Testing for Sugars, Starch, Proteins and Fats

Question 1

What reagent do we use to test for sugars? What happens in the presence of sugar?

Answer 1

1. Benedict’s solution

2. Experiences a colour change from light blue to orange to brick red (when heated)

Question 2

What reagent do we use to test for starch? What happens in the presence of starch?

Answer 2

1. Iodine or potassium iodide solution

2. Experiences a colour change - reddish-brown to blueish-black

Question 3

What reagent do we use to test for proteins? What happens in the presence of protein?

Answer 3

1. Biuret solution

2. Experiences a colour change - colourless to lilac

Question 4

What reagent do we use to test for fats? What happens in the presence of fat?

Answer 4

1. Ethanol

2. White solid precipitate forms, due to the fat binding to the ethanol.