Lesson Notes By Weeks and Term - Senior Secondary 1

Food tests

Get it on Google Play
Get it on the Apple App Store
  1. Home
  2. Lesson Notes By Weeks and Term
  3. Senior Secondary 1
  4. Food tests

Term: 2nd Term

Week: 4

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes

Date:       

Subject:      Food and nutrition

Topic:-       Food tests

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

  1. Explore the tests for different food nutrients

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 the effects of heat on food

Students pay attention

STEP 2

EXPLANATION

She discusses the tests for carbohydrates and proteins

Students pay attention and participates

STEP 3

DEMONSTRATION

She discusses the tests for Oils

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

FOOD TESTS.
TEST FOR PROTEIN
Millions Test:- The presence of protein in food can be tested by the use of a chemical called million reagents.

Procedure

  1. Place 1-3g of egg white or other ground protein in a test tube.
  2. Add about 4ml of water and shake.
  3. Add about 2.5ml of Millions reagent.
  4. Observe a white precipitate that will be formed.
  5. Place the test tube in a beaker that is half-filled with water.
  6. Heat the water gently.

Observation: The precipitate will turn red, indicating the presence of protein.

Burette Test:

  1. Obtain a small quantity of ground meat or egg white.
  2. Place in a test tube and mix with a few drops of water.
  3. Add about one cube centimeter (1cm3) of dilute caustic soda (NaOH) and mix well. Add, drop by drop, 1% copper (ii) sulphate solution.
  4. Shake thoroughly after each drop.

Observation: A purple or violet colour indicates the presence of protein.

TEST FOR CARBOHYDRATES
Test for starch (yam, potatoes, rice, maize etc)

Iodine Test
Procedure

  1. Get a slice of yam.
  2. Place it on a clean glass slide or flat plate.
  3. Add 1-2 drop of iodine solution to the cut slice of yam.

Observation: The yam turns blue-black in colour. This shows the presence of starch.

Fehling’s test
Test for simple sugars. (table sugar, honey, fruits e.g. ripe bananas)

Procedure

  1. Place about 5ml of 5% sugar solution in a test tube.
  2. Prepare the Fehling’s solution by adding equal amounts of Fehling’s solution. A (copper (II) sulphate in water) and B (sodium potassium tartrate and sodium hydroxide in water).
  3. Add 5ml of Fehling’s solution to sugar solution.
  4. Place the tube in beaker that has been half-filled with water.
  5. Heat the beaker gently to boiling point.


Observation: An orange or brick-red precipitate will be formed. This shows the presence of sugar.

Test for Oils
The Grease Spot Test

Procedure

  1. Rub or mark a little piece of butter of groundnut oil on a sheet of light, white paper.
  2. Hold up the paper.

Observation: A translucent patch is formed by the oil mark.

Sudan III Test
Procedure

  1. Place a small quantity of groundnut paste (or any other chopped or mashed food substance that contains fat) in a test tube.
  2. Add a few drops of Sudan (III) solution or osmic acid.

Observation: A distinct red colouration is produced

EVALUATION:    1. Discuss the tests for

  1. carbohydrates
  2. proteins
  3. fats and oils

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively