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Food Safety and toxicology
Aims
To explain the causes and effects of
food poisoning and its relevance to
food safety
Basically, food is a mixture of chemicals. Usually, food
components are distinguished in four categories:
1.nutrients,
2. toxins of natural origin,
3. contaminants,
4. and additives.
The nutritients account for more than 99.9% of the food.
The main classes of nutrients are :
carbohydrates, proteins, fats, vitamins, and minerals,
and all of them may pose toxicological risks to the
consumer.
Food Borne diseases
Poisoning
Infections
Chemical poisoning
intoxication
poisonous
Plant tissue
poisonous
animal tissue
Algae toxins
mycotoxins
Enterotoxins
neurotoxins
enterotoxigenic
invasive
microbial intoxications
bacterial toxins
toxic metabolites
interactions with carbohydrate
metabolism
What are Food-Borne Diseases?
People get sick with a food-borne disease when they
consume foods or beverages contaminated with
disease-causing microbes, chemicals, insects or other
harmful substances.
Bacteria, viruses and parasites cause most of these
diseases. Toxins, poisons and chemicals can also
contaminate food and cause illness.
Food Safety
• Harmful substances in foods
Pathogens
• Bacteria, viruses, parasites
• Some common pathogens causing foodborne illness
– Staphylococcus aureus, Clostridium botulinum,
Salmonella, Escherichia coli
Chemical contamination
• Pesticides
• Animal drugs
• Pollutants
Natural toxins
• Methyl mercury
• Poisonous plants
• Solanine
Perceived Risk from Food:
% Viewing as a Serious Hazard
Major social impact of food
borne disease…
• Lost productivity time
– Days work/school
– Financial impact
• Risk of mortality
• Risk of transmission to family and
others
The Food Pathogen Problem
• Estimates of foodborne disease in
U.S./yr:
–
–
–
–
–
6.5 to 33 MILLION foodborne illnesses
Up to 9,000 deaths
Hospitalization costs -- > $3 billion
Lost productivity -- > $9 billion
Under-reported!
Adapted from: Council for Agricultural Science and Technology. Foodborne
Pathogens: Risks and Consequences, 1994.
FDAs Rank of Areas of Concern
Most Dangerous
1. Microbial food illness
2. Naturally occurring toxins in foods
3. Residues in foods
– Environmental contaminants
– Pesticides
– Animal drugs, such as hormones, antibiotics
4. Food processing and nutrients in foods
Least Dangerous
5. Intentional Food Additives
6. Genetic modification of foods
Most food poisoning is caused by?
Bacteria
Microbes and Food Safety
Symptoms of foodborne illness
– Diarrhea of more than 3 days’ duration
– Fever of longer than 24 hours duration
– Headache accompanied by muscle stiffness and
fever
– Numbness, muscle weakness, tingling sensations
in the skin
– Rapid heart rate, fainting, dizziness
Majority of food-poisoning cases
– Result of errors consumers make in handling
foods after purchase
– Commercially prepared food is “usually” safe
Food Safety
– Raw meats can contain live, disease-causing
organisms
– Thorough cooking makes them safe
– In the mid-1990s a fast-food restaurant chain in
the Northwest served undercooked hamburgers
from meat contaminated with bacterium E. coli
0157:H7
• 4 people died
• 100s of patrons became seriously ill
As a result more Government Inspections and
Industry controls were set up through the
Hazard Analysis Critical Control Point
(HACCP) plan
In order to grow and multiply germs need:
Time
Moisture
Food
Warmth
Flies
Waiting
Remember it like this
Too
Many
In ideal conditions where there is
Moisture, Food and Warmth
(37degrees centigrade is ideal),
bacteria can double every 10 to 20
minutes. They do this by dividing
in to two. This is called
Binary Fission
These cells are beginning to divide into two
After 10 minutes
After 20 minutes
After 30 minutes
After 40 minutes
cooking chicken to a core temperature
of 75°C should kill most of the bacteria
Time : 9.30
Bacteria : 0
Time : 9.40
Bacteria : 12,000
Time : 9.50
Bacteria : 24,000
Time : 10.00 Bacteria : 48,000
Time : 10.10
Bacteria : 96,000
Time : 10.20 Bacteria : 192,000
Time : 10.30 Bacteria : 384,000
Time : 10.40 Bacteria : 768,000
Time : 10.50 Bacteria : 1.5 million
From 0 to 1,536,000 in
only 80 minutes !!!!!!
Knife
contaminated
by blood
Bacterial Food Poisoning
• Because harmful microorganisms are
present everywhere in the environment,
any food can become contaminated if
not properly handled before
consumption.
Many foodborne pathogens are ubiquitous
in nature and generally found in
soil, water, animals and plants. Pathogens
are introduced into a processing
plant through the raw materials. Humans
and plant equipment may also bring
the organisms to a plant. Recontamination
of processed food also frequently
occurs and contributes to foodborne
outbreaks and illnesses. Pathogens can
survive for prolonged period on inanimate
objects and serve as a source.
Bacterial Growth Curve
Numbers
Of
Bacteria
rapid
multiplication
no multiplication
Lag Phase
Stationary Phase
Numbers of
bacteria remain
constant as the
number
produced is
equal to the
number dying
Time (hours)
Numbers of
bacteria
decrease
When considering a product safety, it is
important to know the type of microorganisms
or toxins likely to be present, their numbers,
and concentrations. In addition, their response
to the heat (heat-labile or heat-stable), pH,
salts, and other processing conditions is
important to consider.
The numbers and types of microorganisms
present in a finished food product are influenced
by :
•the original source of the food
•microbiological quality the raw or unprocessed
•sanitary conditions
•the conditions for subsequent packaging,
handling, storage, and distribution.
Fig. 19-4, p. 669
Bacteria and Temperature
100
HIGH
Minimum
Growth
Temp.
Campylobacter
Cl botulinum A&B
Staph aureus
E. coli
Salmonella
Cl perfringens
Listeria
Cl botulinum E
Bacillus cereus
LOW
LOW
HIGH
Bacteria die if heated
for a sufficient time.
The longer the time, the
greater the destruction
63
40
38
Heat resistance
• Pathogenic bacteria grow best at human body
temperature 37ºC. However the majority will grow
between 15-45ºC
• Non-sporing cells of bacteria are killed at
temperatures above 60ºC. The length of time
ranges depending on the organism
• Boiling kills living cells, but will not kill all
bacterial spores
• Fridges should be set below 5ºC. Some bacteria
such as Listeria monocytogenes can grow
at refrigeration temperatures
Bacteria
grow
quickly
Bacteria
grow
36
15
7
4
0
Bacteria stop growing,
but do not die
Bacteria
Grow
at slower
rate
Food Safety
• Food can provide ideal conditions for bacteria
to thrive or produce toxins
– Disease-causing bacteria require
• Warmth
40°F - 140°F = 4°C - 60°C
• Moisture
• Nutrients
• To control bacteria
–
–
–
–
Keep
Keep
Keep
Keep
hot food hot-above 140F
cold food cold-below 40F/4C
raw foods separate
your hands and the kitchen clean
Food Safety
• Keep Hot Food Hot
– Keep cooked foods at 140°F or higher until served
cooking does not destroy all bacterial toxins
– If handled improperly can cause illness
– Cooked foods should be refrigerated immediately or
within two hours at the maximum
• Keep Cold Food Cold
– Start when you leave the grocery store
– At home, put foods into the refrigerator or freezer
immediately
– When defrosting foods
• Thaw meats or poultry in the refrigerator
• Marinate meats in the refrigerator
Food Safety
• Food with an “off” appearance or odor should not
be used or tasted
• Keep raw foods separate /Prevent crosscontamination
– Raw foods, especially meats, eggs and seafood, are
likely to contain bacteria
– Keep the raw foods and their juices away from
ready-to-eat foods
– After handling raw foods wash surfaces & your hands,
thoroughly with soap
• Foods prone to microbial growth
– Those high in moisture and nutrients
– Those chopped or ground like meats and poultry
Foods That Make People Sick
• Eggs
– Raw, unpasteurized eggs are likely to be contaminated by
Salmonella bacteria
– Raw pasteurized egg substitutes may contain a few live
bacteria
• They may not be safe for pregnant women, the elderly, the very
young, or those suffering from immune disorders
• Raw Produce
– Fruits and vegetables are a microbial threat unless they
are thoroughly rinsed in running cold water
– Ten years ago, meats, eggs, and seafood posed the
greatest foodborne illness threat
– Today produce equals them
Know the Potentially Hazardous Foods
• Preparing and serving safe food is important
to your customers.
• Be careful when you work with and prepare
foods that are “potentially hazardous.”
– These are foods that have been linked to
foodborne illness
• Examples of potentially hazardous food are:
•
•
•
•
•
Meat, poultry and fish
Milk and egg products
Salads and sandwiches made with meat
Sliced melons and sprouts
Cooked vegetables, cooked rice or beans
You are responsible for identifying “potentially
hazardous” foods.
• Click below to reveal the “potentially hazardous”
Potentially
foods.
Hazardous
Contaminated
irrigation or
flood water
Human/animal
feces
Contaminated
seeds
Untreated manure
Staphylococcus
Aureus
Found in human
nose and throat
(also skin)
Salmonella
Found in animals,
raw poultry and
birds
Bacillus Cereus
Found in soil,
vegetation,
cereals and
spices
Clostridium
Perfingens
Found in animals
and birds
Clostridium
Botulinum
Found in the soil
and associated
with vegetables
and meats
The diseases caused by foodborne
pathogens can be classified into three
forms:
foodborne infection
foodborne intoxication
foodborne toxicoinfection
Toxic bacterial food poisoning
some bacteria grow in food and produce a
toxin within the food which is then consumed
e.g. Bacillus cereus and Staphylococcus
aureus. When the food is consumed viable
cells of the bacteria do not need to be
present.
Other microorganisms in food may
produce harmful or deadly toxins
while growing in the intestinal tract
e.g. Clostridium perfringens,
enterotoxigenic Escherichia coli and
enterohaemorrhagic E. coli
Infective bacterial food poisoning
infections occur when pathogens are
ingested via contaminated food and the
bacteria is established in the body,
usually growing inside the intestinal tract
and irritating intestines e.g. Salmonella
spp. and Campylobacter jejuni. The
infection may involve subsequent growth
in other tissues
Intoxication
Ingestion of preformed toxins such as
staphylococcal enterotoxin, botulinum toxin, Bacillus
cereus toxin, and seafood toxins results in food
poisoning or Intoxication.
Microorganisms present in foods will grow under
favorable conditions and produce toxins in the food.
Following ingestion, Toxins are absorbed through
the gastrointestinal epithelial lining and cause
local tissue damage and may induce inflammation
resulting in diarrhea or vomiting.
In some cases, toxins are translocated to distant
organs or tissues such as liver, kidney, peripheral,
or central nervous system where they can cause
damage.
Toxicoinfection
Some bacteria cause toxicoinfection, which occurs when
ingested bacteria first colonize the mucosal surface and
then produce exotoxins in the intestine.
Toxins can induce toxic effects on the local cells or
tissues and in some cases toxins enter blood stream
and induce disease. Examples include cholera toxin
produced by V. cholerae;
Clostridium produces hydrolytic enzymes such as
lecithinase (breaks down lecithin), hyaluronidase and
protease (break down extracellular matrix and disrupts
tissue structure)
Toxins
Some bacteria release poisons known as
toxins which cause food poisoning.
Some toxins, known as exotoxins multiply in
food. These toxins are not easily destroyed
by cooking and may remain in food once
they have developed.
Other bacteria produce toxins inside the
human body only after the food has been
eaten. These are called endotoxins
There are many types of exotoxins and they are
grouped based on the structure and the mode of
action
Membrane-disrupting toxin (pore forming):
These toxins either insert into the membrane to cause pore
formation (example, hemolysin)
A–B type toxin:
These types of toxins have two subunits; A and B. B binds to
cell receptor and A exerts enzymatic activity such as
inhibition of protein synthesis or cleavage of target protein.
Proteases:
Some toxins (i.e., neurotoxins) inactivate metalloproteases
(Zinc metalloprotease) action, thereby interfering with nerve
impulses.
Table Characteristics of
bacterial toxins
Toxin type Toxins
Producing
bacteria
Membrane Hemolysin
E. coli
damaging Listeriolysin O
L.monocytogenes
toxin
Perfringolysin O C. perfringens
-toxin
S. aureus
Streptolysin O
S. pyogenes
Inhibit
protein
(A–B type
Shiga toxin or
Shiga-like toxin
Diphtheria toxin
Edema factor
Shigella spp.
E. coli
C. diphtheriae
B. anthracis
Mode of action
Pore formation
Pore formation
Pore formation
Pore formation
Pore formation
Target
Plasma
Cholesterol
Cholesterol
Plasma
membrane
Cholesterol
N-glycosidase
28S rRNA
ADP ribosylation synthesis
Adenylate
cyclase
(i) A-B type toxin
receptor
Binding
B A Toxin
Enzymatic
action
(ii) Pore-forming hemolysin
(iii) Membrane active enzyme
Phospholipase cleaves
phosphatidylcholine(PC)
Salmonella
• Sources - The intestines of ill people
and carriers, animals and animal food,
raw meat, raw poultry, raw milk, raw
eggs, food pests
• Common food vehicles – Undercooked or
contaminated cooked meat, raw milk and
eggs
• Onset period – 6 to 72 hours (usually 12
to 36) Endotoxin in intestine (infective
food poisoning)
Salmonella
• Symptoms - Abdominal pain, diarrhoea,
vomiting and fever. Duration is usually one to
seven days.
• Specific characteristics – Usually requires
millions of bacteria to cause illness.
Multiplies from 5°C to 47°C under aerobic or
anaerobic conditions.
Aerobic and Anaerobic
• Bacteria which need oxygen to multiply are
classed as aerobic
• Bacteria which only multiply without oxygen
are called anaerobic
• Just to confuse you some bacteria including
Salmonella, Staphylococcus aureus and
Bacillus cereus are classed as facultative
anaerobes which means they can multiply with
or without oxygen!
Salmonella
•
•
•
•
•
•
•
Specific controls
Hygienic farm and abbatoir practices
Avoid cross contamination
Complete thawing of frozen poultry
Thorough cooking to 75°C for one minute
High standards of personal hygiene
Effective cleaning
Safe sewage disposal
Clostridium perfingens
• Sources - The intestines of humans
and animals, faeces and sewage, soil
food pests, raw meat and poultry
• Common food vehicles – Rolled joints,
casseroles, stews, sauces and meat
pies when cooking has removed
oxygen
• Onset period – 8 to 22 hours (usually
12 to 18) Enterotoxin in intestine.
(infective food poisoning)
Clostridium perfingens
• Symptoms - Abdominal pain, diarrhoea,
(vomiting is rare) and fever. Duration is
usually 12 to 48 hours.
• Specific characteristics – Usually requires
millions of bacteria to cause illness.
Multiplies from 10°C to 52°C under anaerobic
conditions. At 46°C it can double every 10
minutes. Produces spores. Illness caused
from consuming millions of organisms
Staphylococcus Aureus
• Sources - Human nose, mouth, skin,
hands, spots, boils, septic cuts etc
• Common food vehicles – Dairy
products. Cold cooked meat and
poultry, peeled cooked prawns
• Onset period – 1 to 7 hours (usually
12 to 18) Exotoxin produced in food.
(Toxic food poisoning)
Staphylococcus Aureus
• Symptoms - Abdominal pain, diarrhoea,
vomiting. Occasionally subnormal
temperatures. Duration between 6 and 24
hours.
• Specific characteristics – Usually requires
millions of bacteria to cause illness. Toxin may
survive boiling for up to 30 minutes. Multiplies
from 7°C to 48°C under aerobic or anaerobic
conditions. Can tolerate relatively high salt
content.
Endotoxins are part of the cell structure and are cell
associated, such as LPS in Gram-negative bacteria or PGN
and LTA in Gram-positive bacteria.
Some toxins such as cholera toxin and E. coli LT toxin, are
designated as enterotoxins because They are responsible for
enteric diseases (or gastroenteritis).
Cytotoxins are cell- or tissue-specific such as neurotoxins
(affect nerve cells), leukotoxins (attack leukocytes),
hepatotoxins (attack liver cells), and cardiotoxins (damage
cardiac tissue).
.
Toxin designation is sometimes based on the bacterial
species that produced them;
Cholera toxin is produced by Vibrio cholerae; Shiga toxin
by Shigella species,
Diphtheria toxin by Corynebacterium diphtheriae,
tetanus toxin by Clostridium tetani,
botulinum toxin by Clostridium botulinum.
Sometimes the toxin is named on the basis of the action it
exerts such as adenylate cyclase produced by Bordetella
pertussis,
lecithinase by each Clostridium perfringens and Listeria
monocytogenes.
Toxins may also be designated by a letter such as
staphylococcal enterotoxin A (SEA), SEB, SEE,
etc., by Staphylococcus aureus.
Endotoxin such as LPS, PGN, and LTA are responsible
for septicemia. The Lipid A component of LPS is highly
toxic. LPS raises the body temperature and activates
macrophages to produce IL-1 and TNF-α, which in turn
causes the hypothalamus to release prostaglandins.
Increased prostaglandin causes elevated body
temperature (fever). In essence, this defense strategy
is designed to inhibit bacterial growth.
Aspirin blocks prostaglandin release and thus reduces
body temperature. Endotoxins can trigger a massive
inflammatory response leading to septicemia and
septic shock. During septic shock, the circulatory
system collapses, blood pressure drops, fever
increases, heart rate increases, multiple organs fail,
and death follows.
Bacillus Cereus
• Sources - Cereals, especially rice,
cornflour, spices, dust and soil
• Common food vehicles – Reheated
rice, cornflour and spices.
• Onset period – 1 to 5 hours. Exotoxin
produced in food. (Toxic food
poisoning)
Bacillus Cereus
• Symptoms - Abdominal pain, diarrhoea,
vomiting. Occasionally subnormal
temperatures. Duration between 12 and 24
hours.
• Specific characteristics – Forms spores
which produce an exotoxin under aerobic or
anaerobic conditions. Both the spores and
toxin will survive normal cooking
temperatures. Millions required to cause
illness. Bacteria multiply between 7°C and
48°C.
Clostridium Botulinum
• Sources - Fish intestine, soil and
vegetables.
• Common food vehicles – Low acid
processed food contaminated after canning
or vacuum packing. Smoked fish, bottled
vegetables.
• Onset period –2 hours to 5 days (usually 12
to 36 hours). A heat sensitive neurotoxin
produced in the food which affects the
nervous system. (Toxic food poisoning)
Clostridium Botulinum
• Symptoms - Difficulties in swallowing, talking
and breathing. Double vision and paralysis.
Diarrhoea followed by constipation. Fatalities
are common and survivors may take several
months to recover.
• Specific characteristics – Forms spores
which produce an exotoxin under anaerobic
conditions. Both the spores and toxin will
survive normal cooking temperatures. Millions
required to cause illness. Bacteria multiply
between 3.3°C and 48°C.
Pathogenic Bacteria
Salmonella
Source
Raw meat
Poultry and eggs
Pests and pets
Human and animal intestines
Dirt and refuse
Symptoms
Vomiting
Nausea
Diarrhoea
Abdominal pain
Average Onset Time
12 - 36 hours
after eating
Staphylococcus
aureus
Human nose, throat, ears,
skin
Septic wounds
Animals and raw milk
Vomiting
Abdominal pain
Low temperature
1 – 7 hours after
eating
Clostridium
perfingens
Raw meat and poultry
Soil, dirt and refuse
Raw vegetables
Pests and pets
Human and animal intestines
Diarrhoea
Abdominal pain
12 - 18 hours
after eating
Clostridium
botulinum
Bacillus cereus
Soil
Marine sediment
Raw fish and meat
Animal intestines
Dust and soil
Cereal, rice and pasta
Paralysis
Breathing and
swallowing difficulty
Diarrhoea followed by
constipation
Nausea
Vomiting
Abdominal pain
Diarrhoea
12 – 36 hours
after eating
1 - 5 hours or 8 –
16 hours
depending on the
form of the food
poisoning
Campylobacter
enteritis
Escherichia Coli
0157
Listeriosis
That’s the end of lesson 1!
Coming next lesson: Foodborne diseases
Typhoid and paratyphoid
fever
Dysentery
Some People Face Special Risks
A variety of people may
face these special risks:
• Pregnant women
• Very young children
• People with chronic illnesses
or weakened immune systems
• Older adults
Why Older Adults?
Immune systems weaken
with age
Stomach acid decreases as
you get older
Diseases/illnesses may
further weaken the body
Recognizing Foodborne Illness
Can’t see, smell or taste bacteria in
food
Often takes 1 to 3 days to cause
illness, but can take up to 6 weeks
3 Pathogens of Special
Importance to Older Adults
Escherichia coli O157:H7
Salmonella
Listeria monocytogenes
E. coli
Lives in intestines of healthy cattle
and other ruminant animals.
Typical food sources:
• Undercooked ground meats,
• Contaminated produce served
raw (lettuce, spinach, sprouts),
• Unpasteurized milk
Salmonella
Salmonella outbreaks have been
associated with:
•
•
•
•
Raw and undercooked eggs
Undercooked poultry and meat
Raw milk
Produce and unpasteurized juice
 Why eggs?
• Salmonella can grow both inside the
egg and on the outside of shells
Listeria
Bacteria widespread in nature, soil,
water
Survives and grows at refrigerator
temperatures!
Risky Foods: Refrigerated Ready-to-Eat
foods (i.e. deli salads, lunch meats, hot
dogs, soft cheeses made with raw milk)
Listeria
Almost all cases: elderly, pregnant
women and immune-compromised
persons
Mild gastrointestinal symptoms: 8-48
hrs
Invasive illness: 2-6 weeks following
exposure
• Fever, muscle aches, headache, loss of
balance, bacteremia, meningitis,
encephalitis
Moulds and Yeasts
• Moulds are a type of fungi that will grow on
most foods and at many temperatures. Some
are used in food production such as cheese
manufacture. Unwanted moulds usually spoil
the food but do not cause food poisoning.
• Yeasts are another type of fungi that will
grow in food. They are used in making food
such as bread and beer but also spoil many
foods including jam, fruit juice, yoghurts and
meats
Food Poisoning bacteria
•Usually need millions of bacteria to
cause illness.
•The multiplication of bacteria within
the food plays an important part in
the disease
Spore
A resting resistant phase of some
bacteria (including Clostridium
Perfingens and Botulinum and Bacillus
Cereus). The bacterium produces a
protective coat which helps it to survive
high temperatures (up to 120°C) and
lack of water. When favourable
conditions return, the spores split open
and release the bacteria which are then
able to grow and multiply
Bacterial cell
Spore forming inside cell
Spore Formation
This is what happens …………..
Cell
Spore forms
in cell
Cell
disintegrates
Spore is
released
Spore starts
to germinate
Spore
continues to
germinate
Now see as, in suitable conditions, the cell
begins to divide (binary fission)………………………….
From raw materials to consumer:
Chemical, microbiological and technological aspects
of food
• Most of the food is treated in some way
to improve its shelf life, texture,
palatability
• or appearance. It would be difficult to
change this situation. So, it is important
to know
• what happens to the various food
components on the way from raw
material to consumer.
raw materials
Nutrients
natural toxins
contaminants
processing
hazardous
reaction
products
contaminants
food quality and safety
reduction and
prevention of
health risks
additives
Figure : Food: from raw material to consumer
the four categories of food components
are discussed in the following order:
1. natural toxins (including microbial toxins)
2. antinutritives
3. contaminants,
4.food additives and the rationale for their use
5. nutrients.
Natural Toxin
Endogenous toxins of plant origin
1 Toxic phenolic substances
Flavonoids
Tannins
Coumarin, safrole, and myristicin
2. Cyanogenic glycosides
Glucosinolate s
3 Natural contaminants
Mixing of edible plants with toxic plants
Contamination resulting from intake of toxic substances by animals
Contamination of milk with plant toxins
Natural toxins in aquatic organisms
4. Microbial toxins
Food-borne diseases
Bacterial toxins
Mycotoxins
Aflatoxins
Ochratoxin A
Antinutritives
3.1 Introduction
3.2 Type A antinutritives (antiproteins)
3.2.1 Protease inhibitors
3.3 Type B antinutritives (antiminerals)
3.3.1 Phytic acid
3.3.2 Oxalic acid
3.3.3 Glucosinolates
3.3.4 Dietary fiber
3.3.5 Gossypol
3.4 Type C antinutritives (antivitamins)
3.4.1 Ascorbic acid oxidase
3.4.2 Antithiamine factors
3.4.3 Antipyridoxine factors
Contaminants
4.1 Introduction
4.2 Contamination with heavy metals
4.2.1 Mercury
4.2.2 Lead
4.2.3 Cadmium
4.3 Nitrate
4.4 2,3,7,8-Tetrachlorodibenzo-pdioxin
4.5 Pesticide residues
4.6 Food contaminants from packaging
material
Food additives
5.1 Introduction
5.2 Use of food additives in relation to
their safety
5.2.1 Colorings
5.2.2 Flavoring agents
5.2.3 Preservatives
5.2.3.1 Antioxidants
5.2.3.2 Antimicrobials
5.2.3.3 Antibrowning agents
Nutrients
6.2 Macronutrients
6.2.1 Fats
6.2.1.1 Undesirable fat components in raw materials
6.2.1.2 Changes in dietary fats during storage and
processing of raw materials, and during
manufacturing, preparation and storage of food
6.2.1.2.1 Rancidity
6.2.1.2.2 Oxidation of fats and oils, and
adverse health consequences
6.2.1.2.3 Effects of processing techniques on the
oxidation of dietary fats and oils
6.2.2 Carbohydrates
6.2.2.1 Changes in dietary carbohydrates during manufacturing
and storage of food
6.2.3 Proteins
6.2.3.1 Changes in proteins during processing of raw materials,
and during manufacturing, preparation and storage of food
6.2.4 Pyrolysis products occurring in food
6.3 Micronutrients
6.3.1 Hypervitaminoses
6.3.1.1 Vitamin A
6.3.1.2 Vitamin D
What is Food Hygiene?
• The science of preserving health
• It involves all measures necessary to
ensure the safety and wholesomeness of
food during it’s preparation and storage
What does it involve?
• Rejecting contaminated food
• Decontaminating food
• Protecting food from contamination
through high standards of personal
hygiene, cleaning and disinfection
• Preventing any organisms multiplying
• Destroying any harmful bacteria by
thorough cooking
• Discarding unfit or contaminated food
Food Poisoning
• Normally associated with symptoms such as
diarrhoea and vomiting
• May also include headache, stomach cramps
and fever
• Bacteria are responsible for most cases
• Other causes include mycotoxins (poisonous
chemicals produced by some moulds)
Food Poisoning (contd.)
• Physical contamination:objects falling in to
food – metal, glass,
packaging materials etc.
• Chemical
contamination:- Bleach,
cleaning chemicals
getting in to food
• Natural contamination:
Poisonous plants and
berries, undercooked
red kidney beans
Poisonous mushrooms
The deathcap – one bite can prove fatal
And also…..The deadly Puffer fish!
Immunity to Microbes
The principal physiologic function of the
immune system is to protect the
host against pathogenic microbes such as
extracellular bacteria, intracellular
bacteria, virus or parasites. Important
features of immunity to microbes are
(a) defense is mediated by both innate and
adaptive immunity, (b) different
types of microbes stimulate distinct
population and subpopulations of
lymphocytes,
(c) survival of microbes or production of
disease depends on their
ability to evade immune system, and (d)
the tissue injury and disease consequent
to infection caused by host response rather
than the microbes itself.
Extracellular Bacteria
These organisms replicate outside the
cells, i.e., in circulation, interstitial
space, lumen of respiratory tract, and
intestinal tract. Examples of extracellular
bacteria include Clostridium,
Staphylococcus, Bacillus, Streptococcus,
Escherichia coli, and Vibrio species. They
cause disease either by inducing
inflammation or by direct action of toxins or
enzymes they produce.
Inflammation
Bacterial cells provoke inflammation that
result in tissue destruction and influx
of neutrophils and macrophages at the site
of infection. During inflammation,
complement activation takes place and
cytokines are released from macrophages.
Release of enzymes and toxins from
neutrophils and macrophages
causes cell injury and damage which is
also known as suppurative infection
(characterized by pus formation).
Sequence of events in inflammation
include
(1) increased blood supply to the site of
infection characterized by the development
of “redness,” (2) increased capillary
permeability and fluid accumulation
results in “swelling,” and (3) the recruitment
of neutrophils by chemotaxis
(C5a) and macrophages result in tissue
injury that invoke “pain.”
Toxins
Exotoxins cause diverse pathological
effects resulting in cell injury or cell death
(see Chap. 4 for details). For example,
Shiga and diphtheria toxins block protein
synthesis; botulinum toxin blocks
neurotransmitter release; and cholera toxin
stimulate cAMP synthesis resulting in Cl−
secretion and H2O loss. Endotoxin
(LPS and PGN) also called pyrogen,
stimulates the release of cytokines IL-1
and TNF-α; activate B-cells; and act as an
adjuvant to stimulate macrophage
to produce more cytokines. These
cytokines, induce fever, decrease smooth
muscle contraction, increase membrane
permeability, lower blood pressure,
and induce shock.
Innate Immunity
Innate immunity against extracellular
bacteria include (1) phagocytosis by
neutrophils, monocytes, and tissue
macrophages, (2) activation of complement
in the alternative pathway or mannose
lectin pathway by bacterial peptidoglycan
or mannose-binding lectin. The
complement activation byproduct C3b
enhances opsonization while MAC induces
cell lysis. (3) LPS activates macrophages
to produce cytokines TNF-α, IL-1, IL-6
which activate neutrophils
and macrophages to remove bacteria.
These cytokines also could induce fever
to retard bacterial growth or may induce
“septic shock” or “endotoxin shock”
leading to fatal consequences.
Antigen-mediated specific T-cell activation
results in specific cytokines
release which are responsible for isotype
switching to produce specific
antibodies.
2. Exotoxins are T-dependent antigens and
are processed by APC (macrophages,
B-cells) and presented via MHC class II
molecules to activate
CD4+ T-cells and B-cells for cytokine and
antibody production, respectively.
Certain toxins act as superantigens, which
induce T-cells to produce
increased cytokines leading to toxic shock
syndrome (TSS). For example,
staphylococcal enterotoxins (SEA, SEB,
SEC, SED, SEF, etc.) bind to
MHC class II on macrophages which
directly interacts with TCR of T-cells
and activate CD4+ T-cells to produce IFNγ, which in turn induce enhanced
MHC expression, antigen presentation,
and cytokine production in macrophages
leading to toxic shock syndrome.
3. Antibodies (IgG, IgM) help in the
influenzae, E. coli). Bacteria use surface
molecules for adhesion and colonization;
however, genetic variation in bacterial
surface molecules such as pili, fimbriae,
flagella or surface proteins will
evade antibodies antibodies developed
against previous form of molecules.
(2) Some bacteria (Bacillus anthracis, B.
cereus, and Pneumococcus spp.)
exhibit antiphagocytic mechanism. They
possess capsules, which are made of
sialic acid and hyaluronic acid (both are
also present in host cell membrane)
and prevent binding of C3b. As a result
these bacterial cells are not recognized
by macrophages for destruction. (3) Sialic
acid component of capsule also
inhibits complement activation. (4) Some
intracellular bacteria (Listeria
monocytogenes, Salmonella) are capable
of scavenging reactive oxygen using
superoxide dismutase (SOD) thus avert
toxic effects of oxygen radicals. (5) Some
bacteria (Staphylococcus aureus,
Streptococcus pyogenes) cover
Intracellular Bacteria
Several foodborne pathogens maintain
intracellular life cycle as part of their
infection strategy. After binding to specific
host cell receptor, they modulate
signaling events resulting in cytoskeletal
rearrangement and facilitating their
own entry. Bacteria trapped inside a
phagosome is either escaped by lysing the
vacuolar membrane or produce virulence
factors that sustain their intracellular
life style. Bacteria either spread from cellto-cell, or induce apoptosis, or cause
host cell lysis as part of their pathogenic
mechanism. The examples of intracellular
foodborne bacterial pathogens are Listeria
monocytogenes, Yersinia
enterocolitica, Shigella spp., and
Salmonella enterica.
Innate Immunity
Natural immunity including gastric acid, bile
salts, antimicrobial peptides,
mucins, and natural microflora provide
some protection; however, many
pathogens are resistant to those thus
natural immunity is less effective.
Furthermore, phagocytes (macrophages
and neutrophils) are also less effective
since bacteria are resistant to degradation
by lysosomal contents.