Microorganisms and Food

Biology

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  • Created by: alex
  • Created on: 24-05-11 13:30

Microorganisms and Food

Bread - the yeast turns to carbon dioxide and ethanol. The CO2 makes the bread rise.

Wine - yeast turns the sugar in the grape to ethanol (alcohol) and C02.

Cheese - bacteria turns the sugar in the milk to lactic acid which causes the milk to curdle.

Microorganisms:

  • grow rapidly under the right conditions - quick food production
  • grow on a range of inexpensive materials
  • environment can be artificially controlled - can be grown anywhere
  • conditions for growth are easy to create
  • can last longer in storage than the raw product they're made from.

but..

  • there's a high risk of food contamination as conditions are favourable to harmful microorganisms
  • small changes in temperature or pH coulf kill the microorganisms
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Prevention of Spoilage

Salting

  • Salt inhibits the growth
  • interferes with the ability to absorb water
  • water moves down concentration gradient into the salt

Adding Sugar

  • same as salting

Freezing

  • slows down the reactions taking place in microorganisms
  • freezes the water in the food so microorganisms can't use it

Pickling

  • vinegar has a low pH which reduces enzyme activity
  • this inhibits their growth

 

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.

Heat Treatment

  • kills any microorganisms present

.

Irradiation

  • involves exposing foods to radiation
  • X-rays or Gamma Rays
  • kills any microorganisms present.
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