Tuesday, July 15, 2008

Emulsions 101: No Yolk Required

I'm posting the photos below by way of addressing a misconception about emulsified sauces that I believe is in part a function of the use of emulsions made with egg to explain how emulsions are made and structured. Because emulsified sauces like mayonnaise and hollandaise sauce are widely known to depend on the presence of the emulsifying agent lecithin in egg yolk to enhance the attraction of fat and water in the ingredients, many cooks assume that in order to create any emulsion lecithin or some other emulsifying agent, must be added to any recipe that one wants to emulsify. Not so.

Given the right tools an emulsified "sauce" can be made with nothing more than water and an off the supermarket shelf vegetable oil. Take a typical oil in water emulsion as an example.

In a simple oil in water emulsion the oil is broken up into millions of tiny drops that are suspended in a continuous sheet of water. As long the oil is a pure oil made up of only one type of very hydrophobic (water repelling) oil molecule, the likelihood of making the oil and water attractive to each is very low. However, culinary oils are never entirely pure. They always contain more than one type of oil molecule some more hydrophilic (attractive to water) than others. They also contain a certain amount of protein and other "impurities" that can be quite attractive to water under the right conditions.

And what are those conditions?

Well, first and foremost the temperature needs to be within a certain range. The range will vary slightly from oil to oil, but generally it should be between 60-80 degrees F. Room temperature if you will. (The water needs to be about the same temperature too.) Next, the oil must be broken up into the smallest droplets possible so that a maximum of surface area of the oil is exposed to the water.

The best commonly available tool for breaking up the oil into droplets is an immersion blender. A standard blender is almost as good, but cannot match the efficiency of a device that enables you to raise and lower the spinning blade. I've made emulsions with nothing more than cool water and high quality cold pressed and minimally filtered olive oil and an immersion blender.

The photos below show an emulsion that I made today from balsamic vinegar, olive oil and garlic. I added the garlic after the emulsion came together, so it played no role in enhancing the attraction of the oil and the water.






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5 comments:

Scotty said...

I completely agree with what you state, Bob, but I think that one must be wary of "over-emulsifying" whatever you are blending electronically. I have seen emulsified vinaigrettes go from the "emulsified so it doesn't break" to library paste in a fairly brief time.

Part is the balance of ingredients. Part is what to look for. I can eyeball it, but I don't know how to explain what I am seeing.

Any thoughts?

Bob del Grosso said...

Scotty
I'm not entirely sure about what you are asking but I will say this.

If you are referring to low temperature oil in water emulsified sauces then library paste is a very good thing. At that viscosity you have a tremendous attraction between the two phases of the emulsion and a very stable sauce that only needs a bit more water (e.g. vinegar) to bring it to the correct consistency for service.

drago said...

What ratio of oil:vinegar are you using for a sauce of that consistency?

Bob del Grosso said...

Drago

The ratio is 1:1. Balsamic vinegar is so sweet that I find I need to use a lot more to get the right level of acidity. The standard 3:1 of oil to vinegar does not work for me.

Bob del Grosso said...

Drago

I should add that the consistency is more a function of the superior nature of the emulsion as produced by the immersion blender than the ratio of oil to vinegar.