Lesson Notes By Weeks and Term - Senior Secondary School 2

SUBJECT: FOOD AND NUTRITION

CLASS:  SS 2

DATE:

TERM: 1st TERM

REFERENCE BOOK

• Food and Nutrition for SS 1-3 by Dr. J. O. Olusanya and others

 
WEEK 8

TOPIC: RAISING AGENTS

• Definition 
• Types and uses e.g. Air, Baking powder, Yeast etc.

Definition of Raising Agents.

Raising agents are substances that produce gas in flour mixtures which will make mixtures (e.g. cakes, bread, batters, pastries) rise and have a light pleasant texture.

Raising agents are used to introduce a gas into a mixture.

The gases used for the purpose are;

Carbon dioxide (C02) air (mixture of gases) 

Steam (water in a gaseous state) 

EVALUATION 

Define raising agents 

Types of raising agents raising agents fall into two categories.

Mechanical raising agents chemical raising agents.

Mechanical raising agents

Air is incorporated into mixtures by various mechanical methods, some of the methods are;

1. Sieving   
2. Creaming
3. Whisking
4. Folding
5. Rolling
6. Rubbing

1. Sieving – When flour is sieved air becomes trapped between it’s many fine particles.
2. Creaming – When fat and sugar are creamed together.  Air becomes trapped in the form of tiny bubbles.
3. Whisking – When egg white is whisked it can hold up to seven times it’s volume of air.
4. Folding & Rolling

    This is used for flaky pastry.  Air is trapped between the layers and it is sealed in 

5. Rubbing - in

    Some air is trapped as the fat is rubbed into the flour.

Chemical raising agents.

Carbon dioxide is incorporated into mixtures by the use of:

1. Bicarbonate of soda alone.
2. Bicarbonate of soda plus an acid.  Baking powder contains bicarbonate of soda and acid.

Yeast is not strictly a chemical method as yeast is a living organism.

Yeast

Yeast are microscopic single – celled fungi which are found in the air and soil and on the surface of fruits.

Yeast cells reproduce by budding.  In order for them to reproduce they need a supply of water, warmth and 

food.  The cells remain dormant in very cold condition and are killed at temperatures approaching 1000C.  

Growth is inhibited by high salt concentration.

Palm wine

This is a good raising agent for it contains yeast.  It is used for commercial bread making and it is more 

economical than yeast.  Warmth, sugar and moisture are necessary conditions for it’s raising action like yeast.

Excessive heat and cold and too much salt or sugar retard their growth or stop their growth.

EVALUATION

Classify raising agent.

READING ASSIGNMENT

Raising agents

Reference Book – Foods and Nutrition for SS 1-3 page 103-104

WEEKEND ASSIGNMENT

1. _____ are substances that produce gas in mixture.

    (a) Salt               (b) Pepper    (c) Raising agents

2. Raising agent are classified into ________

    (a) three    (b) ten        (c) two

3. _____ reproduce by budding.

    (a) Air        (b) Yeast    (c) Baking powder

4. _____ is an example of chemical raising agent.

    (a) Creaming    (b) Whisking    (c) Baking powder

5. _____ is an example of mechanical raising agent.

    (a) Sieving    (b) Yeast    (c) Bicarbonate of soda

THEORY

1. Define raising agent.
2. Classify raising agent and give two examples of each.