What is aeration?

Aeration is the abillity to entrap air. In relation to food e.g. whisking egg whites for a soufflè, the addition of sugar helps aeration which occurs when the egg whites are whisked. The mechanical action of the electric beaters produces heat by friction (the rubbing together) which causes denaturation or unfolding of the polypeptide chain within eggs.

This change is irreversible. Friction and heat produced by the electric whisk slightly coagulates (sets) the protein around the air bubbles. A soufflè will rise to a height because of air trapped in whisked egg whites. A small amount of salt or sugar helps to make the whites more stable and so will help trap the air for longer. The egg whites should be whisked until they form stiff but billowing peaks but not dry peaks. If overbeaten they will be very dry and not fold into the sauce. The egg yolk is mixed with a wooden spoon. The gradual addition of sugar alongside mechanical action assists denaturation of the egg yolk.

A 'bain Marie' consists of placing a container (for example, a pan, bowl, ramekins or soufflè dish) with food in a large, shallow pan of warm water on the hob. The water surrounds and protects delicate foods from direct heat, alowing them to be prepare "low and slow" because foods such as chocolate can burn easily from direct heat. The sauce in a "bain Marie' is then allowed to cool. The egg yolk is then mixed into the cool chocolate. If hot, the egg proteins would curdle or begin to cook in the sauce. Once the egg whites are whisked, they are folded carefully into the base sauce to maintain air in the mixture.

The soufflè is placed on the lowest shelf of the oven allowing it to rise upwards within the heat of the oven. As cool air enters the oven (alongside cool air in the soufflè) it's warmed, becomes less dense and rises thus pushing up the soufflè. When the filling the souffè dish, it's important to leave 2cm from the top of the dish otherwise the base wll swell; the soufflè will run over the sides and not have time to set. Onced placed in the oven the proteins livetin, vitellin, ovalbumin and globulin will coagulate.

Coagulation is the setting of the egg proteins. This happens at 65oC for egg whites and between 65-70oC for egg yolk.Coagulation of the egg proteins and baking at the correct tempreature for the correct time allows the soufflè to set as it rises.