Bacteria & fungi feed by secreting enzymes on the food. These break down substances in the food. The microbes absorb the smaller molecules for growth. The food'll be changed to a mushy consistency. This changes the appearance, taste and smell.
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Why can a person become ill after eating gone off food?
Some micro-organisms produce toxic waste products which can make a person ill if they eat it.
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What are the two ways to prevent spoilage?
Killing any microbes already present. Preventing microbes from reproducing.
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How does drying protect food?
There's no moisture for microbes to grow.
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How does smoking prevent food spoilage?
It gives the food a protective coating.
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How should food packaging be designed?
To exclude air and microbes.
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Give 2 examples of using micro-organisms for food production.
Yoghurt- Milk with lactobacillus bacteria added. These use the sugar in milk to make lactic acid which thickens it into yoghurt. Bread- yeast respires the sugars present to release carbon dioxide which causes the bread to rise.
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Give another example of using micro-organisms for food production.
Cheese- solids from milk (curds) acted on by lactobacillus bacteria to change the texture. Fungi such as penicillium can be added to create blue cheese.
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What are mycoproteins?
A protein food source made by fungi. The most commonly used is the Fusarium fungus which makes Quorn. They are high in protein and contain no animal fat or cholesterol.
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How is mycoprotein produced?
In a fermenter. Fungus is circulated inside. When ready to harvest, heated to kill fungus, then fungal cells extracted and prepared for human consumption.
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Why does the fermenter culture medium contain glucose syrup?
Provides the growing fungus with a substrate to respire, so it can release energy for growth. Glucose is a source of carbon, to make organic molecules.
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Why is ammonia added with air to the fermenter?
It is a source of nitrogen, needed by the fungus to make amino acids and proteins needed for growth. Also needed to make new DNA for cell growth.
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Why are small amounts of trace minerals added to the fermenter?
Many enzymes need trace mineral elements to act as co-factors in order to function. Helps fungal enzymes to work at optimal rates.
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Why does the growth medium containing the fungus have to circulate over an area of cooling water?
There are many reactions going on inside the fermenter as the yeast respires and grows. These generate heat which could kill the fungus if the temperature gets too high (as the enzymes denature). This cools everything down.
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why are gases constantly removed from the fermenter?
Gases are produced by fungal respiration as well as the ammonia and air added, so some need to be removed regularly to avoid pressure build-up.
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Why is no stirrer used in the fermenter?
The fungus is made of long, thread-like hyphae which are easily broken.
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What are the advantages of using microbes for human food?
Fast protein production. Production can easily be tailored to meet demands. No animal welfare issues. Alternative protein source for vegetarians. No saturated fat. Low cost to make.
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What are the disadvantages of using microbes for human food?
Many people don't like the idea of eating fungi grown on waste products. Doesn't have the same taste or texture as meat. Risk of contamination in fermenter.
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Other cards in this set
Card 2
Front
Why can a person become ill after eating gone off food?
Back
Some micro-organisms produce toxic waste products which can make a person ill if they eat it.
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