(a) Complete the table below; Disease Causative organism Vector Control Cholera Trypanosome Female Anopheles mosquito Ringworm None (b) Explain briefly the ...

Answer Details

(a) Completed table

(b) Biological basis of food preservation

(i) Salting

Adding salt creates a very concentrated (hypertonic) medium around the food. Water is drawn out of the micro-organisms by osmosis, dehydrating them so they cannot grow, multiply or spoil the food. The dry, salty condition also removes the water that microbes need.

(ii) Irradiation

Food is exposed to ionising radiation (such as gamma rays). The radiation destroys or damages the cells and DNA of bacteria, fungi and other micro-organisms (and inactivates enzymes), killing them so they can no longer cause spoilage.

(iii) Smoking

Smoking dries the food by heat, removing water that micro-organisms need. In addition, the smoke deposits antimicrobial chemicals (such as phenols and creosote) on the food surface which inhibit the growth of bacteria and fungi.