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Eggs are often used in cooking in order to incorporate air
into a mixture and hold it there, as in soufflés, meringues
and cake mixtures. This property of eggs is called aeration.
When air is incorporated by whisking, whipping or beating,
the air bubbles in the liquid become coated with protein;
the molecules uncoil (denature) so that they extend and surround
the globules of air to create and stabilise the foam.
Egg whites have good foaming properties as
they contain a number of different proteins with the desired
properties and perform best at a temperature of about 14°C.
Traces of fat will inhibit foaming properties as fat is present
in egg yolks, contamination with even small amounts of yolk
has to be avoided for the best results.
Egg yolks do not foam readily.
Whole egg foams are denser than egg white
foams. In this the egg yolk becomes part of the foam, in spite
of its fat content, because the fat becomes emulsified. The
volume is increased when whisking takes place over steam heat
at 80°C.
Without the aeration property of eggs, many of our traditional
dishes would not have the desired texture.
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- 6 eggs (large)
- 120g caster sugar
- Cream of tartar (tartaric acid) - 1 pinch to make
6 pudding bases
- 4 slices wholemeal bread (made into breadcrumbs)
- 6 teaspoons caster sugar
- 300ml milk
- 6 teaspoons jam
- 6 foil dishes - 10cm diameter (approximately)
- Measuring jug
- 6 small basins
- Rotary whisk or electric whisk
- Tablespoon
- Dessertspoon
- Teaspoon
- Fork
- Kitchen knife
- Chopping board
- Baking sheet
- Egg separator (optional)
- Stopclock
- 6 small sticky labels
- Pens or pencils (6 different colours)
- Teatowel
- Dishcloth
- Ovengloves
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Heat oven,
200°C, gas mark 6. Adjust shelves so that one shelf
is two-thirds of the way up the oven. |
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Divide breadcrumbs evenly
between the six foil dishes. |
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Place dishes on a baking
sheet. |
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Measure 50ml milk into
a measuring jug. Add 1 teaspoon caster sugar. |
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Separate the first
egg. Place the white in a basin and place the yolk in
the measuring jug with the milk. |
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Whisk egg and milk with
a fork. Pour over the bread in the first foil container.
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Repeat stages 4-6 with
the remaining 5 eggs. |
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Place all six foil containers
in the oven for 15 minutes. |
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When firm and set, remove
the dishes from the oven and spread 1 teaspoon of jam
over the surface of the mixture in each dish.
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Take the first egg white.
Whisk until the foam is firm, with pointed peaks, but
not dry or brittle. Record the time taken.
NB: As
a test, the bowl may be cautiously inverted over the
work surface.
The correct texture has been obtained when the white
remains in the inverted bowl.
Time taken:
seconds
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Place the meringue on
top of the mixture in the first foil container. Make
a label to indicate that there were no additions to
the foam - this is the control.
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Stick the label under
the base of the dish: place the dish on the baking sheet. |
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Repeat stages 10-12,
according to the following table of instructions, being
sure to label each dish appropriately and accurately.
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Bake the meringues for 15 minutes until
lightly browned. |
White
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Whisking
time
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Special
Instructions |
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Until bowl may be
inverted
(Record time)
seconds |
Add 40g sugar before
whisking begins |
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Until bowl may be
inverted
(Record time)
seconds |
Whisk in 40g sugar
when the bowl can be inverted |
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Until bowl may be
inverted
(Record time)
seconds |
Weigh out 40g sugar. Whisk in 1 teaspoon of sugar when
bowl can be inverted. Then fold in the remaining sugar
with a tablespoon
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Until bowl may be
inverted
(Record time)
seconds |
Add 1/2 teaspoon of
egg yolk before whisking begins |
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Until bowl may be
inverted
(Record time)
seconds |
Add 1 pinch of cream of tartar before
whisking begins |
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Examine
the cooked foams one at a time. Judge each on its own
merit - do not compare the foams or their attributes
at this stage.
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Carefully take out a
spoonful of cooked foam. Consider:
- Texture
- Appearance
- Taste
- Overall acceptability
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Repeat for remaining
foams. |
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Carry out hedonic ranking
on each foam using the grid on the next page to record
your results. Using a different colour pencil for each
foam, mark on each axis the number which best corresponds
to how you feel about each attribute of each foam.
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Use this five point
scale:
1 like
extremely
2 like
moderately
3 neither
like nor dislike
4 dislike
moderately
5 dislike
extremely
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Join the points for
each foam to produce a profile for each foam. eg
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- List the descriptors which you feel best describe the
perfect meringue topping:
- Which foam was most successful?
- Which foam was least successful?
- Using the information from your results, give stage instructions
for making a meringue topping
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