25th July 2020




DATE: 4th July, 2020

CLASS: Grade 4

SUBJECT: Pre-vocational Studies

TOPIC: Risk Factors in Raw Food Items, Contamination and Reasons/Methods of Cooking Food.

REFERENCE: Lantern Comprehensive Pre-Vocational Studies Book 5.


Risks is anything that can cause us harm or danger.

Notes for the Pupils

Risk Factors in Raw Food Items and Contamination

Risk is anything that can cause us harm or danger. The factors that can increase the risk of food contamination are classified as biological, chemical and physical factors.

  1. Biological Factors: These are organisms or substances produced by organisms that live in food and can cause harm to humans when the food is eaten. Harmful organisms include bacteria, fungi and viruses. A fungus called mould causes food decay.
  2. Chemical factors:

(a) Toxins: some raw food contain naturally occurring chemical toxins such as hydrocyanic acid in cassava and ricin in legumes. These can cause serious harm if not removed during food processing.

(b) Pesticide and Herbicide: Some chemicals are introduced into our food from the farm through the wrong use of pesticides and herbicides.

(c) Additives: Some food additives used during food preparation or processing can also cause harm. An example is potassium bromate which was used in the past for making bread.

  1. Physical Factors:

(a) Contaminants: when crops are harvested from the farm, thy are usually stored alongside with straw, sand, stone and adhering plant matter. These materials can mix up with crops, especially grains and contaminate them.

(b) Pests: Rats and cockroaches can contaminate raw food if not properly stored. They introduce their faeces, eggs and hair which may accidentally be consumed along with food.

Meaning and Reasons for Cooking Food

Cooking is the application of dry or moist heat to raw foods to help break down completely chemical components and make them suitable for consumption.

Reasons for Cooking Food

  1. Health: Proper cooking helps to kill micro-organisms in food that can cause harm to humans. Heating of food beyond boiling point kills most bacteria.
  2. Digestion: Cooking helps to break down complex chemicals in food, this helps the food to digest easily.
  3. Flavour: it adds variety and flavour to food. For example cowpea (beans) can be boiled, made into bean cakes locally called “akara” or made into bean pudding, locally called moi-moi. Each of these three foods has a different taste.
  4. Beautification: Cooking improves the appearance of food. For example both akara and moi-moi look very different from beans after cooking. Fufu does not look anything like cassava after preparation, pounded yam looks very different from yam after preparation and cakes look very different from your flour after baking.
  5. Preservation: Cooking preserves food and helps to prevent it from becoming rotten. For example, cooked meat last longer than raw meat.


  1. What is cooking?
  2. State five reasons for cooking food.
  3. State 3 factors that can cause contamination risk in raw food.
  4. How does each of the factors mentioned in question 3 cause contamination?