Q. Effect of various additives on the stability of egg foam?

• recognize the different stages in the foam formation,
• explain the effect of various factors in foam formation, and
• apply the concept of foam development in preparation of various food.

Principle

The two factors of utmost importance in egg white foams are stability and volume. Several factors influence one or both of these characteristics  The extent of beating is an important factor in stability of egg white foam. As beating progresses, the foam becomes increasingly stable up to a critical point, after which continued beating decreases stability.

Maximum stability is reached when the whites just bend over, but before maximum volume has  been reached. If beating  continues beyond the point of maximum stability, the surface begins to look  slightly  dry, and the foam exhibits some brittleness. Foam formation is  delayed when the whites are well below room temperature.

Procedure

Now carry out the experiment step-by-step as enumerated herewith:

A)  Preparation of white egg foam.

i)  Separate the white from the yolk egg.

ii)  Beat egg white to stiff peak using a rotary beater or a whisk and note the time taken for foam formation.

iii)  Transfer the prepared foam to a funnel lined with filter paper and placed over a measuring  cylinder. Keep aside for 45 minutes and record the volume of the liquid drained.

Use one egg white for each of the variations given below and carry out the variations B to I repeating the procedure of preparation of egg white foam as given above in A (i-iii).

B)  Add 1/8th teaspoon salt to egg white for preparing the foam.

C)  Add 1/8th cream of tartar and then beat.

D)  Add 1/4th of egg yolk and then beat  to attain the foam

E)  Add 10 ml of water and then beat

F)  Add 2 teaspoon of castor sugar and prepare the foam

G)  Add 10 ml distilled water and proceed

H)  Add 10ml oil and beat

I)  Use a different type of beater

After keeping the foams  for 45 minutes, compare the results of the samples A to I (total of 9 samples) with respect to time taken for foam formation, colour of the foam formed, stiffness, dullness or shiny texture and other sensory attributes to determine the most stable foam.

Precautions

1) Egg white should be separated carefully from the yolk so as not to mix even at trace of the yolk.

2) Beating should be done till the stiff peak stage only.

3) Added substances should be measured accurately.

4) Time should be noted when the stiff peak is reached.

5) All samples should be neatly labeled on completion and drained for exactly 45 minutes before observations are recorded.