food contamination and spoilage
DESCRIPTION
food contamination and spoilageTRANSCRIPT
Food contamination and spoilage
Presented by :-
Learning objectives
• To know the three methods of food contamination.
• To understand the two dierent food changes through autolysis and micro-organisms.
• To identify ositi!e food changes.
• To know the conditions which romote "acterial growth.
3
What is food spoilage?
• Food Spoilage is the rocess in which food reaches to the oint in which it is not edi"le to humans or its $uality of edi"ility "ecomes reduced. %arious e&ternal forces are resonsi"le for the soilage of food.
4
Factors :-
• 'ar!ested foods decomose from the moment they are har!ested due to attacks from en(ymes) o&idation andmicroorganisms. These include "acteria) mold) yeas t) moisture) temerature and chemical reaction.
5
6
Food contamination
• +hysical,
• hemical,
• acterial.
7
Physical contamination
This can occur in a !ariety of ways at dierent stages of food rocessing and roduction. /ome e&amles are*
• soil from the ground when har!esting,
• a "olt from a rocessing lant when ackaging,
• a hair from a cook in the kitchen.
are must "e taken at each stage to re!ent hysical contamination.
8
Chemical contamination
This can occur in a !ariety of ways at dierent stages of food rocessing and roduction. /ome e&amles are*
• chemicals from the farm,
• a cleaning roduct used in the rocessing lant when ackaging,
• y sray used in the kitchen when rearing food.
are must "e taken at each stage of food roduction to re!ent chemical contamination.
9
Bacterial contamination
1s soon as food is har!ested) slaughtered or manufactured into a roduct it starts to change. This is caused "y two main rocesses*
• autolysis – self destruction) caused "y en(ymes resent in the food,
• micro"ial soilage – caused "y the growth of "acteria) yeasts and moulds.
10
esirable food changes
1utolysis and micro "acterial changes are
sometimes desira"le and are not referred to as soilage3) for e&amle en(ymes cause fruit to rien.
'ere are some ositi!e micro "acterial
changes "elow.
5east in "read roduction. 11
!"tolysis - en#ymes
6n(ymes are chemicals that are found in food.
These chemicals ha!e imortant uses in food. They can cause food to deteriorate in three main ways*
• riening – this will continue until the food "ecomes inedi"le) e.g. "anana riening,
• "rowning – en(ymes can react with air causing the skin of certain foods) e.g. otatoes and ales discolouring,
• o&idation – loss of certain nutrients) such as !itamins 1) and thiamin from food) e.g. o!er "oiling of green !egeta"les.
12
$icrobial spoilage - bacteria
These are single celled micro-organisms they cannot "e seen "y the naked eye3 which are resent naturally in the en!ironment.
There are many dierent kinds) some are useful) e.g. in the roduction of yogurt) and some harmful.
The resence of "acteria in food can lead to digesti!e uset.
/ome "acteria roduce to&ins which can lead to this also.
/ores can also "e roduced "y some "acteria leading to to&ins "eing roduced.
13
$icrobial spoilage - yeast
5easts are single celled fungi which can reroduce "y 7"udding8. This means that a small oshoot or "ud searates from the arent yeast cell. 5easts can also form sores which can tra!el through the air. These are easily killed "y heating to 00:.
;n warm) moist conditions in the resence of sugar) yeasts will cause foods like fruit to ferment roducing alcohol and car"on dio&ide gas.
5east is used in the roduction of "read and wine.
14
$icrobial spoilage - mo"ld
4oulds are fungi which grow as <laments in food. They reroduce "y roducing sores in fruiting "odies which can "e seen on the surface of foods.
These fruiting "odies sometimes look like round furry "lue-coloured growths) e.g. mould on "read.
/ome moulds can "e seen "y the naked eye) e.g. on "read.
15
© Food – a fact of life
Conditions for bacterial gro%th
4icro-organisms need conditions to sur!i!e and reroduce these can include*
• temerature,
Temerature
The ideal temerature for "acterial growth is
=0: – =>:.
/ome "acteria can still grow at 0: and ?0:. 4ost "acteria are destroyed at temeratures a"o!e ?= :. acterial growth danger (one in @: - ?=:.
1t !ery cold temeratures) "acteria "ecome dormant – they do not die) "ut they cannot grow or multily.
17
00: Aater "oils
@: - ?=: danger (one for
-B: temerature of free(er 18
© Food – a fact of life
Conditions for bacterial gro%th
D&ygen /ome "acteria need o&ygen to grow and multily. These are called aero"ic "acteria. Dther "acteria grow well when there is no o&ygen resent) these are known as anaero"ic "acteria.
' le!el 1n acidic or alkaline en!ironment can romote of inhi"it micro"ial growth. 4ost "acteria refer a neutral ' ?.? – >.@3. 4oulds and yeasts can sur!i!e at ' le!els of -E@ !ery acidic3) food soilage usually occurs "y yeast and moulds.
19
© Food – a fact of life
Conditions for bacterial gro%th
4oisture Ahere there is no moisture "acteria cannot grow. 'owe!er) "acteria and moulds can "oth roduce sores which can sur!i!e until water is added to the food.
Food acteria need a source of food to grow and multile) these food usually contain large amounts of water and nutrients.
Time
Common Foodborne &llnesses ca"sed by food spoilage:-
&llness
•a% prod"ce
•a% mil+
•Soft cheese
&nfections and its Symptoms .o% does foodborne illness occ"r?
– Contaminated foods carry microbes into the body
– Some microbes can overcome the body/s defenses
and ca"se infections
– 0a"sea
– 1omiting
© Food – a fact of life
is+s 2o" Can Control :- •;mroer refrigeration and storage
•+oor ersonal hygiene
23
24
Good food safety*
• +re!ent contaminating food with athogens sreading from eole) ets) and ests.
• /earate raw and cooked foods to re!ent contaminating the cooked foods.
• ook foods for the aroriate length of time and at the aroriate temerature to kill athogens.
• /tore food at the roer temerature.
• Ho use safe water and cooked materials.
25
Good food hygiene rocedures *- • Aash hands often
• Iee raw meats and ready to eat foods searate
• ook food to roer temeratures
• Jefrigerate food romtly to "elow C0 degree F.
26
27
T'1KI 5D
Presented by :-
Learning objectives
• To know the three methods of food contamination.
• To understand the two dierent food changes through autolysis and micro-organisms.
• To identify ositi!e food changes.
• To know the conditions which romote "acterial growth.
3
What is food spoilage?
• Food Spoilage is the rocess in which food reaches to the oint in which it is not edi"le to humans or its $uality of edi"ility "ecomes reduced. %arious e&ternal forces are resonsi"le for the soilage of food.
4
Factors :-
• 'ar!ested foods decomose from the moment they are har!ested due to attacks from en(ymes) o&idation andmicroorganisms. These include "acteria) mold) yeas t) moisture) temerature and chemical reaction.
5
6
Food contamination
• +hysical,
• hemical,
• acterial.
7
Physical contamination
This can occur in a !ariety of ways at dierent stages of food rocessing and roduction. /ome e&amles are*
• soil from the ground when har!esting,
• a "olt from a rocessing lant when ackaging,
• a hair from a cook in the kitchen.
are must "e taken at each stage to re!ent hysical contamination.
8
Chemical contamination
This can occur in a !ariety of ways at dierent stages of food rocessing and roduction. /ome e&amles are*
• chemicals from the farm,
• a cleaning roduct used in the rocessing lant when ackaging,
• y sray used in the kitchen when rearing food.
are must "e taken at each stage of food roduction to re!ent chemical contamination.
9
Bacterial contamination
1s soon as food is har!ested) slaughtered or manufactured into a roduct it starts to change. This is caused "y two main rocesses*
• autolysis – self destruction) caused "y en(ymes resent in the food,
• micro"ial soilage – caused "y the growth of "acteria) yeasts and moulds.
10
esirable food changes
1utolysis and micro "acterial changes are
sometimes desira"le and are not referred to as soilage3) for e&amle en(ymes cause fruit to rien.
'ere are some ositi!e micro "acterial
changes "elow.
5east in "read roduction. 11
!"tolysis - en#ymes
6n(ymes are chemicals that are found in food.
These chemicals ha!e imortant uses in food. They can cause food to deteriorate in three main ways*
• riening – this will continue until the food "ecomes inedi"le) e.g. "anana riening,
• "rowning – en(ymes can react with air causing the skin of certain foods) e.g. otatoes and ales discolouring,
• o&idation – loss of certain nutrients) such as !itamins 1) and thiamin from food) e.g. o!er "oiling of green !egeta"les.
12
$icrobial spoilage - bacteria
These are single celled micro-organisms they cannot "e seen "y the naked eye3 which are resent naturally in the en!ironment.
There are many dierent kinds) some are useful) e.g. in the roduction of yogurt) and some harmful.
The resence of "acteria in food can lead to digesti!e uset.
/ome "acteria roduce to&ins which can lead to this also.
/ores can also "e roduced "y some "acteria leading to to&ins "eing roduced.
13
$icrobial spoilage - yeast
5easts are single celled fungi which can reroduce "y 7"udding8. This means that a small oshoot or "ud searates from the arent yeast cell. 5easts can also form sores which can tra!el through the air. These are easily killed "y heating to 00:.
;n warm) moist conditions in the resence of sugar) yeasts will cause foods like fruit to ferment roducing alcohol and car"on dio&ide gas.
5east is used in the roduction of "read and wine.
14
$icrobial spoilage - mo"ld
4oulds are fungi which grow as <laments in food. They reroduce "y roducing sores in fruiting "odies which can "e seen on the surface of foods.
These fruiting "odies sometimes look like round furry "lue-coloured growths) e.g. mould on "read.
/ome moulds can "e seen "y the naked eye) e.g. on "read.
15
© Food – a fact of life
Conditions for bacterial gro%th
4icro-organisms need conditions to sur!i!e and reroduce these can include*
• temerature,
Temerature
The ideal temerature for "acterial growth is
=0: – =>:.
/ome "acteria can still grow at 0: and ?0:. 4ost "acteria are destroyed at temeratures a"o!e ?= :. acterial growth danger (one in @: - ?=:.
1t !ery cold temeratures) "acteria "ecome dormant – they do not die) "ut they cannot grow or multily.
17
00: Aater "oils
@: - ?=: danger (one for
-B: temerature of free(er 18
© Food – a fact of life
Conditions for bacterial gro%th
D&ygen /ome "acteria need o&ygen to grow and multily. These are called aero"ic "acteria. Dther "acteria grow well when there is no o&ygen resent) these are known as anaero"ic "acteria.
' le!el 1n acidic or alkaline en!ironment can romote of inhi"it micro"ial growth. 4ost "acteria refer a neutral ' ?.? – >.@3. 4oulds and yeasts can sur!i!e at ' le!els of -E@ !ery acidic3) food soilage usually occurs "y yeast and moulds.
19
© Food – a fact of life
Conditions for bacterial gro%th
4oisture Ahere there is no moisture "acteria cannot grow. 'owe!er) "acteria and moulds can "oth roduce sores which can sur!i!e until water is added to the food.
Food acteria need a source of food to grow and multile) these food usually contain large amounts of water and nutrients.
Time
Common Foodborne &llnesses ca"sed by food spoilage:-
&llness
•a% prod"ce
•a% mil+
•Soft cheese
&nfections and its Symptoms .o% does foodborne illness occ"r?
– Contaminated foods carry microbes into the body
– Some microbes can overcome the body/s defenses
and ca"se infections
– 0a"sea
– 1omiting
© Food – a fact of life
is+s 2o" Can Control :- •;mroer refrigeration and storage
•+oor ersonal hygiene
23
24
Good food safety*
• +re!ent contaminating food with athogens sreading from eole) ets) and ests.
• /earate raw and cooked foods to re!ent contaminating the cooked foods.
• ook foods for the aroriate length of time and at the aroriate temerature to kill athogens.
• /tore food at the roer temerature.
• Ho use safe water and cooked materials.
25
Good food hygiene rocedures *- • Aash hands often
• Iee raw meats and ready to eat foods searate
• ook food to roer temeratures
• Jefrigerate food romtly to "elow C0 degree F.
26
27
T'1KI 5D