Food Tests

Question 1

What is the method for testing reducing sugars?

Answer 1

1. Grind food and mix with a small amount of water. 2. Transfer 1-2 mL to a boiling tube. 3. Add 5 drops of Benedict’s solution. 4. Heat in a water bath (≥ 80℃ for 4 mins).

This test specifically identifies simple sugars like glucose and maltose.

Question 2

What color indicates the presence of reducing sugars in Benedict’s test?

Answer 2

Brick-red colour

A blue color indicates that reducing sugars are not present.

Question 3

What is the method for testing starch?

Answer 3

1. Grind food and mix with a small amount of water. 2. Transfer 1 drop to a spotting tile. 3. Add 1 drop of iodine solution.

This test identifies the presence of starch in food samples.

Question 4

What color indicates the presence of starch in the iodine test?

Answer 4

Blue-black colour

An orange-brown color indicates that starch is not present.

Question 5

What is the method for testing lipids?

Answer 5

1. Grind food and mix with a small amount of water. 2. Transfer 1 mL to a test tube. 3. Add 1 mL of ethanol. 4. Decant 1 mL into a test tube which contains 1 mL of water already.

This is known as the emulsion test for lipids.

Question 6

What appearance indicates the presence of lipids in the emulsion test?

Answer 6

Milky appearance

A transparent appearance indicates that lipids are not present.

Question 7

What is the method for testing proteins?

Answer 7

1. Grind food and mix with a small amount of water. 2. Transfer 1-2 mL to a test tube. 3. Add 5 drops of copper sulfate solution and 5 drops of sodium hydroxide solution.

This is known as the Biuret test for proteins.

Question 8

What color indicates the presence of proteins in the Biuret test?

Answer 8

Purple colour

A blue color indicates that proteins are not present.