The Science of Eggs

Eggs are an integral ingredient in a lot of pastry and cakes, contributing to the fluffy and spongy texture of cakes. It is important to understand the basic science every time you bake a cake. Egg whites are the most versatile and complete naturally occurring protein source. When you whip the egg whites, you are disrupting the protein and the volume of the beaten whites increase up to eight times. Whipping or whisking introduces air into egg whites and the air is surrounded by liquid. Egg protein is made of coiled up amino acids strung together because the individual amino acids have electrical charges. When egg whites are beaten, the beating action stretches and uncurls proteins, causing the proteins to form elastic films around air bubbles and essentially trapping them –  this is what we refer to as foam.

 

Eggs White – When the foam is heated, the trapped air bubbles eventually expand and if baking soda or baking powder is used, carbon dioxide will be released causing the batter to rise further. Egg protein will eventually coagulate around the air bubbles giving the foam a permanent shape. Egg protein can be beaten to 4 stages of stiffness, each stage will contribute to a different texture in the final product.

 

1. Soft Peak

The air bubble is getting smaller after air is introduced into the protein, the foam is white and flowing. As you lift up the whisk, the egg white forms a peak for a brief moment and then the tip folds over, this consistency is usually suitable for making cheesecakes as the protein is “soft” enough for cheese to be incorporated.

 

2. Stiff Peak

The foam has reached its maximum volume, the tip stays stiff with a pointed end as the proteins are stretched to maximum. This is the most useful stage for egg whites as it is used in all recipes that call for chiffon or sponge.

 

3. Hard Peak

The foam is characterised by a hard peak that is very short and firm, some recipes of meringue call for this stage of egg whites as it is suitable for making pie toppings or dry meringue cookies.

 

4. Over-Beaten Peak

If you further whisk the foam, the proteins will break up and the foam is no longer moist and shiny. The egg whites look dry and clumped up and because of the dryness are suitable to be made into pastries, for example waffles, that have a crispy texture.

 

 

Egg Yolk (Lecithin) – Is responsible for the egg's emulsifying properties due to the fat and lecithin it contains which also contributes to the fine and smooth texture of cakes and pastries by emulsifying water and oil ingredients together. Egg yolks contain extra nutritional properties such as selenium, omega-3, vitamin E, A and other minerals.

 

Sugar – Sugar interacts with egg proteins to stabilise the whipped foam structure. Sugar makes the egg foam more elastic by pulling the moisture from the foam and allowing it to set better, sugar also allows air cells to expand better when gases are released from the leavening agent. Apart from that, sugar also delays moisture escape from the egg white foam and this allow the cake to rise and set in the oven. That explains why meringue is sweet – it needs sugar to stabilise the structure without using flour. Sugar should be added gradually after egg whites are whipped until frothy.

 

THE SIZE AND WEIGHT OF EGGS IN THE MARKET:

AA – 70 g and Above

A – 65 g to below 70 g

B – 60 g to below 65 g

C – 55 g to below 60 g

D – 50 g to below 55 g

Size B & A are usually prefered for baking due to standard egg protein content.

* Source from Federation of Livestock Farmer's Association of Malaysia.

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