Download Food Safety Disease – it is any harmful change in the tissues and/ or

Food Safety
Disease – it is any harmful change in the tissues and/ or metabolism of a plant, animal or
human that produces the symptoms of illness.
Pathogens – these are microorganisms that cause a disease (bacteria, yeasts, moulds, viruses
& protozoa).
Food poisoning
- Ordinarily the term is applied to diseases caused by microorganisms including both
illness caused by the ingestion of toxins elaborated by microorganisms & these
resulting from infection of the host through the intestinal tract.
- It can be a result of either chemical poisoning or ingestion of a toxicant (intoxication)
- Bacterial food intoxication – refers to food-borne illness caused by the presence of a
bacterial toxin formed in food.
- Bacterial food infection – refers to food borne illness caused by the entrance of
bacterea into the body through ingestion of contaminated foods & the reaction of the
body to their presence or to their metabolites
- Food poisoning – can be defined as an acute (arising suddenly & of short duration)
gastroenteritis caused by ingestion of food.
- Gastroenteritis – a disease of intestinal tract characterised by
i.
Abdominal pain
ii.
Diarrhoea
iii.
With/without vomiting
iv.
With/without fever
- Apart from their ability to cause gastroenteritis other features that are normally
considered to be characteristics of food poisoning organisms are;
1. Have the capacity to reproduce in food
2. Very large numbers are required to produce an illness although there are
exceptions. E.g. in some Salmonella serovars the number of bacteria required to
produce infection are low. However numbers required to produce illness may also
depend host resistance for a wide range of organisms.
3. Organisms causing food poisoning originate from animal sources of the
environment in general.
- Some authors exclude food borne illness that are caused by primary human pathogens
(that are adapted to human host) from their definition of food poisoning.
- These diseases have low infective doses i.e. only small amounts numbers of
organisms are required to cause infection.
- They are carried easily from one human to another, from the environment in general
or via faecal contamination from other humans.
- The most common infection source is water e.gs. Include Typhoid fever – Salmonella
typhi, Dysentery - Shigella dysentriae & Cholera – Vibrio cholerae.
- Some pathogenic strains of E. Coli can be included in this category
- Food borne diseases caused by viruses can be included in this category as viruses do
not multiply in food but food simply acts as a passive carrier for organisms.
-
This also applies to certain food-borne protozoal infections e.g. dysentery caused by
Entemoeba histolytica
Intoxications
- These involve food in which the organism grows in the food and releases a toxin from
the cells
- Toxin – a poisonous substance produced during metabolism & growth of certain
microorganisms & some higher plants & animal species / a poisonous substance
produced by living cells or organisms (Although human beings are technically living
organisms, artificial substances they make are not included.)
- when ingested along with food the toxin gives rise to the food poisoning syndrome
- the presence of the organism is irrelevant to disease production
- it is the toxin that give rise to the disease
- bacterial intoxications are either enterotoxins (affecting the gut e.g. as in disease
caused by Staphylococcus aureus) or neurotoxins (affecting the nervous system as in
botulism caused by Clostridium botulinum)
- Mycotoxicosis – disease produced by the ingestion of food containing mycotoxin
produced by mould fungi & diseases produced by algal toxins that find their way into
shellfish can also be considered intoxications
- Generally intoxications have short incubation periods
Infections
- These involve food poisonings caused by the ingestion of live organisms when,
typically the organisms grow in the GI tract to produce the disease.
- Most food poisoning caused by microorganisms fall into this category e.g.
Salmonellosis.
- Enteritis associated with food infections is due to the production of exotoxins that act
as enterotoxins
- Enteritis – inflammation of the intestines especially small usually characterised by
diarrhoea.
- Exotoxin – a toxin that is secreted by microorganisms into the surrounding medium
which can cause damage to host by destroying cells and disrupting normal cellular
metabolism.
- Endotoxin – a toxin that is confined inside the microorganism and is released only
when the microorganism is broken down or dies.
- In some types of food poisoning e.g. Clostridium perfringens live cells need to be
ingested for the diseases to occur but the organism does not grow and reproduce in the
gut.
- Vegetative cells sporulate after ingestion and an enterotoxin is released when the
spore mother cells breakdown releasing the spores.
- Because living cells need to be ingested to cause this type of food poisoning it can be
considered as a food infection.
- NB – not all infections lead to enteritis.
- The live organisms that are ingested may pass the gut mucosa into the vascular system
and invade other body tissues e.g. Listeria monocytogenes & Mycobacterium
tuberculosis
Characteristics of Microorganisms
Some are unicellular some are multicellular.
1. Hydrogen Ion concentration (Ph)
- Microorganisms are significantly affected by pH because they have no mechanisms to
regulate ph
2. Moisture requirement
- Microorganisms have an absolute demand for water for without water no growth can
occur.
- Water is made unavailable in various ways
i.
Solutes & ions tie up water in solution (increase [c] of solutes)
ii.
Hydrophilic colloids (gel) make water unavailable. As little as 3-4% agar in a
medium may prevent bacterial growth by leaving too little available moisture.
iii.
Water of crystallization/ hydration is usually unavailable to microorganisms
e.g. ice.
3. Oxidation – Reduction Potential
- The oxygen tension or partial pressure of oxygen about a food and the O-R potential,
or reducing and oxidising power of the food itself influences the type of organisms
which will grow & hence the change produced in the food.
- A high O-R potential favours aerobes but will permit the growth of facultative
organisms.
4. Nutrient content
i.
Foods for energy – CHO especially sugars but other carbon compounds may
also serve e.g. esters, alcohols, peptides, amino acids, & organic acids & their
salts.
Complex CHO such as cellulose & starch can be utilised by comparatively
few microorganisms.
Many MOs can’t destroy lactose hence they do not grow well in milk.
ii.
Foods for growth – most MOs cannot hydrolyze proteins & hence cannot get
nitrogen from them without the help of proteolytic organisms.
iii.
Accessory foods/ Vitamins – some MOs are not able to manufacture some or
all of the vitamins needed & must have them furnished.
Most natural plant and animal food stuffs contain an array of these vitamins
but some may be low in amount or lacking e.g. meats are high in B vitamins &
fruits are low but high in ascorbic acid. Egg white contains biotin but also
contains avidin which ties up biotin making it unavailable to microorganisms.
 Thermophiles
 Thermoacidophiles
 Methanogen
 Halophiles
 Acidophiles
 Mesophiles
 Aerobes
 Anaerobes

Facultative anaerobes
Naturally Occurring Toxic Substances
 For Animals Refer to hand out
Plants
Toxin
Protease
Chemical nature
Protein
Food source
Cereals, beans,
potatoes
Haemoglutanins
Protein
Beans, lentils, peas
Saponins
Glycosides
Soybeans, spinach,
potatoes, peanuts
Cynogens
Cygenic in nature/
glycosides
Antibiotic
Pulses, peas,
cassava, flaxbeans
Mushrooms
Aflatoxins
Symptoms
- Impaired growth
and food
utilization
- Agglutination of
erythrocytes
- Impaired growth
and food
utilization
- Headaches
- Haemolysis of
erythrocytes
- Cynic poisoning
- Acidosis
- Vomiting
- Running stomach
till death
- Diarrhoea
Food Additives
These are added to food for one of the following reasons
a. To maintain the nutritional quality of food
b. To improve the keeping qualities of food
c. To make food more attractive
d. As an essential aid to food processing
e. To preserve them from decay & spoilage
f. To improve the keeping qualities of food during food distribution
g. To improve or enhance the flavour, color & texture of a food to make more
acceptable
h. To produce a uniform food product during large scale manufacture
i. To provide easy-to-prepare convenience foods in a society that is busy & spends
less time in the kitchen than in the past.
Important requirements of food additives
For an additive to be acceptable for use in a food it must conform to certain principles;
-

It must be safe to use

It must be effective in its intended use

It must only be used in the minimum quantity required for it to work

It must not mislead the consumer about the nature & quality of a food

It should where possible be of nutritional value to the body
Food additives maybe;

Natural substances – those which have been produced biologically & have
been extracted from natural products e.g. lecithin from soya beans.

Synthetic compounds – those which are nature identical. These are
synthesised either chemically or biologically to match naturally occurring
counterparts e.g. L-Ascorbic acid which matches Vitamin C

Artificial compounds – these are synthesised chemically & have no naturally
occurring counterparts e.g. arzodicarbonamide which is used as a flour
improver. It does not occur naturally but is synthesised chemically.
Additive
Use
Foods involved
Example
Acids
make flavors "sharper",
and also act as
preservatives and
antioxidants
Beverages, fruit
juices.
Vinegar, citric
acid, tartaric
acid, malic
acid, fumaric
acid, and
lactic acid.
Acidity regulators
change or otherwise
control the acidity and
alkalinity of foods
Anticaking agents
keep powders from caking
or sticking
Antifoaming agents reduce or prevent foaming
in foods
Antioxidants
inhibit the effects of
oxygen on food
Bulking agents
increase the bulk of a food
without affecting its
nutritional value
Food coloring
replace lost colors or make
food look more attractive
Color retention
agents
used to preserve a food's
existing color
Emulsifiers
allow water and oils to
remain mixed together in
an emulsion
Flavors
give food a particular taste
or smell
Flavor enhancers
enhance a food's existing
flavors
Flour treatment
agents
improve its color or its use
in baking
Glazing agents
provide a shiny appearance
or protective coating to
foods
Humectants
prevent foods from drying
out
Tracer gas
allow for package integrity
testing to prevent foods
from being exposed to
atmosphere, thus
guaranteeing shelf life
Preservatives
prevent or inhibit spoilage
of food
Stabilizers
They help to stabilize
emulsions.
For flavoring.
Sweeteners
Thickeners
increase viscosity without
substantially modifying its
other properties
GRAS means Generally Regarded As Safe
Hazard Analysis Critical Control Point (HACCP)
It is a systematic, preventative approach to food safety & pharmaceutical safety that
addresses physical, chemical and biological hazards as a means of prevention rather than
finished product inspection.
- It is used to identify potential food safety hazards so that key actions known as critical
control points (CCP) can be taken to reduce / eliminate the risk of the hazard being
realised.
- Hazard – anything associated with the food that has potential to cause harm to
consumer or the product. This can mean;
 Unacceptable contamination, growth or survival of food spoilage organism
 Presence of a microbial toxin
 Unacceptable contamination, growth or survival of food poisoning organism
 Presence of a microbial enzyme that can cause spoilage
- A hazard may occur @ any stage of the production line. (i.e. during raw material
production, manufacturing, distribution, retailing or consumer use)
NB – Not all hazards are microbial. A hazard may be chemical such as the presence of
pesticide residues or physical e.g. presence of foreign body.
- Critical Control Points – these are steps / procedures that can be identified during raw
material production, manufacturing, retailing, distribution or consumer use in which
hazards can be controlled.
- Identifying CCPs focuses attention on specific prevention and control measures.
- According to ICMSF, there are two types of CCPs
- ICMSF –
a. Those that will assure the control of a hazard
b. Those that will minimise a hazard but cannot assure its control e.g. thermal
processing of canned low acid foods (i) & correct container handling after
processing (ii).
- Risk – the likelihood of a hazard occurring. It is often ranked as low, medium or high
- Severity – a level of danger presented by a hazard. A risk can be very low & the
severity high e.g. the risk from bovine tuberculosis in milk produced by the modern
dairy industry is extremely low as a result of the attested hard scheme and
pasteurisation. The severity of the disease if it did occur is however high.
- Monitoring – it involves checking whether a CCP is under control. This can involve
visual inspection, smell physical measurement, chemical measurement or
microbiological testing.
- It should detect any loss of control over a CCP in time for corrective action to be
taken before there is a need to reject the product. This means because of the time lag
involved in producing results, microbiological tests are normally associated with
verification rather than monitoring.
- Monitoring is sometimes given a wider interpretation when shelf – stable products
e.g. canned food, UHT, milk & frozen foods can be held before release until the
results of microbiological testing are available.
Verification – it is the application of tests that are additional of those used for
monitoring
- It determines whether the HACCP is operating correctly e.g. Chlorine levels in can –
cooling water can be monitored to ensure that levels of contamination are kept to an
acceptable level and do not cause post process recontamination resulting in
unacceptable levels of leaker spoilage.
- Incubation tests can be carried out on cans to verify that post process recontamination
has not taken place.
Stages in setting up HACCP
- Setting up an HACCP requires consideration of the following
 Raw materials
 Each stage of manufacturing process
 The distribution system
 Retailing
 Education of the workforce
 The target consumer
 The way in which the consumer is likely to handle the product in relation to
hazard or risk
 Monitoring & verification
-
Identify HACCP team (food technologists, engineers, etc.)
Construct process flow diagram
Identify hazards, Asses severity or risk
Identify CCPs
Specify criteria for CCPs (e.g. pasteurisation temperature)
Set tolerances for CCPs (UL & LL)
Establish monitoring system for each CCP (visual, sensory etc)
Establish plan for corrective action
Establish procedures for verification (confirmatory tests)
Establish system for documentation & recording
Establish procedure for review
Principles of HACCP

Conduct a hazard analysis

Identify CCP

Establish critical control limits

Establish CCP monitoring requirements

Establish corrective action

Establish record keeping procedures

Establish procedures for assuring HACCP is working as intended
Food Compositions
 Water
 Proteins
 Carbohydrates
 Fats / lipids
Solution & Dispersions
- Nearly all foods contain water
- Nutrients present in these foods are dispersed in water.
- Solids, liquids & gases may be dispersed in water to form either solutions/ colloids
Solutions
- It is made up of two components; the solute which is the substance dissolved & the
solvent, the liquid in which the solute is dissolved
- Solutions are not necessarily composed of a solid dissolved in a liquid
- Soda water is a solution of a gas (CO2) dissolved in liquid water
- Vinegar is a solution of one liquid acetic acid dissolved in 2nd liquid water.
- Dissolved substances cause an increase in a boiling point & a depression of freezing
point of solutions.
- The effect of a solute on boiling point & freezing point of a solution is directly
proportional to its concentrations
- Solutions are formed by inorganic compounds in which the particles or ions have an
affinity of water.
- If the particles of a compound have a greater attraction for each other than they have
for water the compound will be insoluble.
- Mineral elements found in foods such as sodium & chlorine are usually present as
ions & form true solutions.
- Small organic molecules such as sugars which have an affinity for water also form
true solutions.
- Vitamins depending on their structure maybe either dissolved in water or in the fat
present in foods.
Solubility
- It is the extent to which the substance will dissolve in a given solvent
- It is expressed as g solute pre 100ml solvent
- Solubility of must substances increase with increase in temperature
- Saturated solution – is one in which no more solute will dissolve in the solvent @ a
given temperature.
- Supersaturated solution – it is a solution that contains more dissolved solute than a
saturated solution. (It can be obtained by cooling a saturated solution). However it is
unstable & the excess dissolved solvent will readily revert to the solid form by
fermentation of crystals.
- Crystallization – under normal circumstances when a saturated solution is cooled
particles of the solute will be disposed from the solution.
- The particles of the solid will assume a characteristic geometrical shape and are
known as crystals.
Colloids – if a substance such as albumin the protein in egg white is mixed with water
it does not dissolve but forms a colloid dispersion.
- The dispersion is not a solution neither is it homogenous since the proteins do not
dissolve.
- The molecules are dispersed throughout the water producing a heterogeneous/ two
phase system, with disperse & continuous phase.
- Due to gravity the particles of the disperse phase will settle out as a sediment after a
period of time.
Types of colloidal System
Common Name Disperse Phase Continuous Phase Examples
Foam
Gas
Liquid
Beaten egg white, whipped
cream, ‘Head’ on beer
Solid foam
Gas
Solid
Bread, Cake
Emulsion
Liquid
Liquid
Milk, Cream, mayonnaise
Gel
Liquid
Solid
Jelly, Baked egg custard
Gel
Solid
Liquid
Egg white
- Most colloidal dispersions are stable but 2 phases may separate out over a long period
of time with rate of separation accelerated by an increase in temperature or by
mechanical agitation.
- Many colloids separate out on freezing
- Liquid based colloids can be categorised into 2
1. Lyophillic colloids – in which there is an attraction between the colloidal
particles (disperse phase) and the liquid of the continuous phase e.g. sols &
gels.
- If the continuous phase is water the colloids are said to be hydrophilic
2. Lyophobic e.g. emulsions (opposite of Lyophillic)
Sol & Gels
- The proteins & starch in food may be present in the form of sols & gels
- Each amino acid has a side chain which is basically a hydrocarbon chain but which
may contain an amino group or a carboxylic acid group.
- Hydrogen bonding may take place between the water molecules & the peptide links or
between the water molecules, the amino and carboxyl groups on the side chain.
- The protein can be readily dispersed in the form of a colloid because of the attraction
between parts of the protein chain & the water.
- Starch consist of long chains of glucose units & contain many hydroxyl groups which
can form hydrogen bonds with water molecules, therefore starch can form a colloid.
-
-
When a jelly is made, gelatine (a protein) is dispersed in water & heated forming a
sol.
There is little attraction between the protein molecules and the sol behaves like a
liquid, i.e. it is runny & can easily be poured.
On cooling the molecules are compact and coiled in the sol, begin to unwind & cross
links are formed between adjacent molecules & a mesh or network is formed.
The sol has been converted to a gel & a gel resembles a solid rather than a liquid.
-
Sometimes gel formation can be reversed e.g. if a jelly is heated it liquefies & forms a
sol.
- Cornstarch is used as a thickening agent since they are both capable of forming sols &
gels.
- Synerisis – is the shrinkage of a gel & subsequent loss of liquid.
- This may take place if a jelly is left to stand for a long time.
Emulsions
There are 2 main types usually found in food.
1. Oil – in – water e.g. milk, cream, mayonnaise, salad cream, ice cream
2. Water - in – oil e.g. butter, margarine, egg yolk
There are 3 ways in which emulsions may break down.
1. Separation into 2 phases. This may be caused by;
a. Adding a disperse phase too quickly during preparation
b. Action of heat
c. Action of acid, i.e. lowering the pH.
d. Freezing
e. Adding too much disperse phase during preparation (max disperse is about 74%)
2. Separation into 2 emulsified layers e.g. formation of cream layer in milk
3. Phase inversion – the disperse phase become the continuous phase & vice versa. This
occurs in forming butter from cream & is caused by mechanical agitation
Foams
- Consists of very small bubbles of a gas usually air dispersed in a liquid.
- It is the action of substances dissolved in the liquid which stabilizes the foam since
the dissolved substances reduces the surface tension of the liquid & prevent the
molecules of the liquid from massing together.
Heat Transfer in Cooking
-
Heat energy can be transferred from one point to another.
The principle behind cooking relies on the movement of heat from the cooker to the
food at suitable rate.
 Conduction – this is whereby solid molecules around the heat source vibrate rapidly
as they receive heat energy.
- The vibration is transferred to the next molecules in contact thereby the whole
surface/ object consequently.
 Good conductors – they conduct heat rapidly & efficiently e.g. copper, silver,
brass, aluminium, iron
 Poor conductors (heat insulators) – opposite to the above. E.g. glass, plastic,
wood, cotton cloth, wool, still air.
Examples of conduction & Insulation in food preparation
 Oven – insulated with glass fibre/ a similar poor heat conductor to prevent heat loss.
 Oven glass – made of thick insulating material to prevent heat conduction
 Pans – metals (good conductors)
 Pan handles – insulating material e.g. plastics
 Double based cake tins – layer of air prevents rapid heat conduction & reduces risk of
burning.
 Cooler boxes – insulators
 Food e.g. meat is a poor conductor.
 Convection – it involves gases & liquids (poor conductors)
- Heated molecules expand & rise thus allowing heavy molecules from the cooler part
to fall.
- In this way convection currency are set up until a constant temperature is reached.
Examples
 Baking / roasting oven
 Boiling
 Steaming
- Semi – liquid/solid mixtures e.g. sauces have slow convection currency because they
have less fluid hence if not stirred whilst being heated they burn @ the base as the
heat is not carried away fast enough.
 Radiation – heat can pass from one point to another without the aid of a medium
(molecules) & passes through space/ a vacuum. This is possible because of the
existence of electromagnetic waves of which there are several types including X –
rays, light waves, heat waves & microwaves
- Heat rays are called infra – red rays & when they come into contact with an object
some of them are absorbed & are felt as heat, while others are reflected.
- The space between object and & the source of the heat rays is not heated.
- Dull black surfaces absorb & emit heat rays well.
- White shinny surfaces reflect & do not emit them well.
Examples