New devices can improve traditional culinary techniques.
COOKS FILTER STOCKS TODAY just as they did in the Middle Ages: They put the bones and vegetable matter in a conical strainer known as a chinois (or China cap) and press it with a pestle or a ladle to squeeze out as much liquid as possible. Naturally the effectiveness of this procedure is limited by the size of the mesh of the chinois. A fine cloth liner helps, but it has to be cleaned after every filtering. Can’t we devise a more modern and efficient method? Looking to chemical laboratories for inspiration would be a useful first step on the road to culinary innovation.
Filtration in the Lab
The chief problem encountered in making a good stock is primarily a question of filtration: What is the best way to make a cloudy liquid clear? Traditionally clarification has been achieved by stirring a few egg whites into the cold stock and then heating the mixture over a low flame so that, when they coagulate, the whites trap the solid particles suspended in the liquid. Straining the mixture through a chinois lined with linen completes the process.
This procedure is unsatisfactory because it robs the liquid of a part of its flavor. Some chefs therefore add vegetables and fresh meat, cut into small pieces, along with the egg whites, to restore the flavor lost through clarification–a costly business. Imagine going to the trouble of cooking a stock for several hours and then having to re-enrich it because cooking has impoverished it.
Chemists, for whom filtration is a daily activity, solved this problem long ago with the aid of various devices adapted to specialized purposes. Indeed, the catalogue of one leading supplier of laboratory equipment today devotes more than forty pages to such devices. One of the most commonly used models has a funnel equipped with a fritted glass plate (which, unlike paper filters, does not tear) containing pores of uniform size. The matter to be filtered is deposited in the funnel, and the funnel is then placed on top of a conical vial in which a vacuum has been created by means of a waterjet pump, an inexpensive device that attaches directly to a faucet.
Antoine Westermann, the chef at Buerehiesel in Strasbourg, and I tested this apparatus with a tomato consommé that he wanted to be perfectly clear. The original recipe called for cooking the tomatoes in water to which egg whites had been added. After a half hour of slow cooking, straining the mixture through a cloth-lined chinois yielded a golden liquid. The laboratory device, on the other hand, yielded both a clearer liquid and a more pronounced taste. What prevents the makers of electric household appliances from producing this piece of equipment on a large scale? They would have only to increase the filtration capacity of the laboratory device and replace the glass with metal that will stand up to rugged use in commercial and home kitchens.
Other culinary uses for waterjet pumps can readily be imagined as well. Nicholas Kurti thought to use one to produce a new kind of meringue. Classically one makes meringues by adding sugar to egg whites that have been beaten until they are stiff and then cooking this mixture over very low heat. The coagulation of the proteins in the egg whites conserves the alveolar structure of the “floating islands,” while the water slowly evaporates, leaving a vitreous sugar residue. Kurti had the idea of substituting vacuum storage for heating. In this case the water evaporates while the dilation of the air initially present in the bubbles causes the meringues to greatly expand. The final result is light and airy—like “wind crystals.”
From Meringue to Soufflé
Although it has the virtue of showing how vacuum techniques can be used in cooking, this procedure is not altogether satisfactory, for the new meringues are too light and airy—there’s nothing to bite into. On the other hand, we can increase expansion and have something left to eat afterward if we choose a preparation in which the walls between the bubbles are thicker than in meringues. Soufflés and cream puff pastries come to mind as attractive candidates.
If one combines the ingredients needed to make a soufflé—flour, butter, milk, and eggs—in a vacuum bell jar the mixture swells up when the air is pumped out, for the air bubbles in the preparation expand, but the soufflé collapses when it is put back in atmospheric pressure. To prevent this from happening one needs to cook the soufflé in its expanded state—for example, with the aid of an electric heating element wrapped around the ramekin—in the vacuum bell jar. Heating it in this way causes the proteins to coagulate and the bubbles to swell up with water vapor, so that the soufflé preserves its structure when it is put back in atmospheric pressure.
No doubt many other uses for vacuums will be found once cooks decide to exchange medieval for modern equipment.