Delicious emulsions that can be made from any vegetable, meat, or fish.
WE START WITH AIOLI—the real article made in Provence by adding olive oil to crushed garlic, without the benefit of egg yolk. It is an emulsion, which is to say a dispersion of oil droplets in water, supplied in this case by the garlic. Why should this sauce be stable, whereas normally a mixture of oil and water separates? Because garlic contains tensioactive molecules that coat the oil droplets and prevent them from fusing. Aioli is a relative of mayonnaise, in which the protein molecules and phospholipid lecithins of the egg yolk are tensioactive.
Let’s try varying the traditional recipe a bit. Does the shallot, which belongs to the same vegetable family as garlic, also contain tensioactive molecules that permit us to make an “échalatoli”? Can an “oignoli” be made from onions? The experimental response is conclusive: Adding oil to crushed shallots or onions does in fact yield such emulsions. In the worst case it is necessary to add a little water (just as, in certain recipes for aioli, adding a piece of bread soaked in milk is recommended). It remains for cooks to dream up new dishes that these sauces could accompany.
But are there vegetables other than the ones of the lily family that could serve the same purpose? After all, cooks know that mustard can be used to make emulsioned vinaigrettes, for mustard also contains tensioactive molecules that help to stabilize the sauce.
The Virtues of Membranes
The answer is simple if we recall that all cells, whether plant or animal, contain compartments of water and proteins that are bounded by membranes. These membranes are composed of phospholipid molecules having a water-insoluble lipidic tail and a water-soluble head. In living cells these phospholipid molecules form double layers because the hydrophobic tails are grouped together inside the various cellular compartments, whereas their hydrophilic heads are in contact with the water outside the compartments. Phospholipid molecules are abundant and have strong tensioactive properties. Can they be used to thicken an emulsion?
Let’s try crushing a zucchini and adding oil to it, drop by drop. The result is a thick sauce that, by analogy once again, we may call “courgettoli.” Why not move on next from the plant to the animal kingdom, because animal cells also contain membranes? If we crush a cube of beef and add some oil, we find that we obtain “bœufoli.” From any vegetable or animal, then, we discover that we can make an emulsified sauce as long as we release the phospholipid molecules, for example by crushing them and adding oil (again, a bit of water must be added at the outset if the chosen ingredients contain too little of it).
Phospholipids are not the only tensioactive molecules in plant and animal cells; many proteins have good emulsifying properties as well. Whisking oil into an egg white forms a remarkably stable emulsion but with very little flavor. More interesting sauces can be made from meat, fish, and vegetables, whose protein molecules likewise contribute to their stability.
New Mousses
From emulsions we turn now to an analogous physical system, foams, which consist of air bubbles dispersed in a liquid or solid. The fact that a chocolate mousse can be obtained by whisking a chocolate emulsion, as we shall see later in this section, suggests that it may be possible to generalize this procedure.
We might try using cheese, for example. Cheese contains a great amount of fat and tensioactive molecules, or caseins, which disperse the fatty droplets throughout the milk. To produce a cheese mousse, first make a cheese emulsion, heating a pan and then adding water and small rounds of goat cheese (Chavignol, for example). Shake the pan gently. The result is a smooth, thick sauce that under the microscope can be seen to be composed of droplets dispersed in water (for a sharper taste one can substitute vinegar for the water and reduce it over high heat). This preparation we may call a “cheese béarnaise.”
To obtain the desired mousse, use the same procedure that turns cream (an emulsion of milk fats in water) into whipped cream: cooling followed by whisking. In this case you put the pan in the freezer for about ten minutes and then whisk the chilled sauce vigorously to make what might be called a Chavignol Chantilly. The same method can successfully be used with Roquefort to yield a Roquefort Chantilly, and so on.