Test for proteins

Class: 3ème

Lesson: Les ailments

Rationale: Test for the presence of proteins in food samples.

Materials:

10% NaOH (available at Bangui paint stores. Ask for "soude caustique". As a solid NaOH is very hydroscopic so store in an airtight container.)

1% Copper sulfate (science kit)

needle and 5 ml syringe (for measuring; available at any pharmacy.)

eye dropper (science kit)

glasses

Suggestions for sample:

Positive: milk, peanut butter

Negative: manioc flour, banana, orange juice

Procedure: To prepare solutions:

1. 10% NaOH- 8 gm (or 1.5 tsp) of NaOH in 100 ml of filtered water.

2. 1% Copper sulfate- 1 gm (or 118 tsp) of copper sulfate in 100 mls of filtered water. It will be a very faint blue.

In class:

3. For liquids (ie., milk, orange juice) put about I ml in a clear glass. For solids (ie., peanut butter, flour, banana) mix or mash in 1 ml of water.

4. Add 1 ml of 10% NaOH and mix by swirling.

5. Add ~5 drops of 1% copper sulfate (or enough to give a nice color change.)

6. A violet color indicates the presence of proteins.

Source: Mackean Class Experiments in Biology, p. 14; Teacher's Book, p. 4, 21.