Practicals

Question 1

What are the seven food groups

Answer 1

• vitamins
• minerals
• fibre
• proteins
• fats
• carbohydrates
• water

Question 2

What is the use of the iodine solution test

Answer 2

It is the test for starch

Question 3

What is the use of the Benedict’s solution test

Answer 3

It is the test for reducing sugars

Question 4

What is the use of the biuret test

Answer 4

Test for proteins

Question 5

What is the use of the ethanol emulsion test

Answer 5

It is the test for lipids (fats and oils)

Question 6

What is the positive and negative results of a iodine solution test for starch

Answer 6

Positive - colour changes to blue-black colour
Negative - colour stays browny-orange

Question 7

What is the positive and negative results of a Benedict test for sugar/glucose

Answer 7

Positive - range of colours which show you the concentration of reducing sugars
green- trace
yellow- low
orange- moderate
brick red- high

Negative - light blue

Question 8

What is the positive and negative results of a Ethanol emulsion test for Lipids

Answer 8

Positive - cloudy emulsion
Negative - colourless

Question 9

Emulsion

Answer 9

When one liquid doesn’t dissolve in another it just forms little droplets

Question 10

What is the positive and negative results of a biuret test for proteins

Answer 10

Positive - purple
Negative - blue

Question 11

Method for Iodine test for starch

Answer 11

1. Place food samples on spotting tile
2. Number each sample
3. Add two drops of iodine solution to each sample
4. Record color of solution
   - safety: safety goggle + lab coat

Question 12

Method for Biuret test for Protein

Answer 12

1. Place sample food in test tubes and number them
2. Add 2 cm^3 (20 drops) of biuret reagent to samples (if food is dry add 5 drops of distilled water)
3. Record color of reagent
   - safety: safety goggles + lab coat

Question 13

Method for Emulsion (ethanol) test for Lipids (fats)

Answer 13

1. Place food samples in a test tube and number them
2. Add 2 cm^3 (20 drops) of ethanol to the food samples
3. Shake the tube for 10 seconds
4. Pour sample into tube of distilled water
5. Record the color of reagent
   safety: safety goggles + lab coat

Question 14

Method for Benedict’s test for reducing sugars

Answer 14

1. Place food samples in a boiling tube and number them
2. Add 2 cm^3 (20 drops) of Benedict reagent to food samples
3. Place the tube into a boiling water bath (carefully)
4. Leave for 3-4 minutes
5. Remove carefully with a test tube holder
6. Record color of the reagent
   - safety: safety goggles + lab coat + avoid contact with skin