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The Science of Egg Whites

The Science of Egg Whites

A look at the science of egg whites: whoever considers it a "less noble" ingredient than the yolk is mistaken, and here's why.

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Pancakes, omelettes, cakes, meringues, macarons: these are just some of the delicious treats that owe their incomparable taste and aroma to egg whites, referred to in jargon as the “less noble” parts of eggs owing to the fact that they do not contain any of the precious fats and vitamins of the yolk.

Egg white nutrition facts

In actual fact, the albumin and yolk are two foods that could not be more diametrically opposed to each other, but we shall soon discover the many virtues of egg whites. The first lies in its composition: the albumin represents about two thirds of the total weight of an egg. On its own, the egg white has a water content of approximately 92%, while the remainder is largely made up of proteins and smaller quantities of minerals, vitamins, fats and glucose.

The main protein is ovoalbumin, or OVA. To date, its function is still unknown, but the most likely theory is that it serves as a sort of “storehouse” for the embryo proteins contained and developed within the egg. OVA is responsible for most of the characteristics of the albumin, its structure in particular. Ovoalbumin in fact is a serpin, that is to say, it belongs to the superfamily of ball-shaped proteins. When the OVA is heated, the links determining this structure break up and it takes on a more linear form, called beta-sheet. The beta-sheet exposes the hydrophobic regions that shun water, causing the proteins to solidify. Consequently, the egg white becomes solid.

What to do with Egg whites

You are already very familiar with this result, especially if you are fond of fried eggs. But there is another way to unfold the “balls” of ovoalbumin: by whisking it rapidly. What happens in this case is rather strange: since no cooking process takes place, as in the previous example, the water does not evaporate but remains in the bowl; the hydrophobic regions move away from the water molecules, while the hydrophilic ones, which love water, come closer. For this reason, the OVA forms a structure that puts the hydrophobic regions into contact with the air, entrapping a great many air bubbles. This produces “whisked” egg whites, which are actually nothing but froth.

However, if we want this “froth” to be stable and compact, the eggs have to be fresh (and therefore less alkaline) and at room temperature. Beware also of traces of yolk, which could ruin the structure created by the ovoalbumin. This leads us to a delicious practical application of the egg white theory: macarons. The symbol of French patisserie, these little cakes were actually first created in Venice and owe their crumbly consistency to egg white.

How to cook egg whites: macaron recipe

To make some delicious macarons, take 200 grams of egg white, 200 grams of ground almonds, 350 grams of icing sugar, 30 grams of 00-type flour, 70 grams of sugar and some natural food colourings. The filling is up to you but a delicious version can be made from 250 grams of mascarpone, 60 grams of icing sugar, 250 grams of fresh cream and any jam of your choice. Mix the almonds, sugar and icing sugar in a bowl. Separately, whisk the egg whites until they are stiff and add the mixture you have previously prepared, folding it in very gently. When everything is well blended, divide the mixture into two batches and add the colouring.

At this point, using a piping bag, shape as many small disks as possible onto a baking tray lined with greaseproof paper. Let the macarons rest for an hour and a half. In the meantime, prepare the filling ingredients. Bake the macarons for 10-12 minutes in an oven preheated to 160 °C, then remove and leave to cool. Fill half of the disks with the cream filling and the other half with jam, before uniting the two types. And while you are feasting on them, without being able to stop, remember that most of the credit has to go to the precious egg white.


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