Microorganisms.

Processes that are involved to stop them spoiling food and advantages/disadvantages.

AS OCR F212 biology.

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MICROORGANISMS
PROCESSES THAT AFFECT MICROORGANISMS
When food is created using microorganisms, there needs to be controlled conditions otherwise food will be spoiled as
microorganisms will grow etc.
There are six types of treatment that you need to know about that affect microorganisms:
Freezing
Adding sugar
Adding salt
Pickling
Heat treatment
Irradiation
FREEZING
Some foods can be freeze dried, e.g. fruits, and this is done via putting the food into a vacuum, and this keeps food
below minus eighteen degrees Celsius.
The food doesn't freeze, the low pressure surrounding the food items turn into water vapour.
This does less damage as ice could pierce and break cell membranes.
Food keeps its texture better than conventional freezing.
SALTING AND ADDING SUGAR
Salting is traditionally used for meat, fish and some kinds of vegetables.
Salt may be rubbed into the food or the food is submerged into a low potential solution.
This interferes with the microorganism's ability to absorb water (which they need to survive).
This largely changes the flavour but many people like salted meats such as ham.
It is also used with sugar to prevent micro-organism s growing in jams or marmalades.
PICKLING
Enzymes and other proteins may denature if placed in an acidic solution.
Vinegar (an alkali) is often used for products such as pickles and they keep the food at its original condition.
HEAT TREATMENT
Microorganisms are killed by extreme heats; some heat-resistant pores can survive above 100 degrees.
The temperature in kitchen ovens can cause the microorganisms to die, this is due to the intense heat and this has
been adapted for the use in the food production industry.
Pasteurised milk is an example, it doesn't kill all of the bacteria (heats up to 65 degrees and then cools down to 20
degrees), and this is why milk can be stored for five days.
UHT (Ultra High Temperature) milk kills all bacteria as the milk is boiled and stored in a container.
IRRADIATION
Gamma radiation is often used.
Radiation can cause a change in chemicals in some food but there is no proof that it affects health.
PRODUCTION OF FOOD

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BREAD
It is made by mixing yeast, sugar, flour and water into a dough. The yeast turns the sugar into ethanol and carbon dioxide.
WINE
This is made by adding yeast to grape juice. The yeast turns the sugar in the grape juice into ethanol and carbon dioxide.
YOGHURT
This is made by adding bacteria to milk. The bacterium turns the sugar in the milk to lactic acid causing the milk to clot and
thicken into yoghurt.…read more

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