Food and Nutrition Nov/Dec.2011  
Questions: 1 2 3 4 5 6 Main
General Comments

Question 4

(a)      (i)      Explain two methods of preserving food.
(ii)      Give an example of the food that can be preserved using each of the methods.

(b)     Explain one effect of heat on raw egg.

  1. (i)      State two reasons for rechauffe´ cookery.
  2. (ii)      Mention two rechauffe´ dishes.




This question was the candidates’ strength, because all the candidates attempted the question and they all got it right.

The answers to the question are as follows:


(i)      DRYING/DEHYDRATION: is the process of removing the moisture content (water) of the food to create an unfavourable environment/condition for the action of food enzymes and micro-organism to prevent spoilage
e. g. fish, meat, cereals, legumes, tubers, fruits, vegetables, milk etc.
(ii)      LOW TEMPERATURE TREATMENT/FREEZING:- is a process of keeping the food at a low temperature by freezing below 0oc in the freezer e.g. fish, meat.
(iii)     HIGH TEMPERATURE TREATMENT/APPLICATION OF HEAT: is a process of destroying food enzymes and micro-organisms by heating. It can be by pasteurization or sterilization e.g. milk, tomato puree, canned meat and fish.
(iv)     USE OF CHEMICALS:- is the addition of chemicals such as sugar and salt to food to inhibit/stop the action of food enzymes. They create an unfavourable environment/ prevent chemical reactions from taking

place in the food.  They hold up the moisture present in the food in suspension e.g. cheese, meat, fish, pickles, jam, jelly, marmalade.
(v)      CANNING AND BOTTLING:- is a process of keeping food in cans or bottles/keeping food free from bacteria. The food is sterilized, sealed in vacuum or in the presence of inert gases to prevent oxidation e.g. fruit juices, meat, fish, fruit purees, beverages, jam, jelly, marmalade.
(vi)     IRRADIATION:- is the use of radioactive elements like cobalt to destroy micro-organisms and enzymes in foods e.g. potato, yam tubers fruits, vegetables, pulses, cereals, pork and shell fish. 
(vii)    FERMENTATION:- it involves the decomposition of some of the food components to produce acids making the food unfavourable to microorganisms e.g. locust bean seeds (iru/dawadawa/kanda ogiri) and wines.
(viii)   Removal/EXCLUSION OF AIR:- Foods are temporarily preserved by vacuum packaging and modified atmosphere packaging. They are wrapped in an impermeable plastic film e.g. cold meat, cheese, sausages, yoghurt and fish.
(ix)     SMOKING:- The food is exposed to smoke from burning wood and the chemical in the smoke kills any micro-organisms on the food and helps to prevent further  attacks on the food. The heat also reduces the moisture content in the food e.g. fish, meat and snails.

          (i)      Cooking coagulates the protein in the egg leading to egg shrinkage
          (ii)      Further cooking hardens and denatures the protein
(iii)     There is colour change. The albumen changes from opaque to       white and the yolk from gold to yellow.
                    -        to prevent wastage/spoilage
                   -        to cut down on cost
                   -        to provide variety in the family menu
                   -        to make the food more appetizing
                   -        to make the food more easily digestible
                   -        to develop new dishes

Kedgeree, rice/yam balls, rice pudding, shepherd/fish/meat pies, yam pottage/ebeh, meat/chicken/potato rollovers, potato cake, potato salad, fish rolls, fish cakes, fish cutlets, meat croquettes, rissoles, meat loaf, meat pepper soup, chicken soup, trifle, cheese cake, chocolate flan, duchess yam/potato, pie, mpotompoto, fritters.

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