will be present; after another, eight, and so
on.
Food Hygiene
3. Factors Affecting the Microbiological Growth
Fig. 1 - The microbial growth curve (Moss and Adams, 1989) .
Food Hygiene
3. Factors Affecting the Microbiological Growth
• A simple analysis of this curve can distinguish three major phases:
– the lag-phase, there is no apparent growth while the cells adjusts to the
new environment;
– the exponential or logarithmic phase which follows is characterized by an
increase in cell numbers following the simple growth law equation.
– changes in the medium as a result of exponential growth bring this phase
to an end as key nutrients become depleted, or inhibitory metabolites
accumulate, and the culture moves into the stationary phase.
Food Hygiene
3. Factors Affecting the Microbiological Growth
• The factors that affect microbial growth in foods, and consequently the
associations that develop, also determine the nature of spoilage and any health
risks posed.
• For convenience they can be divided into four groups:
Intrinsic Factors
Extrinsic Factors
Implicit Factors
Processing Factors.
Food Hygiene
3. Factors Affecting the Microbiological Growth
3.1 Environment factors
• Although it is often convenient to examine the factors affecting microbial
growth individually, some interact strongly.
Relative Humidity
• Relative humidity and water activity, aw, are interrelated, thus relative humidity
is essentially a measure of the water activity of the gas phase.
Temperature
• Microbial growth can occur over a temperature range from about – 8ºC up to
100ºC at atmospheric pressure. Bacteria are normally limited to a temperature
span of around 35ºC.
Food Hygiene
3.1. Environment Factors
Fig. 2 - Effect of temperature on growth rate (Moss and Adams, 1989)
Food Hygiene
3.1. Environment Factors
• Figure 2 showing the variation of growth rate with temperature illustrates
several important features of this relationship.
• Firstly, each organism exhibits a minimum, optimum and maximum
temperature (cardinal temperatures) at which growth can occur.
• These are known as cardinal temperatures and are, to a large extent,
characteristic of an organism, although they are influenced by other
environmental factors such as nutrient availability, pH and aw.
Food Hygiene
3.1. Environment Factors
Table I – Rang of temperatures for microbial growth
Temperature
(ºC)
Group
Minimum
Optimum
Maximum
Thermophiles
40-45
55-75
60-90
Mesophiles
5-15
30-40
40-47
Obligate Psychrophiles
-5-+5
12-15
15-20
Facultative Psychrophiles
-5-+5
25-30
30-35
Food Hygiene
3.1. Environment Factors
• In food microbiology mesophilic and psychrophiles organisms are generally of
greatest importance.
• Mesophiles
– with temperature optima around 37ºC;
– are frequently of human or animal origin;
– include many of the more common foodborne pathogens such as
Salmonella, Staphylococcus aureus and Clostridium perfringens.
Food Hygiene
3.1. Environment Factors
Psychrophiles
• Will grow down to that same low temperatures. There are two groups:
- Obligate Psychrophiles
- Facultative Psychrophiles
Thermophiles
• Are generally of far less importance in food microbiology, although thermophilic
spore formers such as certain Bacillus and Clostridium species do pose problems in a
restricted number of situations.
Food Hygiene
3.1. Environment Factors
Atmosphere Composition
• Its presence and its influence on redox potential are important determinants of
the microbial associations that develop and their rate of growth.
•The mechanism of carbon dioxide (CO2) inhibition is a combination of several
processes.
•The inhibitory effect of CO2 on microbial growth is applied in modifiedatmosphere packaging of food.
•CO2 is not uniform in its effect at microorganisms.
Food Hygiene
3.2. Food Composition
• The ability of microorganisms to grow in food is determined by the food
environment as wells as the environment in which the food is stored.
• These factors include:
nutrients;
growth factors and antimicrobials;
water activity (aw);
pH;
oxidation-reduction potential (Eh).
Food Hygiene
4. Microbiological Growth and their Implication in
Consumers Health
• A number of assessment of the relative significance of hazards associated with
food have concluded that microorganisms are of paramount importance.
• Similarly, it has been estimated that the risk of becoming ill as a result of
microbial contamination of the food was 100 000 times greater than the risk
from pesticide contamination.
• The foods that are most frequently incriminated in foodborne diseases in
Europe and North America are those of animal origin: meat, poultry, milk, eggs,
and products derived from them.
Food Hygiene
4.1. The Most Important Food Poisoning Bacteria
Salmonella
Clostridium perfringens
Staphylococcus aureus
Bacillus cereus
Clostridium botulinum
Vibrio parahaemolyticus
Escherichia coli
Listeria monocytogenes
Food Hygiene
4.2. Preventive Measures
• Prevention of contamination depends on either removing the sources, or
putting barriers between them and food.
• To prevent food contamination is essential to implement some good practices
and use appropriate technologies, such as:
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–
–
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Suppliers;
Reception;
Chilled storage;
Frozen storage;
Cooking;
- Thawing;
- Chilling;
- Modification of atmosphere;
- Hot holding;
- Reheating.
Food Hygiene
4.2. Preventive Measures
Suppliers
• The raw materials used in food manufacture should not be purchased from any
but approved suppliers, and it is hoped that suppliers to food manufactures will
operate effective strategies for the provision of adequate levels of customers
service and support.
• The initial selection of a supplier may be based on an evaluation of the supplier
against a number of criteria:
– national and/or international reputation;
–ability to provide products to agreed specifications;
– willingness to submit to supplier assurance audits;
–registration to ISO 9001:2000).
• The technical and quality requirements of raw materials used for the
manufacture of foods should always be clearly defined and the materials
should only be purchased product specifications.
Food Hygiene
4.2. Preventive Measures
Reception
 Unsatisfactory deliveries may introduce problems such as insects, rodents or
mould into the production area.
 To ensure that delivers meet the agreed specification, effective, documented
checking systems are advisable, systems required will depend on the type of
product.
 Checks may include: quantity, temperature, date code and quality, etc.
Food Hygiene
4.2. Preventive Measures
Chilled storage
• Chilled foods are those foods stored at temperatures near, but above their
freezing point, typically 0-5ºC.
• Perishable foods such as meat and dairy products and cooked foods that are
not for immediate consumption should be stored between 1ºC and 4ºC.
• These temperature limits are important from prevent microbial growth.
Food Hygiene
4.2. Preventive Measures
• If the chilling is consistently in breach of the critical limits, this may be the
result of over stacking.
• The air in the chilling unit should circulate freely around the produce so care
should be taken when storing food to prevent the development of warm spots.
• Since chilling is not a bacteriocidal process, the use of good microbiological
quality raw materials and hygienic handling are key requirements for the
production of safe chill foods.
Food Hygiene
4.2. Preventive Measures
Frozen storage
• Perishable foods may also be maintained at temperatures of -12ºC.
• Freezing and frozen food storage may be considered to be a critical control
point as freezing also prevents growth, multiplication and toxin production by
bacterial contaminants.
• Freezing in the most successful technique for long term preservation of food,
without that it has physical, chemical, biological or nutritional alteration of the
product.
• Foods begin to freeze somewhere in the range 0.5 to -3ºC.
• The temperatures used in frozen storage are generally  -18ºC.
Food Hygiene
4.2. Preventive Measures
Cooking
• Is a reliable method of ensuring the safety of food.
• The scientific literature would suggest that cooking to a core temperature of; at
least 70ºC for at least 2 minutes or achieving at least 75ºC are sufficient to
destroy bacteria.
• Lower cooking temperatures are permissible for gourmet dishes.
• However, the time-temperature combinations used should be validated to
ensure the destruction of bacterial pathogens and these dishes should be
consumed within 30 minutes of cooking, unless maintained at 63ºC or higher.
Food Hygiene
4.2. Preventive Measures
Thawing
• Thawing of frozen foods is a slower process than freezing.
• Even with moderate size material the outside of the product will be at the
thawing temperature some time before the interior.
• Slow thawing at lower temperature is generally preferred.
• Frozen foods should be thawed in the chilling device or if necessary using the
defrost cycle in a microwave oven.
• Thawing should never be performed at room temperature as any bacterial
pathogens on the surface of the food will have an opportunity to grow, multiply
and may produce toxins.
Food Hygiene
4.2. Preventive Measures
Chilling
 Cooked foods should be chilled immediately.
 If the latter is unavailable, the product should be placed in chilled storage
within 90 minutes of the completion of cooking.
Food Hygiene
4.2. Preventive Measures
Modification of atmosphere
• Modified atmospheres exert their effect principally through the inhibition of
fast-growing aerobes that would otherwise quickly spoil perishable products.
Obligate and facultative anaerobes are less affected.
• In practice three different procedures are used to modify the atmosphere
surrounding a product:
– vacuum packing;
– modified-atmosphere packing;
– controlled atmospheres.
Food Hygiene
4.2. Preventive Measures
• An essential feature of all three techniques is that the product is packed in a
material which helps exclude atmospheric oxygen and retain moisture.
• In Vacuum packing the product is placed in a bag from which the air is
evacuated, causing the bag to collapse around the product before it is sealed.
• Residual oxygen in the pack is absorbed through chemical reactions with
components in the product and any residual respiratory activity in the product and
its microflora.
• To achieve the best results, it is important that the material to be packed has a
shape that allows the packaging film to collapse on to the product surface entirely.
Food Hygiene
4.2. Preventive Measures
•In Modified atmosphere packing, a bulk or retail is flushed through with a gas
mixture usually containing some combination of carbon dioxide, oxygen and
nitrogen.
•The composition of the gas atmosphere changes during storage as a result of
product and microbial respiration, dissolution of CO2 into the aqueous phase, and
the different rates of gas exchange across the packing membrane.
• In Controlled-atmosphere storage, the product environment is maintained
constant throughout storage. It is used mainly for bulk storage and transport of
foods particularly fruits and vegetables.
•This has the effect of retarding mould spoilage of the product through a
combination of the inhibitory effect of CO2 on moulds and its ability to act as an
antagonist to ethylene, delaying fruit senescence and thus maintaining its own
ability to resist fungal infection.
Food Hygiene
4.2. Preventive Measures
Hot holding
 Is a temporary measure and should be applied for as short a period as possible.
 Food should be placed in the bain-marie or other hot holding device before the
temperature decreases to below 63ºC and held at will facilitate the growth and
toxin production by bacteria.
Reheating
 Pre-cooked foods that are not served at chilled temperatures should be heated
immediately after removal from chilled storage to a core temperature of not
less than 70ºC, should not be reheated more than once and should be served
within 30 minutes.
 While reheating will destroy most bacterial cells, pre-formed toxins may remain.