Who Said Oil and Water Don’t Mix?
There is an old saying that water and oil don’t mix. From a scientific standpoint this is almost always true. The polarity of water makes it repel from other lipid or fatty liquids that are otherwise non-polar. This however is not always the case. Have you ever heard of emulsions? An emulsion is a combination of two liquids that would not ordinarily mix together. Oil and water may be the best example of two liquids that normally do not mesh, but can be made into savory recipes such as mayonnaise and hollandaise sauce.
In an emulsion a liquid, such as oil, is broken into millions of small particles and the other liquid, such as water, then surrounds each one of these water particles. This is essentially the same as a suspension, such as salad dressing. The difference between a suspension and an emulsion is that a suspension will eventually separate and the two liquids have to be re-mixed or suspended. An emulsion on the other hand stays as this oil/water solution. The key factor in making an emulsion is the emulsifier. The emulsifier keeps the droplets of liquid from coming together with one another and then crashing out of the solution.
Let’s take a look at what’s going on at the molecular level…
Emulsifiers are molecules that contain both a polar and non-polar end. The hydrophobic tail of the emulsifier surrounds the oil droplets, thus not allowing the oil to make larger droplets. With this emulsifier coating, the oil droplets bounce off one another instead of sticking together and making larger macro-droplets (oil repels away from the hydrophilic head sticking out of the other oil droplets). The hydrophilic head of the emulsifier is then able to interact with the water droplets, preventing them from combining. The water normally has a strong inward pull or surface tension between the water molecules that keeps them compact and stuck together. When the emulsifier dissolves in the water it impedes this inward pull that allows the individual water droplets to get dispersed throughout the mixture. So as we are looking at an emulsion such as mayonnaise we may think the water and oil have become miscible with one another, but on the molecular level there is some trickery going on. The two compounds give the effect of one solution but are not actually mixed together as one solution. The liquids are rather evenly dispersed and forced to stay close together with the aid of an emulsifier.
Common emulsifiers used in cooking are mustard, honey, and vinegar. But the mac-daddy of all emulsifiers is the egg yolk. The egg yolk is the most widely used emulsifier in the kitchen and for good reason. Egg yolks contain lecithin, which is an excellent emulsifier.
Why Buy Hellman’s (mayonnaise) When Homemade Is SO Much Better
The key to making any good emulsion is first making sure to completely disperse and break-up the oil into tiny droplets. A convenient way of doing this is by using a food processor (although a whisk and a little elbow grease works fine too).
What you will need: 1 egg, 1 tsp NaCl, 1 tsp mustard, ¼ tsp sugar, 2 tbsp lemon, 2 tbsp vinegar, 2 cups vegetable oil
Start by mixing the egg in the food processor until well blended. Next add the NaCl, mustard, sugar, lemon, and vinegar and mix again. Then slowly add your oil while the processor is mixing. The mixture will then appear right before your eyes as one mass of mayonnaise! Changing the type of oil can also give you knew and tasty mayonnaises. For those who like something a little spicy, try using a hot pepper flake olive oil. Or if you’re looking for a new bread dip, using olive oil creates a scrumptious little spread (though you should use high quality olive oil and be careful not to process too long, as olive oil mayo may become bitter).
A Yummy and VERY Lemony Hollandaise Sauce…
What you will need: 3 egg yolks, 60g lemon juice, 113 g butter, ½ tsp NaCl, 1 tbsp H2O
Begin by placing the egg yolks, lemon juice, and water in a double boiler. Melt the butter and then drizzle the butter into the egg yolk mixture, being aware to constantly stir with a metal whisk. The sauce will begin to thicken, at this point remove the sauce from the double boiler and continue to whisk as it cools down. As the sauce cools down add NaCl while whisking.
- McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004. Print.
- Corriher, Shirley O. Cookwise: The Hows and Whys of Successful Cooking. New York: William Morrow, 1997. Print.