Why does the roux separate from my gumbo?

Making a roux has two purposes:

1. Coat the flour granules with fat so they are able to dissolve into the cooking liquid without binding up.
2. Cook the flour to remove the raw cereal flavor.

When the cooked, fat-covered, flour is introduced to boiling liquid the starch granules swell and explode tangling up the cooking liquid. The cooking liquid is thus thickened and delicious.

If your roux is separating then the starch has not gelatinized. Because you saw this problem in the slow cooker and not in a pot I suspect that you are simply not bringing your liquid to a full enough boil to gelatinize your starch.

I have never seen a roux separate out. The roux should dissolve into the cooking liquid. You might check your ratio and make sure that you don't have too much oil in your roux. Variability in measuring your flour might account for why you see this intermittently.

I cook gumbo all the time. I usually cook large gumbo for parties.. 30 quarts or greater at a time. I can tell you from experience exactly what is happening... And one of the answers above is right on. Your roux is not mixing due to a temperature issue.

I ALWAYS use 2 pots when making a gumbo... No matter what kind of gumbo it is. I use a cast iron skillet for the roux and a 30qt stock pot or bigger for the actual gumbo.

When I make the roux, I get the fat/flour mix to a chocolate color before cooling it with the trinity. Once I put the trinity in the roux, i stir and sit the roux for 5 - 10 minutes. It cools.

When I transfer to my stock, the stock has to be very hot... A rapid (roaring) boil. If not, the roux will never mix. The stock has to be hot enough for the flour to mix. The oil opened the flour using heat. If the stock isn't hot enough, the heated, open flour will cool and close on impact with the stock causing it to "separate". Once this happens, the roux is toast. Start spooning!

Make sure the temperature of the stock is very hot. Just because you see a boil doesn't mean anything. You need to stir the stock to make sure the boil isn't just from the bottom center of the pot (where the source of the heat is). Though you may see a boil in the middle, if is most likely from the bottom center and rising to the top (heat rises) leaving the sourounding stock below boiling. STIR. STIR. STIR the stock and make sure you have a RAPID boil around the stock and not just the middle. Once you add the roux, continue to stir making sure you don't let the cooler roux affect areas of the stock. Stirring constantly for 5 minutes of so will make sure you blend the roux with the entire stock as well.

I have also had this happen when using a stove or cookware that I was not familiar with. If you end up with a separated roux, spoon out what you can... Make a new roux and add this new roux back in. If the original roux was a dark roux, if will separate as a sheet and not break into granules that sink or are too small to fish out with a spoon. It will not hurt the gumbo. You basically are left with a stock or soup. Get the old roux out.... Boil that stock high... Add a new roux and go to town with the gumbo, chances are some of the original roux did mix well. Cleaning out what didn't mix and adding a new roux will surprise you how thick and flavorful the gumbo can be.

On a side note, the lighter the roux, the greater the roux will act as a thickening agent. The darker the roux, the less it thickens BUT the more it FLAVORS! I have actually intentionally made two rouxs for the same gumbo.... One for thickness and one for flavor. It's easy to screw up by having too much roux... But once you get used to doing it and learning where the right mix is, it can make for an amazing gumbo.

You might try doing the roux and chicken stock in a separate pan. Make the roux, and when it starts to turn golden (or dark brown - your choice), pour in a cup of stock and whisk continuously while adding. This will make a gravy like substance, to which you can add the rest of the stock to thin out to the correct consistency. There's really no reason to coat the vegetables in roux and the only reason the traditional recipe does so is so that you can get away with one pan.

I usually have this same problem when I make a really big batch of gumbo. I've tried all of the usual stuff: adding cold stock to hot roux, hot stock to cold roux, doing an extra vigorous boil. None of it worked. I've come to believe the adding cold to hot trick is old kitchen lore that has no scientific foundation.

To settle this, I read some academic papers on the subject. My summary is below, but I highly suggest you read this article if you're interested in the subject.

To start, there are three ways to get oil and water to mix together.

1. Vigorous mixing breaks up oil and water into tiny droplets that disperse through each other. Eventually, the droplets will eventually recombine with their like droplets until there's once again oil floating on top of water.
2. Emulsifiers include ingredients like egg yolks and mustard. Emulsifiers are molecules that have one end that is attracted to oil and another end that is attracted to water. When oil and water are mixed together in the presence of an emulsifier, the tiny droplets are held together by the emulsifier. This prevents the droplets from recombining as quickly as in #1. One example of an emulsion is mayonnaise which is oil and vinegar emulsified with an egg yolk.
3. Starches act as a thickening agent and thus get in the way of oil droplets trying to recombine.

Here's what you should do
If your oil is separating out then your roux didn't have enough thickening power. The flour loses its thickening power the longer you cook the roux. To make up for this loss you can add some additional raw flour after your roux has achieved a deep copper brown. This extra flour at the end will retain its thickening power, which will give you some additional insurance in preventing your roux from breaking.

For full disclosure I haven't tried this yet. I'm making gumbo later this week, so I'll try to report back. The paper I linked above has me convinced this will work though. I'll update this post later if I can remember.

I've had my roux separate on more that one occasion and the cause I found was in the technique of adding cold stock to a hot roux, you have to temper your roux with the colder stock a little at a time, or you will end up shocking the oil and flour and the roux will separate from the stock liquid. I found the remedy to this; Oh shet moment on a Cajun cooking website that saved the day, and it was a pretty easy fix, just crank up the heat and continue to stir your gumbo until the stock and roux reach a temperature where they come back together.

Although I am not from Louisiana, I have made gumbo dozens of time and live in the New Orleans area, I had my roux separate twice. Tonight was the second time. I found a fix on another web page. I used Xanthan gum which is an emulsifier. It bonded the roux to the stock. However I used too much and now my gumbo is extra thick. Make a slurry with it first and then add to the gumbo and it will pull it together. It doesn't need much. it may be hard to find though. i found it at a larger grocery store with the gluten free foods and the health food.

You must temper your roux. Hot roux likes cold stock, cold roux likes hot stock.

Not cooked enough. Boil it an additional 15 minutes on the stove top. I always use unbleached all-purpose flour. Good-Luck!

Chef Bourque'