Stability of egg white foams

Object:  To study the effect of various additives on the stability of egg white foams.

Materials

• 5 plastic bowls
• Electrical beater, hand-held, or food processor
• 5 x 25 ml measuring cylinders
• 5 filter funnels
• Glass wool
• 2 weighing boats
• 2 plastic pipettes
• 2 plastic spoons
• Egg white
• Vegetable oil
• 10% citric acid
• Cream of tartar
• Salt

Method

Number the bowls.  Measure and transfer 25 ml of egg white into each bowl, then make the following additions:-

• No.1. no addition
• No.2. 1 ml citric acid
• No.3. 0.5 g cream of tartar
• No.4. 0.5 g salt
• No.5. 1 ml oil

Beat each sample for four minutes with the beater at the middle speed setting.  It is important that each sample be given exactly the same treatment.  Observe and record the quality of the foam.  

Carefully transfer the contents of each bowl into the filter funnel with a plug of glass wool set in the measuring cylinder.

Leave for 30 minutes and then record the volume of the drip.  The greater the volume of drip, the less stable the foam.  Tabulate the results.

In addition to commenting on your results in the normal way, you should also answer the following questions:-

• Describe 3 operations in catering in which egg white foams are important
• In what ways will this experiment help you achieve better results in the kitchen?
• What would you consider to be the limitations of this particular experiment?
• Suggest other experiments that you think would provide useful information about egg white foams.