Transcript Microorganisms In Making Food

OCR AS Biology – F212 – Module 2
Food & Health
(e) explain that humans depend on plants for
food as they are the basis of all food chains.
(No details of food chains are required)

Humans are dependent on plants as
they are the basis for all food chains
(f) outline how selective breeding is used to produce
crop plants with high yields, disease resistance and
pest resistance
(g) outline how selective breeding is used to produce
domestic animals with high productivity
Chose organisms with characteristic you
want, breed together individuals with that
characteristics, repeat
 E.g. Crops with high yield, disease
resistance and pest resistance
 E.g. domestic animals with high productivity

(h) describe how the use of fertilisers and
pesticides with plants and the use of antibiotics
with animals can increase food production

Use of fertilisers and pesticides (plants)
 Fertilisers: provide minerals for growth
 Pesticides: kill pests that feed on crop,
reducing amount of plants damaged/destroyed

Use of antibiotics (animals)
 Don’t waste energy fighting disease
 Promote growth by affecting bacteria in gut
 Increase the size of animals when mature
Questions
1)
2)
3)
Explain how food production can be
increased with the use of pesticides
Briefly describe how selective breeding
is used to increase food production
Give 2 advantages of using selective
breeding
Answers
Explain how food production can be increased with the use of
pesticides
1)
•
•
•
Kills pests
Less plants destroyed
Increased yield
Briefly describe how selective breeding is used to increase food
production
2)
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•
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•
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Select organisms with useful characteristics to increase food production
Breed together
Select offspring with best characteristics
Breed together
Repeat
Give 2 advantages of using selective breeding
3)
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•
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Produce high yielding animals/plants
Produce organisms with increased resistance to disease so need to use
less pesticides/antibiotics
Increased tolerance to poor conditions
Learning Objectives
Success Criteria
Understand that food
spoilage can be harmful
to human health.
 Understand the methods
used to prevent food
spoilage.
 Understand how
microorganisms can be
used to make food.
 Discuss the advantages
and disadvantages of
using microorganisms.


Recall the ways in which
food spoilage can be
seen (E-D)
 Describe the ways in
which food spoilage can
be prevented (C-B).
 Explain how
microorganisms can be
used to make food and
the
advantages/disadvantag
es of this (A-A*)
Starter

If a nuclear holocaust was imminent, what kind
of food would you stock in your bomb shelter to
last you through the next few months?
Canned Food
Dry Cereals
Dried/
Salted
Snacks
Pickled Food
Smoked
Food
Food Spoilage

How do we know food is spoilt?
The signs of food
spoilage are not
always immediately
visible.
For example, meat left out for a while may be
covered in harmful bacteria.
 The meat may look fine to eat, but consumption
could cause major illness.

Food Spoilage – Visible Growth

Moulds are the most obvious visible form of
microorganism on our food.
An orange
covered in
Penicillium
fungus
Mucor fungus on bread.
Fungi like the ones above feed saprophytically.
 This means they secrete enzymes onto food and
then absorb the products into their cells.

Food Spoilage – Toxins
Some microorganisms release toxins onto our food.
 This can cause serious illness, especially in the case of
Clostridium botulinium.
 This bacteria releases botulin, of which as little as 1µg can
kill a person.

C. botulinium causes the
disease, botulism.
Food Spoilage – Infection



A very common problem caused by eating spoilt food is
infection.
Salmonella bacteria is associated with poultry (both meat &
eggs).
The bacteria attack the lining of the stomach and intestine.
Preventing Food Spoilage

Use the bottom half of page 158 to find out how fresh food
can be saved from spoilage.
Method
Salting
Adding sugar
Pickling
Cooling/Freezing
Heat Treatment
Irradiation
Drying
How it works...
(j) outline how salting, adding sugar, pickling,
freezing, heat treatment and irradiation can be used
to prevent food spoilage by microorganisms

Bacteria break down food by releasing
enzymes and breaking down molecules into
their component parts

Drying/Salting – dehydrate microorganisms
Adding Sugar – dehydrate microorganisms
Pickling – pH kills microorganisms
Freezing – slow growth
Heat Treatment – denatures enzymes
Irradiation – disrupts DNA

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
Microorganisms in Making Food

Microorganisms aren’t all bad – they can be used to make food too.
Yoghurt
Lactobacillus uses lactose in milk to
make lactic acid. The milk is partially
digested by the bacteria.
This makes it easy to digest for us.
Cheese
Milk is allowed to curdle. The solid,
curdled milk is acted upon by
Lactobacillus and additional flavours
can be achieved by contamination
with Penicillium.
(e.g. Blue cheese)
Microorganisms in Making Food
Bread
Bread is made to rise by yeast.
Yeast respires anaerobically,
releasing carbon dioxide bubbles.
These cause bread to rise.
Alcohol
Cereal grains contain the sugar
maltose, which yeast respire upon.
Alcohol is produced as a product of
anaerobic respiration by the yeast.
Cereals are replaced with grapes
when making wine.
QuornTM


A very well-known protein produced by a fungus is Mycoprotein.
This is the protein present in the meat-substitute food product known
as Quorn.
The mycoprotein in
Quorn is made by
the fungus:
Fusarium venenatum

Quorn is a very healthy option as it contains no animal fat or
cholesterol, which as you now know can be harmful to health.
Question
1)
2)
3)
4)
Describe an example of the use of
microorganisms in food production
What is meant by the term ‘food
spoilage’
Describe how adding sugar to food can
prevent spoilage
What is the name of the food
preservation that involves exposing
food to gamma or x rays?
Answers
1)
•
•
•
•
2)
•
3)
•
•
4)
•
Describe an example of the use of
microorganisms in food production
Bread making (yeast makes carbon dioxide)
Wine making (yeast turns sugar into alcohol)
Cheese making (bacteria curdles milk)
Yoghurt (bacteria turn sugar into lactic acid)
What is meant by the term ‘food spoilage’
Deterioration of the food’s characteristic
Describe how adding sugar to food can
prevent spoilage
Inhibits growth of microorganisms
By interfering with their water absorption
What is the name of the food
preservation that involves exposing food
to gamma or x rays?
Irradiation
Think, Pair, Share
(i) describe the advantages and disadvantages of
using microorganisms to make food for human
consumption

Advantages





Faster production of protein
Increased/decreased on demand
No animal welfare issues
Source of protein for vegetarians
Disadvantages
 Not want to eat food grown on waste
 Protein needs to be isolated
 Could grow pathogenic organisms by
accident
 Not taste or texture of traditional protein
Learning Objectives
Success Criteria
Understand that food
spoilage can be harmful
to human health.
 Understand the methods
used to prevent food
spoilage.
 Understand how
microorganisms can be
used to make food.
 Discuss the advantages
and disadvantages of
using microorganisms.


Recall the ways in which
food spoilage can be
seen (E-D)
 Describe the ways in
which food spoilage can
be prevented (C-B).
 Explain how
microorganisms can be
used to make food and
the
advantages/disadvantag
es of this (A-A*)
Plenary
[3]
bacteria / (bacterial) cells, divide / increase in number /
multiply / reproduce / proliferate / replicate ;
 (secrete) enzymes / named enzyme ;
 food, digested / broken down ;
 protein / named protein / polypeptides → peptides /
amino acids





OR
fat / triglycerides → fatty acids
OR
starch / amylose / glycogen → glucose / sugar ;
production / release / excretion / secretion, of, toxins /
named toxin / waste products ;
 (causes) change in, appearance / smell / texture / taste
;

[3]







bacteria, reproduce / AW, more rapidly / faster ;
(so) more bacteria present ;
more, toxins / waste, produced / released / AW
more enzymes, secreted / AW ;
enzyme, action faster / works better / more effective,
at higher temperatures ;
(substrate and enzymes have) more kinetic energy ;
more, enzyme-substrate complexes / ESC /
(successful) collisions between substrate and active
site ;
[4]

salting ;
 lack of water due to, osmosis / low water potential (outside cell) ;

sugar ;
 lack of water due to, osmosis / low water potential (outside cell) ;

(air / freeze) drying ;
 idea that enzymes cannot mobilise / intracellular transport impaired / reactions
have no medium in which to occur /
 (microbes) cannot move ;

pickling / (use of) vinegar ;
 (low pH) denatures / changes tertiary structure of / changes 3D shape of,
enzymes / proteins
 substrate no longer fits active site / active site shape changes / prevents ESC ;

heat treatment / cooking ;
 denatures / changes tertiary structure of / changes 3D shape of, enzymes /
proteins
 substrate no longer fits active site / active site shape changes / prevents ESC ;

irradiation / UV / gamma rays / X-rays / ionising radiation ;
 destroys / damages / changes / mutates, DNA / genes / genetic material ;