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Flashcards in M22. Food Deck (31)
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What are the 4 main ways that/micro organisms can spoil our food

-visual growth of microorganisms on food, eg fungi
- micro organisms use an external digestion process
- The bacterium Clostridium botulinum produces a toxin called botulin
- The presence of the microorganismsin food can cause infection


give an example of visual growth of microorganisms on our food?

This is most obvious when fungi grow on food. For example, colonies of moulds Mucor and Penicilium often grow on bread. This mould has usually been growing for a few days before it becomes noticeable as either black (Mucor) or blue/green (Penicillium) mould.


How do microorganisms use external digestion processes to spoil food??
What effect does this have on the food?

They release enzymes into the food and absorb the nutrients released by breaking down the food molecules.
When this happens food usually smells sweet as sugar is released from carbohydrate molecules and the food will eventually be reduced to a mush by the action of the enzymes


What is the effect when The bacterium Clostridium botulinum produces a toxin called botulin?

It causes botulism. If these bacteria are growing on food, the toxin will be present, that is one of the most toxic known toxins- just 1ug can kill a person


Give an example of how The presence of the microorganismsin food can cause infection can cause food spoilage

Eg the Salmonella bacteria, sometimes present in poultry products, attack the lining of the stomach and digestive system.


Name 8 methods of preventing food spoilage

-Eating food quickly while its fresh
- cooking
- drying/ salting/ covering in sugar


How does cooking prevent food spoilage?

the heat denatures enzymes or other proteins and kills the micro organisms


How does pasteurising prevent food spoilage?

by heating to 72 degrees for 15 seconds then cooling rapidly to 4 degrees kills any harmful micro organisms.


How does drying/salting/covering food in sugar prevent food spoilage?

As this dehydrates microorganisms as water leaves them via osmosis


How does smoking prevent food spoilage?

As the food developed a hard, dry outer surface and the smoke contains antibacterial chemicals.


How does pickling prevent food spoilage?

as it uses acid pH to kill micro organisms by denaturing their enzymes and other proteins.


How does irradiation prevent food spoilage?

as the ionising radiation kills the micro organisms by disrupting their DNA structure


How does cooling or freezing prevent food spoilage

As although this does not kill micro organisms, but it retards enzyme activity so their metabolism, growth rate and reproduction is very very slow.


How can canning prevent contamination?

As the food is heated and then placed in an airtight container


How can contamination be prevented further?

-vacuum wrapping
- plastic/paper packaging.


How can vacuum wrapping products prevent further contamination/

air is excluded so microbes cant respire aerobically.


Give 4 examples of how micro organisms are used to make food

- Yoghurt is milk that has been affected by Lactobacillus bacteria
- Cheese has made from curdled milk
- Bread is risen by yeast
- Alcohol is produced when yeast respires anaerobically.


How is yoghurt made?

The lactobacillus bacteria uses the lactose sugar in milk to make lactric acid, which causes the milk protein to thicken. The bacteria partially digests the milk, making it easily digestible for humans


Why is yoghurt beneficial?

As it helps to ensure that our digestive system contains the non-pathogenic bacteria it needs to aid digestion


How is cheese made?

The solid part of the milk (curds) is acted upon by Lactobacillus bacteria, and these cheese is given extra flavour by contamination with fungi such as Penicillium to produce blue cheese.


What causes bread to rise?

As yeast respired anaerobically, carbon dioxide is produce, causing bubbles of gas which causes the dough to rise.


How is alcohol produced?

Due to the anaerobic respiration of yeast.
Grapes contain the


How is beer made?

Cereal grains containing the sugar maltose can be used to brew beer, as the yeast respires the sugar.


How is wine made?

Grapes contain the sugars fructose and glucose, which the yeast uses in making wine.


Give an example of microorganisms that have been used to produce a protein?

The single celled protein (SCP), the best known type is Quorn, a mycoprotein- a protein made by fungus


Why is Quorn thought to be a healthier option to meat?

As it contains no animal fat or cholesterol.


Why is there such a great potential in SCP production using micro organisms such as Kluyveromyces, Scytalidium and Candida.

As they can produce protein with similar amino acid profiles to animal and plant protein
And they can grow on almost any organic substrate including waste materials such as paper and whey.


Name 6 advantages of using micro organisms to produce SCP

- Production of protein can be many times faster than that of an animal or plant protein.
-Production can be increase and decreased easily according to demand.
- There are no animal welfare issues
- Good source of protein for vegetarians
- Contains no animal fat or cholesterol
- SCP production could be combined with the removal of waste products like whey


Name 5 disadvantages of using micro organisms to produce SCP

- many people may not want to eat fungal protein/food that has been grown on waste
- isolation of the protein, the micro organisms are grown in huge fermenters and need to be isolated from the material on which they grow
- the protein has to be purified to ensure it hasnt been contaminated
-infection is a risk due to ideal conditions
- Palatability, (the protein does not have the same taste or texture of traditional protein sources.


Why is infection a high risk in the production of SCP?

the conditions needed for the useful microorganisms to grow are also ideal for pathogenic organisms so care must be taken to ensure the culture is not infected with the wrong organisms`