Emulsions: The Mystery and Science Behind Getting it Right
Day four of Culinary Skills II was the big day of preparing Hollandaise. A rich, buttery sauce with a hint of lemon, hollandaise receives praise for its unforgettable flavor when it’s served warm over steamed asparagus, a pan-seared fish or a plate of eggs Benedict. Hollandaise also seems to cause faces to adopt a look of worry for those embarking on the adventure of preparing it. When day four had finally arrived, I was wondering what all the fuss was about. Why does the preparation of hollandaise get such a bad rap? What is it about the delicious and savory sauce that causes people to get psyched up to prepare it?
What I learned right away is that hollandaise is an egg-thickened sauce that’s contents work together by emulsion. An emulsion is a combination of two liquids that usually do not go together, such as oil and water. In the case of hollandaise, the two liquids are melted butter and water (this includes the water within the lemon juice in a classic hollandaise sauce). Ordinarily, if one puts melted butter and water together in the same container, the two ingredients will not blend. Instead, the oil ingredient forms tiny droplets which are surrounded by the water and can create a grainy looking sauce. In order for these two ingredients to combine successfully into a creamy, smooth sauce, a third ingredient is needed. This third ingredient is called an emulsifier and many foods can act as emulsifiers. Egg yolk is the most popular emulsifier, and egg whites, gelatin and even skim milk are also known to play this role. These foods are also referred to as chemical emulsifiers. Some powders, such as dry mustard and cayenne can also act as emulsifiers but aren’t as effective as chemical emulsifiers. Emulsifiers act as the glue that holds the oil and water together, forming a stable sauce. They contain molecules that can bond with both oil and water and act to coat the oil droplets to prevent them from forming a single, oil mass.
To make an emulsified sauce, like hollandaise, the oil product (in this case, butter) is added to a mixture of water and an emulsifier in a quick, whisking action. When the oil is added to the mixture it is broken up into tiny droplets, but immediately coated with by the emulsifier yielding a smooth, consistent product. Enter the trick with creating a successful emulsion for hollandaise: the temperature. Emulsion sauces all contain proteins. If the proteins become too hot, they will coagulate or change from a liquid into a semi-solid ingredient. In the case of hollandaise, the temperature must be watched closely. It must be hot enough to melt the butter, but not so hot that it coagulates the eggs, which can lead to the creation of scrambled eggs within the sauce; not exactly the desired outcome or a perfect hollandaise.
An alternative explanation of how the process of emulsion works is that the emulsifiers change the inward pull, or surface tension, of one of the liquids in the emulsion. The liquid loses its inward pull resulting in it becoming juicy, allowing it to run between the droplets of the other liquid, thus forming a smooth bond. An example of this is the process of making mayonnaise; another popular emulsion sauce. In the case of mayonnaise made with whole eggs, most of the liquid comes from the egg whites. The emulsifiers within the egg yolks dissolve in the egg whites and drastically lower its surface tension. Oil is added while the liquid ingredients are whisked together vigorously and the oil is broken into tiny droplets. The egg yolks coat the droplets and water with a very low surface tension allowing the water to flow easily between the oil droplets, paving the way to a good, smooth mayonnaise.
Additional, popular emulsion sauces include: béarnaise sauce, vinaigrettes, maltaise and mousseline (sauces spawned from hollandaise), Caesar dressing and emulsified French dressing.
At the end of day four of Culinary Skills II, my hollandaise was a success. I was even shown and experimented with how to break up the smooth emulsion of the sauce and bring it back together. As a recap of creating a successful emulsion sauce: a) start with a thick base, this will help make the sauce thicker; b) use a good emulsifier, emulsifiers coats the droplets of one of the liquids to prevent it from running together with the other liquids; c) whisk liquids rapidly as the oil or butter is added, this helps break up the liquid into tiny droplets that can be surrounded by the emulsifier; d) make sure there is enough liquid to surround the droplets, there must be enough or the droplets will be forced together and create one oil mass; e) keep an eye on the temperature, proteins need heat to unwind, but too much heat can cause them to coagulate and make scrambled eggs out of your hollandaise.
(Sources: Cookwise, The Hows & Whys of Successful Cooking with over 230 Great-Tasting Recipes by Shirley O. Corriher, Professional Cooking, Sixth Edition by Wayne Gisslen, On Food and Cooking, The Science and Lore of The Kitchen by Harold McGee.)