Lesson Notes By Weeks and Term - Senior Secondary 1

Scientific study of foods

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Term: 2nd Term

Week: 1

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes

Date:       

Subject:      Food and nutrition

Topic:-       Scientific study of foods

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. State the characteristics of the various classes of food

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S ACTIVITY

STEP 1

INTRODUCTION

The teacher reviews the previous lesson on absorption of food nutrients

Students pay attention

STEP 2

EXPLANATION

She states the characteristics of each food nutrient

Students pay attention and participates

STEP 3

DEMONSTRATION

She lists the sources of each food nutrient

Students pay attention and participate

STEP 4

NOTE TAKING

The teacher writes a summarized note on the board

The students copy the note in their books

 

NOTE

THE SCIENTIFIC STUDY OF FOOD NUTRIENTS

CHARACTERISTICS OF FOOD NUTRIENTS
The quality and value of any food depends on the nutrients it contains. It is therefore necessary that you understand the characteristics of the nutrients and the effects of heat on the nutrients.

SUB-TOPIC 1: CHARACTERISTICS OF FOOD NUTRIENTS
Food nutrients are simple, chemical substances which are available in the food we eat. The various food nutrients differ from each other in their physical and chemical properties.
(i) Physical Properties: These include their structural appearances. The physical properties of a food may change when it is treated in certain ways.
(ii) Chemical Properties: These include the chemical compositions of the nutrients. This means the units of elements, groups of elements that make up the nutrients and how they behave under certain conditions.

PROTEINS
Proteins are body builders. They are important for building and repairing body tissues. Sources include fish, eggs, meat, poultry, milk, beans etc.

  1. Characteristics of Proteins
    Proteins are made up of chains of amino-acids.

  2. They contain these elements; carbon, oxygen, hydrogen and nitrogen.
  3. Some proteins also contain small amounts of sulphur or other elements.
  4. The final products of protein digestion are the amino-acids.
  5. Proteins are digested by enzymes called protease.
  6. Most protein is insoluble in water.
  7. Some proteins possess an amount of elasticity [i.e. the protein can be stretched during preparation such as the gluten in flour during kneading]
  8. Many proteins are coagulated by heat.
  9. Protein is not destroyed by heat.

Carbohydrates
Carbohydrates are energy foods. They include starches, sugar and cellulose. Food sources include rice, maize, cassava, yam, millet, etc.

Characteristics of Carbohydrates

  1. All sugars are sweet, but they vary in sweetness. Sugars are soluble in water.
  2. They form crystals in dry form.
  3. Simple sugars are colourless. Starches are white in colour.
  4. They are soluble in water.
  5. Starches and complex sugars are broken down to simple sugars before animals can use them.
  6. Starches are often stored as starch, grains in plant cell.
  7. The last product of carbohydrate digestion is glucose. Dry heat causes sugar to melt into a brown honey like substances called caramel.
  8. The elements that make up carbohydrates are carbon, hydrogen and oxygen. These elements combine in different ways to form: simple sugars e.g. glucose, fructose; complex sugar e.g. lactose, starches e.g. cassava, rice, yam, cellulose, which is found in some vegetables.

Fats and Oils
Fats and Oils are energy givers like carbohydrates. Sources of Fat and oils include palm oils, margarine, butter, fatty meat, egg yolks, groundnut oil etc.

Characteristics of Fats and Oils

  1. They are bad conductors of heat.
  2. They help to insulate the body from cold and keep it warm.
  3. Fats and Oils are substances which do not blend with water but are soluble in either.
  4. Fats and oils are normally lighter in weight than water hence oil will float on top of water.
  5. Fats are solid at room temperature. Oils are liquid at room temperature.
  6. Fats have a poor keeping quality. When they are exposed to air for prolonged periods, they become rancid. This is spoilage as rancid Fats and
  7. Oils have an undesirable flavor and taste.
  8. They are broken down to fatty acids and glycerol before they can be absorbed by the body.
  9. They contain high proportions of carbon and hydrogen but very little oxygen.

Vitamins
Vitamins can be defined as organic compounds that are needed by the body and which the body cannot manufacture. The body requires a very small amount of these nutrients. Vitamins are grouped into two classes according to their characteristics; they are water and fat-soluble vitamins.

Characteristics of Vitamins

  1. Vitamins A and D: These are fat-soluble vitamins i.e. they are vitamins that does not dissolve in water or get destroyed by ordinary cooking. They are destroyed when the fat that contains them goes rancid i.e. spoiled. Examples are carrot, tomatoes and palm oil.
  2. Vitamins B: This is water-soluble, i.e. it dissolves in water. Food sources should be cooked with small quantity of water using a fast cooking method. Over cooking can lead to loss of vitamins. Examples are liver, yeast, milk, egg.
  3. Vitamins C: This is water-soluble, i.e. it is easily destroyed by heat and exposure to air. It can also be lost by soaking in water. Food sources should be cooked with small quantity of water using a fast cooking method. Examples are oranges, lime, pawpaw.

Minerals
These are substances which are needed by the body. The body requires a very small amount of these substances but it cannot produce them itself, and have to be supplied by the food we eat. Some of the essential minerals include iron, calcium, potassium, sodium etc. All minerals are soluble in water. Examples of foods that contain these minerals are: milk, cheese, egg, green vegetables, sea foods, table salt.

Water
Although water does not have any energy value, it is very essential to life and is present in considerable amounts in almost all the food we eat. Water is composed of hydrogen and oxygen in a ratio of 2:1.

 

EVALUATION:    1. Discuss the characteristics of each class of food

  1. List some sources of each class of food

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively