Lesson Note

Subject: Food And Nutrition
Topic: Food Preservation
Lesson Objective: by the end of this lesson, the learners should be able to:

  1. Define the terms “Food Spoilage and food preservation”;
  2. Identify the causes of food spoilage;
  3. Categorize foods for preservation;
  4. Give reasons for preserving foods;
  5. Abide by the principles of food preservation;
  6. Suggest ways to make food preservation principles achievable;
  7. Preserve foods for future use.

Lesson Summary

We can’t talk about food preservation without first mentioning Food spoilage. Food spoilage gives rise to food preservation. How do I mean? The fear of having your food going spoiled is the reason behind food preservation. So what is Food Spoilage?

Food Spoilage

Food spoilage can be defined simply as unpleasant or undesirable changes that takes place in the food which eventually leads to its rejection and wastage.

Causes Of Food Spoilage

Food spoilage can be caused by the following factors
  1. Action of microorganisms such as bacteria yeast and moulds.
  2. Insects.
  3. Food enzymes.
  4. Chemical reactions in the food.
  5. Physical changes due to freezing, burning, drying, pressure, etc.

Categories Of Foods

For us to choose the right methods of food preservation, we should know the kind of food or category to which the foods belong. This will enable us sustain their durability. So let’s see the categories of different foods.
A. Perishable food or high moisture foods: these are food which begin to deteriorate almost immediately on left preserved in some ways because of their high water content. Examples of such foods are milk, meat, seafoods, many vegetables and fruits.
B. Semi perishable foods or intermediate moisture foods: these are food which can be kept for sometime before going bad. Their water content is low. Examples of such food are root vegetables and tubers.
C. Non-perishable foods or low moisture foods: these are foods which can be kept for a reasonably long time without getting spoiled due to their low water content. Examples of such foods are nut, dried legumes, and cereals.

Reasons for food preservation

  1. We preserve foods to avoid wastage especially when there is plenty of food.
  2. We preserve foods for use during off season of such foods.
  3. To eliminate the purchase of foods when they are most expensive.
  4. To have a variety of foods available for an emergency situation.

Principles Of Food Preservation

The act of food preservation is based on the following principles:
  • Destruction of microorganisms.
  • Prevention of their entry into the food.
  • Arrest of the action of food enzymes.
  • Prevention of purely chemical reactions in the food.

How to make these principles achievable

These principles can be achieved by doing the following:
  • Removal of heat from food and maintaining the food at a very low temperature as a refrigerator and deep freezing.
  • Removal of moisture from the food by drying. Drunk and takes place in the sun, artificial dryers such as oven, smoking, or free-drying.
  • Removal of air by vacuum sealing in bottles or cans.
  • Prevention of chemical reactions by addition of specific chemicals e.g antioxidants.
  • Inactivation of food enzymes that heating, addition of chemicals and removal of moisture.
  • Destruction of microorganisms by addition of chemicals.
  • Destruction of microorganisms by heat e.g. pasteurization and sterilization.

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Lesson Summary / Test

  1. Define the terms “Food Spoilage and food preservation”.
  2. What are the causes of food spoilage?
  3. How many categories of foods do we have? Mention them with examples.
  4. Why do we preserve foods?
  5. State the principles of food preservation.
  6. In what ways can we make food preservation principles achievable?
  7. State how you would preserve your foods according to the categories they belong.
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