Download T_10_EN_Food hygiene

Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
TOPIC 10
FOOD HYGIENE
Definition of food hygiene
Food hygiene is a concept and even a set of activities that are applied to reduce the risk of
food borne illness and food adulteration.
To manage food hygiene in order to keep consumers` health it is important to know who
are the enemies and haw to fight against them. But the major desire of food hygiene is to prevent
the danger in order to keep health and wellbeing.
Food hygiene is managed in the frame of food safety, its activities being oriented to
prevent any danger for the human health that can be related to food consumption.
Possible food safety dangers (hazards)
Food can be related with a large variety of dangers named also hazards that can disturb
food safety and cause directly or indirectly food related or food borne illness.
The possible food safety dangers related to food consumption can be classified in:


Physical dangers like pieces of metal, wood, plastic, glass, bandages, etc.
Chemical dangers like toxins (Exp. from the food composition, from processing,
etc.), pesticides (for different use, different chemical formula), heavy metals (Exp.
mercury, lead, etc.), persistent organic pollutants (POPs), food additives (Exp.
preservatives, nutrient supplements, color and flavor enhancers, antibiotics,
growing hormones), allergens, and other substances like sanitizers or lubricants. In
this category are included also microbial toxins (botulinum, mycotoxins (Exp.
aflatoxins, patulin, vomitoxin, fumonisins), microcystins (blue-green algae toxins).
 Biological dangers like viruses (Exp. Rotavirus, Hepatitis A, Cytomegalovirus, HIV),
bacteria (Exp. Listeria monocytogenes, Escherichia coli, Salmonella, Shigella,
Enterobacter, Staphylococcus), protozoa (Exp. Toxoplasma gondii, Giardia lamblia,
Entamoeba histolytica), parasites (Exp. Echinococcus, Anisakis simplex, Ascaris
lumbricoides Trichinella species), prions, pests (Exp. Rodents, Flies, Cockroaches).
The sources of food contamination are animals, peoples and the environment.
Source of pathogenic or harmful microorganisms (bacteria, viruses) are for example the animal or
human intestinal tract for Salmonella, Esherichia coli, humans for Shigella, Hepatitis A virus,
Norovirus, Staphylococcus, the environment for Listeria and Clostridium and water for most of
them.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
1
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
Damages produced on food by different food safety dangers
The food hazards can produce different transformation related to food presentation or
composition. They can act during production, storage, preparation and consumption of each food
product.
The most usually dangers related to food are food poisoning and food adulteration.
Food poisoning is given by the content of different kinds of toxins. Toxins are chemical
substances that are dangerous for the human body. In the case of toxins contained by food, they
act after ingestion at different levels of the digestive system where they cause illness.
Toxins come from the food composition like poisonous mushrooms or from bad handling,
processing or packaging like pesticides, sanitizers, lubricants. During storage and preservation can
results toxins from chemical reactions during adulteration like amines, amides, H 2S or toxins
resulted after the metabolic activity of spoilage microorganisms like botulinum.
Food adulteration is a modification of the food quality. It can be cased by bad handling
that lead to contamination with harmful microorganisms and parasites during production,
processing, preparation and manipulation, bad storage and preservation by the environment that
stimulates the development of harmful microbial activity and harmful chemical reactions in the
food composition. Also bad packaging that had leaks where harmful microorganisms and
dangerous substances can enter and damage the food can cause food adulteration.
Parasites usually don’t consume food but they damage food by their presence because
food became their carrier to the human body.
Adulteration can be produced also by pests (Exp. Rodents, Flies, Cockroaches) that
consume food and damaged it with urine, hair and different pathogen microbes and parasites they
carry.
Food adulteration can be classified in:


chemical adulteration produced by chemical reactions induced by food enzymes
microbial adulteration produced by the metabolic activity of spoilage
microorganisms
 pest and parasite adulteration by the presence and activity of different parasites
and pests.
The most important adulteration (spoilage) microorganisms are spoilage bacteria, moulds
and yeasts.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
2
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
The relation between food safety dangers and food
Food products are entities that are produced and handled in the surrounding environment.
The environment is represented by soil where the vegetable food as raw material growth, by the
air, water or different objects with which the food product comes in contact during its handling
like different surfaces, plants, animals or humans. The animal raw food products are also
surrounded by air and come in contact with different kinds of objects and surfaces during
handling, preparation and storage.
Microbes doesn’t find good condition to growth in the air but they can survive here for a
long time, being handled on different surfaces, even on food or different objects related to food
(tables, dishes, glasses, eating utensils) or on the human body, most our hands. They get in air
from the soil, different plants and animals, or humans.
The whole environment and every object or being contain different kinds of microbes,
toxins and/or parasites or pests that pass from their own surface on the surface of the food by
contact. Their migration is influenced by gravitation, air currents and also by direct contact. The
passage of microorganisms or toxins from the environment to the surface of food is named
contamination. From the food surface, the microbes can migrate in time into the depth of it.
The contaminating microbes can be indifferent but also spoilaging for the food or
dangerous for the human health.
Food can be a vehicle and a nutritional support for microorganisms.
As vehicle food is not disturbed by microbes living on its surface. In this case the food
product can transport microbes from a place to another and also to the human body if this food is
eaten. It’s the case of not harmful microorganisms that live on the food but doesn’t produce any
disease if they are ingested and also they don’t induce transformations in the food composition or
presentation. Here we can mention all autotrophic bacteria that consume only inorganic mater.
If food is used to provide space and nutrients for microorganisms and pests, these are not
only present on/in the food product but determine also different kinds of transformations on its
appearance and composition. During this transformation dangerous substances can be generated
like amides, amines, H2S, substances related to spoilage and representing food adulteration. Also
toxins can be developed during microbes` metabolic activity that poisons the food product. To
these categories belong a large variety of organotrophic microorganisms like putrefaction bacteria.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
3
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
Food as a vehicle for diseases
Microbes are in a large variety in every environment. Some of them are not harmful, but
most of them are harmful for human health.
Harmful microorganims can be transferred by to food by people, equipment, utensils,
other foods or pests.
They can be directly harmful if it is the case of infectious microorganisms like viruses,
pathogen bacteria (Exp. Listeria monocytogenes, Escherichia coli, Salmonella, Shigella,
Enterobacter, Staphylococcus), prions or parasites (Exp. Echinococcus, Anisakis simplex, Ascaris
lumbricoides, Trichinella species).
Some of them contaminate food and don’t produce any transformation on its composition,
because they don’t find here conditions to develop. They became dangerous if they are ingested
with the contaminated food and reach different levels of the gout. Here they find good conditions
and became metabolic active producing illness. Illness is produced by different kind of toxins
secreted by these microbes in the gout (Exp Salmonella, Staphylococcus, Ascaris lumbricoides,).
The level of produced toxins depends on the number of ingested dangerous microbes. Their
number increases in the gout by multiplication in the good environmental conditions found here
and the level of toxins increases too. These toxins induce illness.
In other cases microbes or parasites migrates after ingestion from different levels of the
digestive system to other organs of the human body where they multiply using as nutritional
support different compounds from the human cells (Exp. some viruses, Staphylococcus,
Echinococcus, Trichinella species). Their activity causes illness, even if it is not related with toxin
elaboration.
These kinds of microbes and parasites induce food spread diseases.
Some other microbes and parasites are indirectly harmful. It’s the case of spoilage
microorganisms like some kinds of bacteria (Exp proteolytic and lipolytic bacteria), yeasts and
moulds that induce food adulteration. During spoilage they induce the production of some toxic
substances by the transformation of different food compounds they consume as nutrient. For
example proteolytic spoilage bacteria determine the advanced hydrolyses of proteins from the
food composition and produce poisonous amines, amides and H2S. Lipolytic bacteria produce
oxidation of fats with the release of free radicals that are harmful for human health. These
microorganisms and parasites generate diseases related to food adulteration.
Foodborne illnesses may be passed on by pests like rodents, flies and cockroaches and
their droppings and urine.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
4
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
The above mentioned two microorganism categories, parasites and pests induce food
borne diseases.
All diseases generate different kinds of specific symptoms altering well being of the human
body.
The harmful microbes, parasites and pests reach food by contamination from air, water,
animals and plants, other food like raw food products, ready to eat vegetables and fruits, food
prepared/stored in not proper conditions, from different equipments and utensils, from people
and the whole environment.
To produce illness the microbes or parasites has to enter the human body by ingestion of
contaminated or adulterated food. If the food is contaminated with infectious microorganisms or
parasites the term infection is used.
Symptoms to recognize a food borne illness
Illness is recognized in general by a general bad status of the whole organism. Different
kinds of diseases are recognized by some specific symptoms.
The most usually symptoms related to a food borne illness are nausea, vomiting, diarrhea,
weakness, headache, abdominal cramps, fever and chills.
The symptoms are related to different stages of the microbial development into the human
body. So, at first, during ingestion of a damaged food, when the harmful microorganisms enter the
human gout, there are no visible symptoms. After these microbes find good developmental
conditions (nutrients and a good environment) they begin their metabolic activity that leads to
toxin production and increasing in their number. Now the first symptoms became visible as
weakness, headaches, nausea. In a further stage there appear vomiting, diarrhea, abdominal
cramps all these being accompanied by fever alternated by chills. It’s the highest time for the
doctor intervention.
Food related and food born diseases are dangerous to all kind of people. The highest risk
groups are children, pregnant women and elderly persons.
To prevent food born and food spread diseases it is necessary to keep good hygiene
practices.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
5
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
How can hygiene prevent food related diseases
Being related with the concept of managing food dangers that induce food spread and
food borne diseases, hygiene is oriented in two directions to prevent and to combat these
dangers. To realize this desideratum hygiene recommends a set of rules and activities to reduce
the risk, to recognize a potential danger before it is manifested and to take the best attitude and
make the best activities to remove a manifested danger and to restore the normal condition that
guarantees human health and well being.
Hygiene must keep an eye on observing the presence of physical, chemical and biological
dangers in the food and even every sign that can indicate its adulteration. In general the presence
of a danger is related with adulteration because most the biological dangers act on the food
product inducing its transformation.
The presence of any danger can be identified by analytical analyses of a potential danger.
This needs special equipments, personnel and laboratories to analyze the presence and amount of
microbes or toxins in the food. It’s the charge of food control institutions.
It can be done also easier by a simple observation of some changes in the specific
characteristics of any food product like surface appearance, color, texture, smell, presence of
some abnormalities, etc. that can be observed by anyone if paying attention and had to become a
general practice of each consumer.
The goals of food hygiene rules are:
o To prevent food contamination by practice good personal hygiene, clean and
sanitize and separate handling to prevent cross-contamination
o Prevent/Eliminate microbial growth by the four food safety principles (Clean,
Separate, Cook, Chill)
Hygiene practices to reduce the risk of food related illness
The pratices to reduce the risk of food related illness has to prevent the contamination and
spread of a physical, chemical or biological hazard. The most frecvente and dangerous hazards are
the biological ones so they has to be taken into account at first.
To use hygiene practices it is important to analyze why to do a specific action?; what to do
?; how to do it ? and when to do it ?
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
6
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
1. Hygiene practices to prevent contamination
Contamination is prevented by a good personal hygiene and by cleaning and sanitizing.
Good personal hygiene is sometihg well known nowadays but it had to be made conscious
to reach the expected result. This means that each person had to be clean, to have a clean body,
clean hands, a clean mouth and clean clothes.
A special attention is to be payed on cleaning hands becausse hands are the part of our
body that comes most in contact with different surfaces and objects, hands being also used to
provide food intake.
So washing hands had to become a general practice for each person most before eating,
after using the toilette, after coming home, before and after doing a job, etc. This activity has to
become a custom that will be learned by children at early age and arrive a lifetime habit for each
of us.
Hands had to be washed with warm water and soup if possible because in this way a larger
amount of microorganisms are removed.
The body had to be kept clean by taking a bath whenever it is necesary because our hands
came in contact with other parts of our body and can take microbes from here.
A clean mouth is a precondition of our health because in the mouth there are many
microorganisms that can migrate with the ingested food into the gout. Sometimes here are
present even harmful microbes most if our teeth are dameged. A regular teeth brushing with
toothpaste is a precondition to prevent food spread deseases because in this way a large number
of microbes are removed from the mouth.
Clothes cover our body and come also in close contact with our hands and sometimes even
with the food during eating and can provide microbial contamination.
As we saw personal hygiene includes a set of rules that had to be followed by everyone
from early childhood. These rules had to become good habits to prevent food related deseases.
Cleaning and sanitizing are actions that will be applied on each surface and object that
come in contact with food and even on the food itself in order to remove harmful microorganisms
and parasites. Pests had also to be eliminated from spaces related to food preparation and serving
because they carry many pathogenous microbes.
Cleaning is a physical removal of soil and dirt made with water in order to remove
microbes and other potential dangers related to food. If possible it is recomanded to use runing
water that removes best the microbes. Fresh and raw food had to be compulsory washed with
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
7
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
running water. It is recommended to wash different surfaces and objects with warm water,
because in this way some microbes are killed by its temperature.
Cleaning is an action made on food and objects (utensils, equipments) and surfaces that
come in contact with food during its processing, preparation, storage and consumption.
Cleaning is made by wetting, applying soap, scrub, rinse and dry. Cleaning is made each
time before the object or surface come in contact with the food.
If the objects or surfaces are expected to be dirty or to have a large amount of microbes it
is necessary to apply also sanitization.
Sanitization supposes the supplementary washing with different solutions of chemical
substances named sanitizers like chlorine, quats, iodine, etc. that have a toxic action on the
microbes and kill a larger amount of them preventing in this way better a food contamination and
even eliminate microbial growth, parasites and pests until a safe level. Sometimes hot solutions
are used to potency the destructive action upon the microbes.
Sanitizers are toxic substances even for the human body so they have not to be ingested. It
is compulsory to use them in the lowest concentration that provides their lethal action on
microbes and also to remove them after application by cleaning with water.
Sanitization is applied on utensils, equipments, surfaces related to food handling each time
we suppose the presence of a large amount of microbes or the presence of harmful microbes,
parasites or pests.
There is a relation between cleaning and sanitization. If the risk of a microbial and parasite
contamination is expected to be low cleaning is enought. If the risk encrese and there are
infectious microbes, parasites and pests present it is necesary to apply olso sanitisation.
Because of its toxicity sanitisers are never directly aplied on food products, only on objects
and surfaces with which they come in contact.
2. Hygiene practices to prevent cross contamination
Cross contamination means the spread of microbes, parasites or pests from a food product
to another by direct or mediated contact.
To prevent cross contamination food products had to be handled separate.
Separate handeling means to put different types of food on separate places during
shopping, washing, storing and using.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
8
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
For exemple animal products like meat and milk products has to be handled separate
from vegetable and fruit products because each type of food product has its own microbial charge.
Animal deriving products (Exp. meat, milk, fish, egg, seafood) contain more adulteration
microbes that produce proteolyses and lipolyses. Here we expect to find also more infectious
microbes and parasites originated in the animal from where the food come. These microbes and
parasites can be caried to the human body and develop specific deseases on humans. During this
passage they can increase their number because animal tissues provide a good nutitional
environment for them.
Vegetal products carry more adulteration microbes that produce carbohidrates hydrolises.
They can be less contaminated with infectious microbes and parasites depending if they were
grown in soil and infected waste water was used to irigate them. Washing them in running water
is suficient to remove this hazards because they don`t use these products as nutritional suport.
For example, when vegetables are cut on the same cutting board as raw meat without the
cutting board being properly cleaned and sanitized before, cross contamination occurs.
So it is compulsory to use separate bags if shopping them, different plates to handle them
during preparing our meal, separate shelves to store them in the refrigerator.
3. Hygiene practices to prevent food adulteration
Food adulteration is a major cause of food borne illness because during adulteration
microbes develop dangerous substances in the food (their own toxins or toxic metabolites).
To prevent adulteration bad environmental conditions has to be created in the food
product or the microbes have to be destroyed.
The most used bad environment for the development of harmful microbes is using low
temperatures by chilling.
To kill the dangerous microbes and even parasites and pests hot temperature is used by
cooking.
So to prevent adulteration by microbial groth it is important to keep food cold, hot or to
don`t keep it.
Chilling is applyed to prevent or slow down the grouth of microbes by decreasing their
metabolic activity and prevent their multiplication.
Chilling is performed at a temperature of 0-4oC by refrigeration and at lower temperature
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
9
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
of -20 until -8oC by freezing.
During chilling it is important to keep each food product at the right temperature to
prevent its adulteration during storage and afterthen during preparation.
Refrigeration is applied if storage of food is necesary to keep the whole quality of the food
product (Exp. Milk, eggs, perisable fruits and vegetables, meat products, etc.) for not a very long
time. A large vaiety of food products need storage at refigeration. This is related to their low
conservability. Conservability is the capacity of food to mentain in time all sensory, nutritional,
chemical and microbial characteristics. Refrigeration try to extend their freshness.
Freezing supose lower temperatures that turn the watter from the food cells in ice. In this
way a longer preservation time (Exp. some weeks or month) is possible because all microbes and
food cell enzimes became inactive. Most of the microbes remain alive during freezing and became
active after thawing frozen food. Because of this it is neccesary to respect some rules during
thawing frozen food in order to prevent the activity of the microbes contained by the food. So, it is
neccesary that thawing happens as quickly as possible so that during thawing the microbes remain
inactive. This is realised most by using the frozen food drectly during food preparation without
thawing. In this way the microbes have no time and environment at proper conditions to become
methabolic active and induce adulteration.
In industrial condition a deep freezing at -40oC is used. In this conditions not only
inactivation of microbes is achieved but also their death so that thawing is not so dangerous.
Cooking is used to prepare special meals. By cooking we understand all kinds of high
temperature treatments of the food as boiling, grilling, baking, etc.
During cooking most harmful but also unharmful microorganisms are distroied by heating
at high temperature. The high temperature will kill most of the microbes from the food and
inactivates the microbial and foodborne enzimes so that the conservation of the food is extended
if the right cooking temperature is used.
The right temperature must be chosen according the food type (higher for more consistent
food) and the geometry of the cooked food pieces (the larger the pieces the higher the
temperature). Food is safely cooked when it reaches a high enough internal temperature to kill
the pathogenic bacteria that cause illness.
The success of inactivation of harmful microbes and enzymes is given by the relation of
temperature and cooking time. So we can use efficient a lower cooking temperature and cook for
a longer time, or it is enough to use a shorter cooking time if using higher cooking temperature.
Cooking is used at home, in restaurants and cafeteria to prepare meals. Most of them are
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
10
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
eaten immediately after coooking. The not consumed cooked food is stored most at refrigeration
temperature and eaten later after reheating.
Reheating is allowed to be used only if the coocked food is secure not to develop a
chemical or biological danger during storage at refrigeration and reheating. So, some cocked food
can be contaminated after cocking with spoilage microorganism from the environmental air or by
contact from the cooking vesels, because cooking is never made in steril condition. If the person
who cooked the meal is ill or handle the food not in hyghienic condition even infectious microbes
can be found in the cooked meal. During storage some these microbes survive, some of them that
like low temperature can develop and induce a potential adulteration. More, during reheating also
other microbes that like higher temperature can develop and produce adulteration.
In industrial conditions food is treated in order to prevent its adulteration with high
temperature treatment by pasteurisation or sterilisation.
Pasteurisation supose a treatment at high temperature (around 100oC) for a short time so
that only a part of the microbes a killed. The pasterurised food had to be stored at refrigeration
temperature not for a long time (Exp. pasterurised milk) .
Sterilization is a harder high temperature treatment (around 120 oC) that kills all kinds of
microbes from the food, alowing its further storage at room temperature for a long time (Exp.
canned meat or fish).
4. Hygiene practices during food handling to reduce risks
All above mentioned hygiene rules had to be kept during food handling in order to reduce
any risks for food safety.
For food safety reasons it is important to know if the surrounding air, the surfaces that
come in contact with food, different objects related to food handling and even the food itself
contains microbes, the amount of this microbes and their kind.
Analyzing the presence and amount of microbes in the air, from different surfaces, our
hands, different objects relate to food and different food products, a future danger for the food
adulteration and the health of the consume can be provided.
The pathways of food contamination in each environment are also important to be known
in order to establish the best hygiene practices to be applied at each point established as
dangerous.
The most important practices during food handling can be considered:
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
11
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
 Quickly handling in the dangerous temperature zone
 Sufficiently cooking or reheating to destroy harmful microorganisms
The dangerous temperature zone is the temperature range between which the most
harmful microbes, parasites and pests are metabolic active and can produce food adulteration or
can survive, reach into our body and produse infectious diseases.
This temperature danger zone is between 5oC and 60oC where microbes can multiply
quickly on potential contaminated food that is stored in this temperature range.
Keeping food above 60oC will prevent growth of microorganisms and destroy harmful
microorganisms. Above 63oC food poisoning microbes are killed. Above 100oC all microbes are
killd. In the range of 5-60oC micbrobes are methabolic active the most of them between 20-40oC.
Below 5oC began the microbial inactivation. This is realized in the refrigerator. Below 0oC in th
freezer all microbes are asleep.
Food has potential to cause illness if it is exposed to temperatures in the danger zone for
more than 4 hours or it is not cooked or reheated sufficiently to destroy harmful microorganisms.
Keeping foods below 5oC will prevent or slow down the growth of microorganisms and
parasites.
Pathogenic bacteria multiply also rapidly at temperatures in the range of the danger zone
Keeping foods cold is the most effective way to reduce the risk of foodborne illness. It is
also compoulsory to pass foods through the temperature danger zone quickly and as few times as
possible. Frozen food had to be thawn as quickly as possible in the refrigerator, submerged under
cool running water, in a microwave or as part of the cooking process.
Hygiene in home and industrial conditions
At home conditions most food products are consumed after preparation so they passes the
following flow: purchasing, receiving, storage, preparation, cooking, holding/serving,
cooling/storage, reheating.
In industrial conditions each food product passes a way from the place where it is produced
until the place where it is consumed. This passway is named food chain and contains the following
links: producer, distributor, consumer.
For food safety reasons it is important to analyze the food flow in order to identify the
dangers associated to each chain link to prevent spread and growth of dangerous microbes and
parasites during passing each link of the food chain. It is important to know what happens during
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
12
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
each link and what practices had to be apllied to manage food contamination and adulteration to
prevent food spread and food born illness.
The most common practice to prevent food adulteration and poisoning is food
preservation. It prevents food related illness by inactivation of food enzymes, food toxins and
microbial toxins, inactivation of microbial growth and death of microorganisms and parasits.
The modalities to prevent adulteration and poisoning are: to preserve food keeping it in
controlled environment, cooking it by boiling, grilling, baking, etc., conservation by lactic acid
fermentation, acidification with vinegar, high concentration of sugar or salt, storage at low
temperature by refrigeration or freezing, high temperature treatments by pasteurization,
sterilization, UHT treatment or applying other methods like radiation, ultrasound, etc.
It is also important to identify the critical point where adulteration can occurs in order to
apply the preservation measures. Critical points are during production, storage, preparation and
consumption.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
13
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
PRACTICAL ACTIVITIES
MIGRATION OF MICROBES AND THEIR IMPACT ON FOOD POISONING
General objective of the work: To highlight the presence of microbes in the environment, the
ways they migrate until contaminating food and poison it, the environmental and human related
factors that interfere and haw can we manage them.
Objectives:
 Identification of the presence of microbes in the environmental air
 Identification of the presence of microbes on different surfaces and objects related to food
 Identification of the presence of microbes on our hands
 Identification of the presence of microbes on food
 Investigation of the migration pathways of microbes during food handling.
 Investigation of the environmental factors that can influence the handling of microbes.
 Investigation of human actions that can influence microbes’ migration and food
contamination.
Premises:
Food is present in the environment where it is surrounded by air and everywhere in the air there
are present different kinds of microbes. Microbes doesn`t find good condition to growth in the air
but they can survive here for a long time, being handeled on different surfaces, even on food,
different sufaces and objects related to food (tables, dishes, glases, eating utensils) or on the
human body, most our hands. They get in air from the soil, different plants and animals, or
humans.
Their migration is influenced by gravitation, air currents and also by direct contact.
The contaminating microbes can be indifferent but also spoilaging for the food or dangerous for
the human health.
For food safety reasons it is important to know if the surrounding air, the surfaces that come in
contact with food, our hands and even the food we eat contains microbes, the amount of these
microbes and their kind.
Analizing the presence and amount of microbes in the air, from different surfaces, our hand and
different food products we can provide a future danger for the food spoilage or the health of the
consumer. We can also establish the pathways of food contamination in each environment.
Problem questions:
Are there microbes present in air?
Are microbes present on different surfaces that come in contact with food?
Are microbes present on our hands?
Can our hands and different surfaces spread microbes on food?
Is food contaminated by microbes because it’s contact with air, different surfaces and objects?
Why are microbes present in air, on different surfaces, on food?
Are microbes present everywhere in the environment?
From where come microbes in air, on different surfaces, objects and food?
What do they do in the air environment?
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
14
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
Haw can microbes land on different surfaces, objects and food from air?
Haw can microbes be disseminated from one object to the other, even to food?
What factors influence microbe presence and migration?
Haw can they interfere with food and human health?
Haw can we identify them?
What information can we gather from their presence?
What can we do to restrict their presence?
Lets investigate:
o The presence of microbes in air
o The presence of microbes on different surfaces and objects related to food (tables, dishes,
glases, eating utensils)
o The presence of microbes on our hands
o The presence of microbes on different food products
o The migration pathways of microbes during food handling
o The environmental factors influencing their precence and migration
o The human actions that can influence microbes’ migration and food contamination.
Identification of the presence of microbes in the environment related to food
and the ways of food contamination
Experiment design (practical activity organization):
1. Divide the students from the classroom in four groups. Each of them will perform a kind of
practical activity as follows:
o Identification of the presence of microbes in the air from different environments
o Identification of the presence of microbes on different surfaces (tables, desks) and
objects related to food (dishes, glasses, eating utensils like forks, spoons)
o Identification of the presence of microbes on our hands
o Identification of the presence of microbes on food (packed /unpacked)
2. Establish for each activity 3-4 sampling points.
3. Prepare the sampling dishes (plates) previous starting sampling in each experimental
activity in the lab. Plates can be bought ready to be used.
4. Realize sampling as field activity. Sampling can be performed by the students at home, in
restaurants, food markets, in the school dining room
5. Realize the plate incubation in the lab/classroom
6. Realize the observations in the lab/classroom and analyze the results. They will be
recorded and organized in tables.
The points 2-6 will be performed as described in the following protocols.
7. Discuss with the whole classroom the results of each team. Make a whole table of results
that will centralize the results of all teams.
8. Investigate on the bases of the records made in the tables and the knowledge gathered
during the theoretical classes:
o The migration pathways of microbes during food handling
o The factors influencing their precence and migration
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
15
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
o The human actions that can influence microbes’ migration and food contamination.
1. Identification of the presence of microbes in air
Equipment and materials:
o Sterile Petri dishes
o Sterile microbial culture media (nutritional-agar or malt mash – agar)
o Loupe
Procedure:
 Firstly establish the sampling points. The sampling points are chosen according our interest
(in the proximity of food products, points of air admision (windows, doors), points with
human proximity or circulation, following the pathway of food handling, etc.) (Exp. near
the food preparing table in the kitchen, window, door, outdoor; supermarket, street, food
serving place outside home; in the classroom, in the school hall, in the school yard, etc.)
Distribution of
the liquefied
growing medium
Solidification of
the growing
medium
Incubation of the Petri
dishes at room
temperature
Sedimentation of the
microbes from air
Observation of
the microbes’
presence
The procedure of identifing microbes from air by
sedimentation on growing media


Prepare the sampeling dishes:
o Sterilese the Petri dishes and microbial culture media
o Liquefy the culture media in a water bath
o Distribute the liquefied culture media in Petri dishes. In each dish put media until
cover its bottom with a layer of 2-3 mm. Prepare a dish with culture media for each
sampeling point
Realise the sampling:
o Open the petri dishes
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
16
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931


o Expose the growing medium from each dish for 5 minutes to the contact with air by
removing the cover of the Petri dish. The microbes from air will fall by gravity
(sediment) on the surface of the growing medium
o Close the dishes by covering them
o Note the sample code (exp. the location of the sampling point) on the cover of the
Petri dish to identify the sample after incubation.
Grow the microbes by incubating the dishes at room temperature (20-25oC) for 7 days. The
microbial cells will multiply and generate colonies that can be observed and counted
After this period notice the appearance of the opaque points on the surface of the growing
medium. Use a loupe to magnify the image of these points.
Interpretation of the results
Before incubation the surface of the culture medium put on the Petri dishes was smooth. After
incubation it can be observed many opaque points on the surface of the medium. These points are
colonies of microbes. They can have different sizes, colours, forms and consistency. The colonies
indicate the presence of microbes in the air because each colony is grown from a microbial cell
that sedimentated on the suface of the medium during sampling.
colonies
Microbial colonies developed on the surface of the culture medium in Petri dishes
2. Identification of the presence of microbes on different surfaces and objects related to
food
Equipment and materials:
o Sterile Petri dishes
o Sterile microbial culture media (nutritional-agar or malt mash – agar)
o Sterile swaps
o Bottle with sterile water
o Loupe
Procedure
 Firstly establish the sampling points. The sampleing points are chosen according our
interest (different surfaces and objects related to food like tables where we prepare and
serve the meal, dishes, eating utensils, coking pots, etc.)(Exp. table where we prepare the
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
17
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931



food, table where we eat, serving dish; uncleaned table, cleaned table; eating tabel,
serving dish, fork, spoon, ect.)
Prepare the sampeling dishes according the previous described protocol
Realise the sampleing and insemination on the growing medium:
o Take a sterile swab and moisten it in sterile water.
o Scrap with the mostened swab on the surface of the object you will analise if there
are microbes on it. The microbes from the surface will adhere on the swab. Used a
new moistened swab for each sampling point. Scrap the same area on all sampeling
points in order to compare their microbial load.
o Open the Petri dishes by removing the cover
o Brush the surface of the growing medium from the Petri dish with the swab. The
brushing path had to cover the whole surface of the dish by parallel routes. The
microbes will be relised from the swab on the surface of the growing medium along
the brushing route. Make the some kind of brushing route in all dishes.
o Close the dishes by covering them.
o Note the sample code (exp. the location of the sample) on the cover of the Petri
dish to identify the sample after incubation.
Grow the microbes and observe the microbial colonies grown on the surface of the
medium according the previous described protocol.

Estimate the microbial load of the analised surfaces by observing the number and size of
the developed colonies.
Interpretation of the results
The apearance of opaque points on the surface of the growing medium indicates the presence of
microbes on the surface of the analised objects. To see them better usea magnification loupe.
Each colony is grown from a microbial cell that was removed from the suface of the analised
sampling point. The colonies have different sizes, colours, forms and consistency because they
belong to different kinds of microbes.
In different dishes there can be more or less colonies grown according with the cells they generate
them. The dishes with more small colonies indicates a higher microbia load of the sampling point
than dishes with a few amount of larger colonies.
Analising the presence and relative amount of microorganisms observed on different sampeling
points we can gather information on:
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
18
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
o The distribution of microbes on different locations (make a discution on this)
Few
colonies
Many
colonies
A lot of
colonies
Very few
colonies
Many
colonies
Different amounts of microbial colinies developed on the surface of the culture medium in Petri
dishes 1
3. Identification of the presence of microbes on our hands
Equipment and materials:
1
http://image.frompo.com/ea6a13561ec23a3baea65190f697a60e
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
19
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
o
o
o
o
o
o
A very clean small water basin to immerse our hands
Sterile water
Sterile swaps
Sterile Petri dishes
Sterile microbial culture media (nutritional-agar or malt mash – agar)
Loupe
Procedure
 Prepare the sampeling dishes according the previous described protocol
 Design the experiment – chose three students: 1) one that washed hands with soap and
warm water, 2) one that washed them only in warm water, and 3) one that does not
washed at all.
 Realise the sampling and insemination on the growing medium for each sthdent:
o Take a water basin and fill it with sterile water
o Imerge hands and shrub them. The microbes from hands will be removed and
suspended in the water from the basin.
o Take a sterile swab and moisten it in the water where you washed your hands.
o Open the Petri dish by removing the cover
o Brush the surface of the growing medium from the Petri dish with the swab as
described in the previous procedure.
o Close the dish by covering it.
o Repeat the procedure of removing microbes from your hands and inseminate them
for each student
Wash
hands
Moisten
the swab
Inseminate the
plate
Incubation of
the plate
Observation
of microbes’
presence
The procedure of identifing microbes from
hands
o Note the sample code (washed hands with water and soap / washed hands only
with water / not washed hands) on the cover of the Petri dish to identify the sample
after incubation.
 Grow the microbes and observe the microbial colonies grown on the surface of the
medium according the previous described protocol.
 Estimate the microbial load of the analised surfaces by observing the number and size of
the developed colonies.
Interpretation of the results
Microbial colonies will apear on the surface of the growing medium from the Petri dishes as
opaque points. Each colony is grown from a microbial cell that was removed from the suface of
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
20
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
your hands. The colonies have also here different sizes, colours, forms and consistency because
they belong to different kinds of microbes.
In the dishes are a different number of colonies.
Start from the event that without washing the hands there are much more microbes on the hand
than after washing them with warm water and with warm water and soap. Test if the colonies
developed in the dish belonging to the sample inseminated before and after washing the hands
are consistent to your hypothese, respective:
 Before washing – many small colonies
 After washing only with warm water – few larger colonies
 After washing with warm water and soap – fewer large colonies
Make a discution on the importance of washing hands in order to remove microbes from them
and why it is so important for food safety. Discuss also the importance of using soap.
4. Identification of the presence of microbes on different food products
Equipment and materials:
o Sterile Petri dishes
Moisten
the swab
Scrap the Insemination on
the medium
surface
Incubation of
the dishes
Observation
of microbes’
presence
The procedure of identifing microbes from
foods
o
o
o
o
Sterile microbial culture media (nutritional-agar or malt mash – agar)
Sterile swaps
Bottle with sterile water
Loupe
Procedure
 The procedure is similar to that described in the case of analysing the microbial load on
different surfaces.
 The diference consists in chosing the sampling points. These are different food products
chosen according our interest (Exp. surface of a package of a food product / the food
product removed from the pakage; fruits before and after washing them, crackers sold in
package / sold not packaged; etc)
Interpretation of the results
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
21
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
The observation of the microbial grow is also similar to the previous made description. There can
be observed colonies developed on the plates, that are evidence for the precence of microbed on
food products. The number of colonies grown on the plates are compared and if possible counted.
Analising the presence and relative amount of microorganisms observed on different food
products we can gather information on:
o The precence of microbes on food
o The difference of the microbial load according the food handling hygiene (washed / not
washed fruis, packed / not packed crackers, etc.) (make a discution on this)
5. Investigation on the migration pathways of microbes by handling
Equipment and materials
o The plates with grown microbial colonies on the surface of the growing medium.
o The observations and discussions made if analyzing:
 the presence of microbes in the environmental air
 the presence of microbes on different surfaces and objects related to food
 the presence of microbes on our hands
 the presence of microbes on food
Procedure
 Organize and draw a table with the following structure:
Location
(air, surfaces, hands,
food)
Sampleing point
(chosen according
the investigation
interest)
Sampeling point 1
Sampeling point 2
Sampeling point 3
Sampeling point 4
Sampeling point ….n
Estimated
microbial load
(few, many, a
lot of)
Observations

Register the observations made during the field activity and in the lab in the previous
presented table
 Make a location scheme of the food pathway. Insert to each location point the made
observations
 Draw the flow direction from each point to the folowing
Interpretation of the results
According the analyze of the inscriptions on the location scheme of the food pathway we can
establish:
o The distribution of microbes in different locations
o The migration pathways of microbes by food handling
o The direction of microbial migration
There can be refered differences and can be made interpretation on the potential couses of food
contamination and potential food born illness
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
22
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
6. Investigation on the environmental factors influencing the presence of microorganisms
and their migration
Equipment and materials
o The table with the centralized results of observations realized by all students`
teams.
o The location scheme of the food pathway with the inscription of the microbial
dinamics between the different analyzed locations.
Procedure
 Insert at each sampleing point in the location scheme the environmental factors you
consider that act here, according the knowledge gathered during the theoretical classes.
Interpretation of the results
According the knowledge in the field of food microbiologiy make interpretation on:
o What factors can determine the presence and amount of microbes at each location
(exp. the proximity of soil, waste water, animals, plants, human, lake of hygiene,
adulterated food, etc.)
o What factors can determine the migration of microbes from one location to the
other along the food pathway (exp, gravity, air fllow, direct contact, etc.)
o Haw can we prevent food contamination at each analysed sampling point
(managing the environmental factors that can interfere).
7. Investigation of human actions that can influence microbes’ migration and food
contamination.
Equipment and materials
o The table with the centralized results of observations realized by all students`
teams.
o The location scheme of the food pathway with the inscription of the microbial
dinamics between the different locations.
Procedure
 Insert at each sampleing point in the location scheme the human handeling related factors
you consider that act here, according the knowledge gathered during the theoretical clsses.
Interpretation of the results
According the knowledge in the field of food microbiologiy make interpretation on:
o What human related factors can determine the presence and amount of microbes
at each location (exp. lake of personal and handeling hygiene)
o What human related factors can determine the migration of microbes from one
location to the other along the food pathway (exp, direct contact with the food of ill
persons, lake of personal and handeling hygiene)
o Haw can we prevent food contamination by human handeling at each analysed
sampling point (personal and food handeling hygiene rules).
References
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
23
Let’s make it better!
Raising the awareness of the triad
nutrition-health-food safety in school education
Project No: 2014-1-RO01-KA200-002931
Nicolescu C., Enache C. – Practicum de microbiologie, vol.1. Tehnici uzuale, ED. Printech Bucuresti,
2000.
http://image.frompo.com/ea6a13561ec23a3baea65190f697a60e
This project has been funded with support from the European Commission. This presentation
(communication) reflects the views only of the author(s), and the National Agency and
Commission cannot be held responsible for any use which may be made of the information
contained therein.
EDU FOR HEALTH. PROMOTING HEALTHY EATING HABITS – TOPIC 10
24