Cracked wide open: Swetha Sivakumar on cooking with eggs

The egg can be a cook’s best friend in the kitchen, and their greatest challenge. Making the perfect omelette is so hard, it is often used as a test of a chef’s expertise. It can take years to learn to replicate the precise cigar shape and silky yellow texture of the French omelette, eliminate all brown spots and that eggy smell.

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A boiled or fried egg, on the other hand, is one of the first dishes a child might make at home. Break one over hot oil and one generally cannot go wrong.

How does this little orb manage to be both so simple and so complicated? Let’s take a look.

The egg is made up of two very different components. There are the whites, which are 90% water and about 10% protein, with trace amounts of minerals, vitamins and glucose. And the yolks, which are about 50% water, 34% fat and 16% protein. The yolk, incidentally, is packed with vitamins and minerals, including iron; essentially, all that would be necessary in order to grow a chick.

There are two key things to understand when it comes to cooking an egg. The first is that the water molecules outnumber the proteins in a ratio of about 1,000:1. But the proteins are giant molecules made up of thousands of atoms folded into a compact shape. As heat is applied, they unfold, reach out to each other and coagulate to form a tangled network. The water is now trapped in this network.

The protein starts to coagulate at 65 degrees Celsius in egg whites and 70 degrees Celsius in yolks. If the temperature continues to climb, the aggregates cluster more closely, pushing the water out. This makes the result rubbery, and gives the dish an “eggy” smell.

That smell comes from ferrous sulphide, which is formed when the sulphur in the egg-white’s albumin protein reacts with the iron in the yolk. This is also why an egg boiled too long develops a greenish-grey ring around the yolk. To avoid the smell, use fresh eggs. They are less alkaline, which makes conditions less favourable for this reaction. Also use lower temperatures while cooking, and don’t cook for too long.

Now for the separation. Get the whites away from the yolks and the possibilities expand exponentially. This is because each of them has distinct superpowers. The whites can puff up eightfold when whisked, and thus function as a greater leavener, helping to add volume to baked goods. They fluff up, once again, because of those large protein molecules. As the whites are whisked, the molecules stretch out, reach out to each other, and form a network that traps air and water.

Yolks, on the other hand, are great emulsifiers. Each one is essentially a bag of fat, protein and water. The fat and water wouldn’t normally stay together so cohesively, but they do because of the presence of a chemical compound called lecithin. Add pure yolk when making foods such as mayonnaise, ice-cream and custard and the lecithin keeps it all together, making the end result smooth and silky.

Acid adds another layer of complexity. Recipes often recommend a dash of vinegar when poaching or cream of tartar when whisking whites. This is because, in raw form, the curled-up protein molecules have their positive and negative charges dispersed in a carefully designed pattern. Acids contain an abundance of positively charged protons. Add one to the mix and the protons wreak havoc in the protein’s neatly designed structure. They end up partially unfolding and coagulating some of the protein, especially on the surface. This is why a dash of acid helps to partially set egg whites.

Combining the superpowers of the whites and the yolks is possible, but tricky. In a souffle (from the French souffler, for puffed up or inflated), the fluffiness of the egg whites melds with flavour components held together by yolks. Cook the airy mix at too high a temperature, though, and pressure builds and the souffle collapses. Mix the batter too thin and it will rise and fall more easily and unpredictably; make the batter too thick and it will not rise much at all. It’s an experienced baker who can make a souffle the same way each time.

Baking instructions can help, or they can feel overwhelming. They are much easier to implement when one has understood the science behind them. I hope I have helped with that!

(To reach Swetha Sivakumar with questions or feedback, email [email protected])