Oil Separation in Gumbos, Curries

[Chris Amirault]

Back in the gumbo cook-off, we've been wondering why oil separates out of a roux to the surface of the gumbo. (Click here for the most recent part of that discussion.) A few people have noted that this occurs with curries, chili, and other dishes. I'm stumped. Any ideas?

[snowangel]

Linda and I have pondered this. In the first batch of gumbo I made, there was no separation. Yesterdays had minimal separation (less than 1/4 cup of oil, and some of that could have come from the sausage or chicken). Linda reported recently that almost all of the oil in a gumbo separated out.

I don't notice that much separation when I make a coconut milk based curry.

What's interesting is that when I make a roux with butter, there is no separation. Suppose the dairy component acts as a binder?

[sanrensho]

I don't notice that much separation when I make a coconut milk based curry.

In the case of Thai coconut milk curries, the coconut milk is purposely boiled until the oil separates. (To my understanding, this is seen as desirable to the presentation of Thai coconut milk curries.) This process takes about 5-10 minutes.

[JayBassin]

If you add hot stock to a hot roux, it will separate. You need to add cold or room-temp stock to the hot roux, whisking in.

[miladyinsanity]

I don't notice that much separation when I make a coconut milk based curry.

In the case of Thai coconut milk curries, the coconut milk is purposely boiled until the oil separates. (To my understanding, this is seen as desirable to the presentation of Thai coconut milk curries.) This process takes about 5-10 minutes.

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That's right, and to my knowledge, applies to certain Indian and Malay curries as well. It looks better with the oil, apparently. I guess that's because it's not good for you.

Susan, not all coconut curries will separate that much. My mom's chicken curry, made with coconut milk, doesn't either.

[sanrensho]

My mom's chicken curry, made with coconut milk, doesn't either.

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Is that because of the preparation? I'm assuming that you could make any coconut curry separate by boiling the milk sufficiently.

[miladyinsanity]

Good question. I don't know. Mind, this was before she switched to using cow's milk for it because it's healthier. It's been awhile since she last used coconut milk for curries.

But if it helps, I do know my aunt's maid used to make coconut oil herself by keeping coconut milk over night in the fridge, before boiling it until it separated.

[Shalmanese]

The lecithin in the butter is an emulsifier as is, I suspect a couple of other things that would typically go into gumbos/curries. I suspect a large part of seperation has to do with the mechanics of how you are making a dish. Perhaps if there is already a large oil slick on top of the soup, it can act as a "seed stock" for smaller oil droplets to attach onto which would increase the rate of seperation.

[Adam Balic]

Small drops of oil held in an aqueous suspension by various mechanisms (proteins like lecithin), If you heat the system enough these tiny droplets fall apart (e.g. for example the lecithin is denatured by the heat) and the tiny oil blobs fuse until they form a droplet big enough to see with the naked eye. Whole cows milk will do this if you heat it enough, but it has less fat then coconut milk so the effect may not be as obvious.

Roux is like the base for bechamel and veloute sauces? I always add hot milk/stock for these and I have never had an isue with them seperating.

[Corinna Dunne]

Roux is like the base for bechamel and veloute sauces? I always add hot milk/stock for these and I have never had an isue with them seperating.

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Me too... in fact I prefer this way because you are less likely to get lumps when the liquid you add is hot.

[mrbigjas]

Roux is like the base for bechamel and veloute sauces? I always add hot milk/stock for these and I have never had an isue with them seperating.

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yes it is.

and after extensive experimentation* i haven't found that the hot/cold debate has any merit on either side. hot or cold works fine as long as you whisk it in well.

*meaning sometimes i remember to heat the liquid, and sometimes i don't.

[Chris Amirault]

Two questions:

The lecithin in the butter is an emulsifier as is, I suspect a couple of other things that would typically go into gumbos/curries. I suspect a large part of seperation has to do with the mechanics of how you are making a dish. Perhaps if there is already a large oil slick on top of the soup, it can act as a "seed stock" for smaller oil droplets to attach onto which would increase the rate of seperation.

←

So, based on that, one can reduce separation with an emulsifier such as lecithin. Is gumbo file (sassafras) an emulsifier? Are there others that we should be thinking about in this discussion?

Also, Shalmanese's comment and Adam's below --

Small drops of oil held in an aqueous suspension by various mechanisms (proteins like lecithin), If you heat the system enough these tiny droplets fall apart (e.g. for example the lecithin is denatured by the heat) and the tiny oil blobs fuse until they form a droplet big enough to see with the naked eye. Whole cows milk will do this if you heat it enough, but it has less fat then coconut milk so the effect may not be as obvious.

←

-- would suggest that frequent stirring at lower temperatures is preferable to letting your gumbo/curry/chili sit to boil at higher temperatures. Is this why the homespun advice about cooler stocks seems relevant? If you whisk in cooler stocks into these bases (roux, bhunoed whatever), then you're lowering the temperature both by the addition and the whisking.

[miladyinsanity]

Also, Shalmanese's comment and Adam's below --

Small drops of oil held in an aqueous suspension by various mechanisms (proteins like lecithin), If you heat the system enough these tiny droplets fall apart (e.g. for example the lecithin is denatured by the heat) and the tiny oil blobs fuse until they form a droplet big enough to see with the naked eye. Whole cows milk will do this if you heat it enough, but it has less fat then coconut milk so the effect may not be as obvious.

←

-- would suggest that frequent stirring at lower temperatures is preferable to letting your gumbo/curry/chili sit to boil at higher temperatures. Is this why the homespun advice about cooler stocks seems relevant? If you whisk in cooler stocks into these bases (roux, bhunoed whatever), then you're lowering the temperature both by the addition and the whisking.

←

In this case, with regards to coconut milk curries, it'd be started off by the oil used to sautee the spices and onions and garlic, wouldn't it?

Also, Chris, bear in mind that coconut milk curries are supposed to have that thick film of oil. I'm not sure that it won't taste about the same without it, though. It'd certainly make me feel less guilty about the oil I'm pouring down my throat.

[fifi]

OK . . . As an inveterate gumbo maker I have often been perplexed by the oil break out. I have tried to relate it to the temperature of the stock addition, the amount of gelatin in the stock, any number of things and none of it connects. For any instance that seems to support a theory, there is always an exception. I have searched the usual suspects (McGee et al) and haven't found anything that sheds any light on the issue.

When it comes to oil break out from coconut milk, that is pretty predictable. The same thing happens with cream in a gratin. Predictable. The oil break out in a flour and oil roux with a gumbo is not predictable in my experience.

[Adam Balic]

Two questions:

The lecithin in the butter is an emulsifier as is, I suspect a couple of other things that would typically go into gumbos/curries. I suspect a large part of seperation has to do with the mechanics of how you are making a dish. Perhaps if there is already a large oil slick on top of the soup, it can act as a "seed stock" for smaller oil droplets to attach onto which would increase the rate of seperation.

←

So, based on that, one can reduce separation with an emulsifier such as lecithin. Is gumbo file (sassafras) an emulsifier? Are there others that we should be thinking about in this discussion?

Also, Shalmanese's comment and Adam's below --

Small drops of oil held in an aqueous suspension by various mechanisms (proteins like lecithin), If you heat the system enough these tiny droplets fall apart (e.g. for example the lecithin is denatured by the heat) and the tiny oil blobs fuse until they form a droplet big enough to see with the naked eye. Whole cows milk will do this if you heat it enough, but it has less fat then coconut milk so the effect may not be as obvious.

←

-- would suggest that frequent stirring at lower temperatures is preferable to letting your gumbo/curry/chili sit to boil at higher temperatures. Is this why the homespun advice about cooler stocks seems relevant? If you whisk in cooler stocks into these bases (roux, bhunoed whatever), then you're lowering the temperature both by the addition and the whisking.

←

I have no experience of gumbo, so can't comment, but all the advise I had seen about roux based sauces has been to add warm stock/milk (to decrease lumps) and to simmer (relatively high temperature then) for a long period to allow the starch grains to burst and give a smooth sauce.

With things like curry and gumbo, you might want a lower temperature to prevent the meat from drying out.

[eje]

I never do a really through job of defatting my chicken stock when I make a gumbo, so I always assume floating fat has something to do with that.

I know the darker you cook a roux, the less thickening power it has. Perhaps it also loses some of its power to bind fats into solution (or whatever the correct terminology is)?

fix spelling.

Edited December 15, 2005 by eje (log)

[fifi]

Well . . . All of the normal assumptions about the rules of the road don't seem to work all the time with gumbo. One would assume that the darker the roux the less the thickening power. Yet my seafood gumbo above with a much lighter roux was not as thick as it should have been. I even added less stock than my typical 6 cups liquid to a 1 cup:1 cup roux.

Emulsification issues should react the same, yes? Not really. I have had oil break out, or not, with the really dark, Upperline type. The same with lighter rouxs. Makes no sense.

I am grasping at straws and will throw in another variable, the protein content of the stock. I most often use chicken or turkey stock and make them pretty much the same way. The gel stiffness when cold is about the same as far as I can tell.

On the simmer, gumbos should simmer gently, not boil. Perhaps a little stronger than when making stock but not much. I only stir ever so often, like if I happen to walk by. The heavy pot and gentle temperature seems to prevent any sticking issues.

[Austin]

With my most recent gumbo, I heeded advice previously found in this forum that suggested that the stock should be at room temp or cooler when added to the roux. I did this for the first time and there was no fat separation at all.

Regarding curries, at least Thai and Burmese curries, fat separation is seen as a good thing. When making coconut milk-based curries, Thais fry the curry paste in hua kati ("head of the coconut milk", ie thick coconut milk) until it smells fragrant and nam man tok meaning that the oil has separated. I think this has to do with releasing the oils in the chilies and other ingredients, as well as in the coconut oil, making the dish much more fragrant.

On the topic of oil, the oiliest food in the world must be Burmese food. A typical Burmese curry has a good 3 cm of oil floating on the top! And they are, to my knowledge, the only people in SE Asia who really use peanut oil. Despite what you may read or hear, peanut oil is a rarity in SE Asia--I've never seen it used or for sale in Thailand.

Austin

[Chris Amirault]

All right, I'm going with very low temperatures as a solution. Takes a lot of anecdotal information into account, I think.

Perhaps we should pass the hat and hire McGee on as a consultant....

[fifi]

With my most recent gumbo, I heeded advice previously found in this forum that suggested that the stock should be at room temp or cooler when added to the roux.  I did this for the first time and there was no fat separation at all.

. . . . .

←

The stock temperature is gaining on me as being something of a factor. When I got the almost 2 cups of oil back, the stock was added pretty warm. Not warm enough to make it hard to incorporate, but warmer than normal, nonetheless. Just for a point of reference, when I have added the stock "hot" and gotten "dog barf," the stock was simmering on the back burner. I just don't remember about the oil break out in that disaster. I was too busy stirring like hell to save the gumbo.

Here is my hat, Chris. Go hire McGee.

[fifi]

BTW . . . Remember that gumbo is different from sauces. I also add hot liquid when making a bechamel et al. It works fine. But I don't think we can compare those sauces to what we are talking about here.

When you add hot liquid to the VERY hot roux (even though you have quenched it with the veggies, it is still very hot) you are guaraaawnteed (Justin Wilson accent) to have a problem that I call dog barf. Yes, you can get it to combine eventually if you work really really hard at it. I think that is where gumbo differs from bechamel and their ilk. The roux is usually much hotter than in a sauce. One of these days I am going to use my new Thermopen toy and see just how hot the dark brown roux really is both before and after quenching.

The oil break out is a different phenomenon as compared to the original combining issue. It occurs after simmering for a long time. The gumbo base is usually simmered for about 2 hours. This is another difference from the usual sauces. The same long simmer occurs with curries and chilis. I am pretty sure that if you simmered the sauces for a long time they would break also.

I guess the real question is why it DOESN'T break sometimes.

[Chris Amirault]

Linda, describe the dog barf phenomenon. How much stock do you add to the roux at a time? I mean, if the roux is 350F or so, adding much less than a cup of stock is going to heat that stock up pronto, right?

[fifi]

The dog barf (lovely term) looks like great blobs of greasy flour floating around in liquid. My ladle is a one cup ladle. The first one goes in and is stirred around and the second one follows quickly. After about the third ladle you can add it a little faster.

[Chris Amirault]

OK, so that goes to the keep-it-cool theory: a full cup whisked in, then another and another, is going to keep the stock/roux mixture from being extremely hot. I assume you add your stock after adding the vegetables, too, Linda -- another way that the roux is cooled a bit.

[fifi]

Yep. That is correct. You add the stock after the vegetables and sausage, if you are using sausage. Adding the stock one ladle after another, stirring in between, does cool it down more.