Prac Exam: Food Tests

Question 1

Glucose

1. Reagents
2. Method
3. Positive results

Answer 1

1. Benedict solution
2. Method:
   - Add 5 ml of food type into test tube
   - Add Benedict solution until test tube is half full
   - put test tube in water bath
   - wait a few minutes
3. Orange = large quantity. Yellow = moderate. Green = very little.

Question 2

Starch

1. Reagents
2. Method
3. Positive results

Answer 2

1. Iodine solution
2. Method:
   - add a few drops of iodine solution to specimen
   - note any colour change
3. Blueish-purplish colour

Question 3

Lipids:

1. Reagents
2. Method
3. Positive results

Answer 3

1. Ethanol or ether
2. Method:
   - Mix specimen with quantity of ethanol
   - Decant liquid part and mix with water
   Or
   - Shake specimen with quantity of ether
   - pour liquid over filter paper
   - allow ether to evaporate
3. Liquid has milky appearance or a fatty stain will remain

Question 4

Proteins

1. Reagents
2. Methods
3. Positive test

Answer 4

1. Biuret test
2. Method:
   - grate the test material
   - shake up in water and boil
   - let it cool down
   - add 1 or 2 drops of copper sulphate
   - add excess amount of sodium hydroxide
3. Contents change to violet or pink