Emulsions: Better Cooking Through Science 01

[Hiroyuki]

Emulsification is required to prevent chahan (stir-fried rice) from becoming greasy, as suggested here in the Japan Forum.

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So how are the components (egg, oil, rice) of this emulsion interacting?

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Moisture on the surface of each grain of rice, runny egg, and oil interact with one another to make thin coating on the surface of each grain of rice. The egg has to be runny and be stirred with rice quickly enough, before it is set. Otherwise, the resulting chahan will get greasy.

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So each grain of rice is coated with an emulsion of water, egg and oil. Is that the idea?

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Exactly. I once saw two photos of rice grains somewhere on the Internet, one showing a grain coated with an emulsion (good example) and the other showing a grain coated with oil (bad). I tried to find them but I couldn't.

So, I suppose there are different levels of emulsification.

[qrn]

[

 

Great. Where might one find lecithin locally?

[

I got it from a Whole Foods type market , Its a "natural food suppliment"

Probably a health food store would have it as well..It was $6 0r$7 for a half pound...I bought it to use as a part of a dough improver for bread..so this is just an additional usage...Its called soy lecithin granules..

Bud

[ChefJB]

To answer the question about the act of finishing a sauce with butter or a buerre blanc Buerre fondue etc..... the reason that these work is due to the fact that butter is an emulsion to begin with.

*edited for spelling*

Edited December 11, 2006 by ChefJB (log)

[Chris Amirault]

OK, but why does that emulsion create an emulsion with the rest of the sauce ingredients?

[ChefJB]

OK, but why does that emulsion create an emulsion with the rest of the sauce ingredients?

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You are not necissarily creating a new emulsion, by gently working the butter in you are allowing the already present emulsion(butter) to have more of the water(figurativley speaking) phase added to it thereby changing the flavor and consistency. That is why you use cold butter to make buerre blanc, melted butter doesnt emulsify as well besause the emulsion is already broken. I hope I am making sense, My copy of On Cooking is in my desk at work, I usually refer to Harold as he has such a nice way of explaining this.

[ChefCrash]

[

Great. Where might one find lecithin locally?

[

I got it from a Whole Foods type market , Its a "natural food suppliment"

Probably a health food store would have it as well..It was $6 0r$7 for a half pound...I bought it to use as a part of a dough improver for bread..so this is just an additional usage...Its called  soy lecithin granules..

Bud

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Thanks qrn.

[ChefCrash]

What a coinkidink, I just watched a forgotten recorded 'Good Eats' episode titled "The case for butter". Alton says that butter contains lecithin.

Does that answer your question Chris?

[Chris Amirault]

That and the point about cold butter, which I've known as a technique but never understood.

Anyone make any headway on that list of emulsifiers?

[scott123]

For instance, is an ingredient's ability to emulsify quantifiable, and, if so, what are the units involved?

Is water activity tied to emulsification? Viscosity? Is that what makes sugar an emulsifier?

Arrange the following list in order of emulsifying ability (from strongest to weakest):

...

If a list like this existed (I know it doesn't) it would be immeasurably helpful to me- helpful on a daily basis, not just the two times a year I make mayo.

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Those all seem like really good questions to me. Is there any way to find out the answers? I'm snooping around to find out, but, honestly, I don't have the information at hand.

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Anyone make any headway on that list of emulsifiers?

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As much as I appreciate the thought/effort and would LOVE to find an answer to my question(s), I'm not really expecting an answer. It was more of a rhetorical rant than a quest for info.

I think my problem lies in two areas:

1. Industrial emulsifiers (such as mono and diglyercides and, to an extent, lecithin) have manufacturers that, in order to get companies to use them, publish reams and reams of technical info.

2. Mayo is novel/cool and a great introduction to emulsification.

Weak emulsifiers don't get a lot of press. Flour companies don't have a lot of impetus to market their product as an emulsifier/publish info on it, nor is flour emulsification sexy enough for Alton or Harold to talk about. It falls through the cracks, and, in the process, ends up being a pretty big hole in culinary wisdom, imo.

[Chris Amirault]

Well, that sounds to me like a call to action. What might we all be able to rig up to get a sense of, say, flour's emulsifying powers?

[snowangel]

For a moment, let's leave flour in the dust, and think about my current question. For potstickers, I make a garlic/soy/sesame oil dipping sauce.

How do I keep it emulsified? The garlic is better not pureed, but I want t avoide the dreaded Oil Slick on the top. ???

[slkinsey]

I thought I'd add info to the pile with some stuff I wrote back in aught-five in response to a discussion having to do with emulsifiers. . .

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Many people misunderstand what an emulsion is. For example, I recall hearing of a deviled egg recipe in which the cooks described the hard-cooked yolk puree as being "emulsified with duck fat." People also sometimes speak of things like béchamel as being an "emulsion." This is a misunderstanding of emulsification.

What is an emulsion? An emulsion is a mixture of two immiscible liquids.* If you ain't got two immiscible liquids, you ain't got an emulsion.

But that's not all. An emulsion combines the two immiscible liquids such that one liquid is colloidally dispersed in the other. These are called the dispersed phase and the continuous phase, respectively. In emulsions, the main stabilizing force is electrostatic stabilization, which is is based on the mutual repulsion of like electrical charges.

An emulsifier is simply something that stabilizes an emulsion.

Looking at the example of béchamel, it would be incorrect to think of this as an emulsion. I don't think starch emulsifies the fat and water so much as it thickens the whole deal. It would not be correct, I think, to describe a béchamel as "a fat phase colloidally dispersed in a water phase" because that substantially misses the point.

An emulsion is, by definition, a kind of colloid. In a colloid small droplets or particles of one substance, generally between one nanometer and one micrometer in size, are dispersed in another substance. Milk is already a colloid. So is cream. So is butter. In fact, these are all emulsions -- colloidal dispersions of one liquid phase inside of another.

Where does this bring us with respect to starch-thickened sauces like bechamel? Well, we said it right there: starch thickened. It's not like we can add a tiny bit of starch to butter and milk and voila! an emulsion. In fact, we don't need to use starch at all. Toss some milk and butter into a homogenizer and you'll end up with cream. Perfectly stable as long as the relationship between the fat (dispersed phase) and water (continuous phase) remains within the proper tolerances. With a starch thickened sauce, rather, it is the starch that does the thickening. The sauce doesn't become thick, homogenous and stable unless enough starch is added. I wouldn't describe bechamel as "fat (butter) dispersed in water (milk) and stabilized by starch." What we have in bechamel is a solid phase (the starch granules) dispersed within a liquid phase (water) with some other stuff in the game (fat, salt, nutmeg, etc.). This is known as a sol, not an emulsion. Bechamel is thus related to paint rather than mayonnaise in the colloidal sense.

* When classifying colloids we have the following dispersed/continuous phases: gas/liquid = foam; gas/solid = solid foam; liquid/gas = liquid aerosol; liquid/liquid = emulsion; liquid/solid = gel; solid/gas = solid aerosol; solid/liquid = sol; solid/solid = solid sol. There is no gas/gas colloid, because gasses are mutually soluble.

[snowangel]

So Sam, how do I avoid the Oil Slick in the garlic/soy dip? No flour, please!

[MelissaH]

So Sam, how do I avoid the Oil Slick in the garlic/soy dip?  No flour, please!

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Have you tried mechanical emulsification? Put the soy and sesame oil in a blender or food processor, or go after it with a blender-on-a-stick, and beat the bejeezus out of it? Then, since you'd prefer not to have pureed garlic, add that afterwards? It might hold for a little while.

MelissaH

[slkinsey]

Well, you can use some kind of emulsifier to stabilize it. But you're going to get some thickening if you do, and it will go opaque. It'll become like a garlic/soy/oil mayonnaise. There's no way around that. If you want it to have the lighter, more runny texture of a salad dressing, there's no way it'll stay mixed for more than a short period. It is the nature of this kind of dressing (just like oil/vinegar salad dressing) that it separates after a while. Nothing to be done about it except to stir the bowl of dipping sauce before you dip. FWIW, separation seems to be fairly traditional. I don't recall seeing a dumpling sauce that stayed mixed. On the other hand, you may simply be using too much sesame oil. It's so strong, I don't see any need to use so much that it would even make an oil slick. A few drops on the surface will generally suffice, and this seems standard.

What about adding a little bit of something like peanut butter or sesame paste? Then, if you whizz the whole thing around for a while in a blender or miniprep, it ought to stay mixed for quite some time.

[scott123]

I thought I'd add info to the pile with some stuff I wrote back in aught-five in response to a discussion having to do with emulsifiers. . .

* * *

Many people misunderstand what an emulsion is.  For example, I recall hearing of a deviled egg recipe in which the cooks described the hard-cooked yolk puree as being "emulsified with duck fat."  People also sometimes speak of things like béchamel as being an "emulsion."  This is a misunderstanding of emulsification.

What is an emulsion?  An emulsion is a mixture of two immiscible liquids.*  If you ain't got two immiscible liquids, you ain't got an emulsion.

But that's not all.  An emulsion combines the two immiscible liquids such that one liquid is colloidally dispersed in the other.  These are called the dispersed phase and the continuous phase, respectively.  In emulsions, the main stabilizing force is electrostatic stabilization, which is is based on the mutual repulsion of like electrical charges.

An emulsifier is simply something that stabilizes an emulsion.

Looking at the example of béchamel, it would be incorrect to think of this as an emulsion.  I don't think starch emulsifies the fat and water so much as it thickens the whole deal.  It would not be correct, I think, to describe a béchamel as "a fat phase colloidally dispersed in a water phase" because that substantially misses the point.

An emulsion is, by definition, a kind of colloid. In a colloid small droplets or particles of one substance, generally between one nanometer and one micrometer in size, are dispersed in another substance. Milk is already a colloid. So is cream. So is butter. In fact, these are all emulsions -- colloidal dispersions of one liquid phase inside of another.

Where does this bring us with respect to starch-thickened sauces like bechamel? Well, we said it right there: starch thickened. It's not like we can add a tiny bit of starch to butter and milk and voila! an emulsion. In fact, we don't need to use starch at all. Toss some milk and butter into a homogenizer and you'll end up with cream. Perfectly stable as long as the relationship between the fat (dispersed phase) and water (continuous phase) remains within the proper tolerances. With a starch thickened sauce, rather, it is the starch that does the thickening. The sauce doesn't become thick, homogenous and stable unless enough starch is added. I wouldn't describe bechamel as "fat (butter) dispersed in water (milk) and stabilized by starch." What we have in bechamel is a solid phase (the starch granules) dispersed within a liquid phase (water) with some other stuff in the game (fat, salt, nutmeg, etc.). This is known as a sol, not an emulsion. Bechamel is thus related to paint rather than mayonnaise in the colloidal sense.

*  When classifying colloids we have the following dispersed/continuous phases: gas/liquid = foam; gas/solid = solid foam; liquid/gas = liquid aerosol; liquid/liquid = emulsion; liquid/solid = gel; solid/gas = solid aerosol; solid/liquid = sol; solid/solid = solid sol.  There is no gas/gas colloid, because gasses are mutually soluble.

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In what way is béchamel not an emulsion? Milk and butter are immiscible. Without flour, you've got a pool of melted butter floating on the top of milk. When flour is added, the butter becomes miscible. The result? A continuous water phase surrounding tiny droplets of milkfat (an oil-in-water emulsion).

Is this electrostatic stabilization? Probably not. Does it have to be electrostatic stabilization in order for flour to be considered an emulsifier or for béchamel to be considered an emulsion? No, it does not.

From the Encyclopædia Britannica (bold mine):

emulsion

Mixture of two or more liquids in which one is dispersed in the other as microscopic or ultramicroscopic droplets (see colloid).

Emulsions are stabilized by agents (emulsifiers) that (e.g., in the case of soap or detergent molecules) form films at the droplets' surface or (e.g., in the case of colloidal carbon, bentonite clay, proteins, or carbohydrate polymers) impart mechanical stability. Less-stable emulsions eventually separate spontaneously into two liquid layers; more-stable ones can be destroyed by inactivating the emulsifier, by freezing, or by heating. Polymerization reactions are often carried out in emulsions. Many familiar and industrial products are oil-in-water (o/w) or water-in-oil (w/o) emulsions: milk (o/w), butter (w/o), latex paints (o/w), floor and glass waxes (o/w), and many cosmetic and personal-care preparations and medications (either type).

From Wikipedia (bold mine):

An emulsifier (also known as an emulgent or surfactant) is a substance which stabilizes an emulsion. Examples of food emulsifiers are egg yolk (where the main emulsifying chemical is the phospholipid lecithin), and mustard, where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers; proteins and low-molecular weight emulsifiers are common as well. In some cases, particles can stabilize emulsions as well through a mechanism called Pickering stabilization.

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Emulsifiers need not be electrostatic. They need not be phospholipids. They can be mechanical/particulate in nature. The last time I checked, bentonite clay was not a phospholipid. That molecule ain't got no tail.

The definition of an emulsion may not be as narrow as you perceive it to be. I'm sure there's quite a few people in the 'emulsification has to be electrostatic' camp, but I'm not one of them. And, by the looks of these two links, I'm not alone.

[scott123]

For a moment, let's leave flour in the dust, and think about my current question.  For potstickers, I make a garlic/soy/sesame oil dipping sauce.

How do I keep it emulsified?  The garlic is better not pureed, but I want t avoide the dreaded Oil Slick on the top.  ???

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Gelatin is a weak emulsifier, but loses gelling power in salty environments. If you've got some xanthan gum, that might help.

Is the sauce cooked? I'd probably just go with either an arrowroot or a cornstarch slurry. It shouldn't take much.

[Chris Amirault]

So here's a question. Mashed garlic clove with anchovy paste, black pepper, and mustard. Whisked in a little homemade worcestershire sauce, then a little cider vinegar. A drop of olive oil at a time, whisking hard... and it never emulsified.

Thoughts?

[qrn]

So here's a question. Mashed garlic clove with anchovy paste, black pepper, and mustard. Whisked in a little homemade worcestershire sauce, then a little cider vinegar. A drop of olive oil at a time, whisking hard... and it never emulsified.

Thoughts?

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try the lecithin as I did in this post up thread HERE

Its not a permananent thing but works well for s/d..

Bud

[Reefpimp]

Two thoughts occur to me:

One, a liquid surrounded by another liquid forms a sphere (surface tension equalizing in all directions, I'd guess). Not a lot of opportunity for mechanical bonding on a spherical surface.

B) Given that emulsification and consistency are closely related but are in fact two separate things, are there emulsifying agents and thickening agents that are incompatible with each other and combinations to be avoided?

[ChefCrash]

So here's a question. Mashed garlic clove with anchovy paste, black pepper, and mustard. Whisked in a little homemade worcestershire sauce, then a little cider vinegar. A drop of olive oil at a time, whisking hard... and it never emulsified.

Thoughts?

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I just happened to be reading about making clarified butter here,

I found this post:

In laboratory separations, I often find it helpful to add NaCl to the aqueous layer to increase polarity; it helps reduce an emulsion at the interface between two layers. By this token, using salted butter should hasten the separating process.

Could it be that, excessive amounts of salt from the anchovies/Worcestershire as well as additional salt you may have added, have been the culprits?

[C. sapidus]

In laboratory separations, I often find it helpful to add NaCl to the aqueous layer to increase polarity; it helps reduce an emulsion at the interface between two layers. By this token, using salted butter should hasten the separating process.

Could it be that, excessive amounts of salt from the anchovies/Worcestershire as well as additional salt you may have added, have been the culprits?

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Yes, I would guess that the salt was the culprit, and the anchovy paste is probably the saltiest ingredient that you used. For an interesting experiment:

1. Make the same mixture without the anchovy paste. Does it emulsify?

2. Add the anchovy paste at the end and see if it breaks the emulsion.

3. If the emulsion breaks, add lecithin or another emulsifier and see if you can re-emulsify the mixture.

C'mon, Chris, do it for science!

[Dave Hatfield]

So here's a question. Mashed garlic clove with anchovy paste, black pepper, and mustard. Whisked in a little homemade worcestershire sauce, then a little cider vinegar. A drop of olive oil at a time, whisking hard... and it never emulsified.

Thoughts?

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Where's the emulsifier in that lot? Sounds like you were half way to a Caesar salad dressing.

In fact last night I did make a Caesar salad & the dressing emulsified with no problem.

2 egg yolks + lemon juice + dry mustard + Worcestershire sauce

+ Pinch salt + Pepper. Whiz in food processor.

Dribble in olive oil voilà mayonnaise. add garlic- add anchovies - add parmigiana.

Still nicely emulsified. In fact the cheese seemed to thicken it ever more.

Now have a nice Caesar salad dressing.

Later, since I'd made too much I tried a totally unscientific experiment.

First I added at least two tablespoons of Worcestershire sauce - slowly. It still held.

Next I started adding more anchovies - one fillet at a time (these were salt & oil packed). It still held. Give up after five fillets.

By now the dressing was inedible, BUT it was still an emulsion. GO figure?

Don't know that I've really added anything useful to the discussion, but I can say that before experimentation it was a really nice way to make a Caesar salad dressing. It tasted great & coated the lettuce very nicely.

[Chris Amirault]

You may have added something: you introduced the salty anchovies after the emulsion was formed, not before, as I did.

[qrn]

You may have added something: you introduced the salty anchovies after the emulsion was formed, not before, as I did.

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But he had 2 egg yolks...

Bud