Food Poisoning,Nitrogen Cycle and More : Science For Class 8th

  • Food if not stored properly ,get spoiled due to the action of enzymes present in it or due to the gowth of bacteria.

How is spoilt food affected

  • Emits Bad smell or foul smell
  • Taste is changed
  • Nutitional value is affected
  • Colour changes

What are the causes of food Poisoning?

  • Food Poisoning is caused by  mIcroorganisms such as bacteria and fungipresent in  the spoiled food

The common bacteria causing food poisoning are

  • Salmonella
  • Staphylococci
  • Clostridium Botulinum
  • Aspergillus

The Toxins produced in the food by bacteria and fungi

The traces of pesticide

The metal salts produced by the action of food with the material of the container or cooking utensils

Why Food Preservation and how it is done?

  • The  process by which spoilage of perishable foods is prevented using chemicals or physical method is called food preservation

The Most Common methods used are

  1. By Sun Drying- Drying in the sun reduces the moisture content of food material
    Removal of water from food materials like vegetables(suh as Cauliflower spinach fruits ) are called dehydration
    Micro organisms cannnt grow in dry condition

2. By Heating – Heating kill germs. milk at home is prevented from spoilage by boiling

3. By salting sugar – fruits and vgetables are commonly preserved by using salt or sugar.
Food items are madeinto Jams and Jellies and Pickles. In Jams sugar is used and in pickles salt is used.
Sugar and salt remove from water from the cells there by preventing growth of microorganisms

4. By oil Vinegar and spices-

5. By Refrigeration and Freezing- Low Temperature Prevents growth of microorganisms

Refrigeration below5 degree keepsw food fresh for few days

A freezer which provides temperature below -18degree can store food for many months

Frozen foods should be throughly cooked and should not be left opened for too long. otherwise the microbes become active again

By Pasterisation

in this method milk is heated at about 60-65 degree for about 30 minutes to kill the bactgeria present in it. then cooling it quickly to prevent the growth of remaining bacteria.

Then milk is stored in sterilized packets.

Find Who DEveloped Paserisation method?

By proper storage and packing


Nitogen Fixation/Nitrogen cycle

The process of conversion of free atmospheric nitrogen into useful nitogen compounds is called fixation of nitrogen .

There are two ways by which atmospheric ntrogen is fixed

Natural fixation of nitrogen

Artificial fixation of nitrogen

Natural fixation of nitrogen

By SYmbiotic bacteria –

Image result for nitrogen fixation


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