Roux the day....

[evenstranger]

I've been making roux for years to thicken and provide a base for soups, sauces, etc. Yesterday, I skipped the roux. The soup I was working on was not thickening up like I would like (potato soup, was hoping the potato starch would thicken more). I remembered someone telling me I could use a flour and liquid slurry to thicken it. I've done this before with cornstarch, and apart from a cornstarch flavor, it worked pretty well. So I tried it with flour, milk and some sour cream, since I was going to add it in anyway. The soup thickened up immediately, now almost too thick.

So here's my question - should I have started with a roux, or was this the better approach. I'm thinking thickening at the end is better so that the other ingredients have plenty of liquid to cook, meld and concentrate as the liquid reduces.

Thanks!

 

[evenstranger]

By the way, the soup was very good... I'll gather my notes and post the recipie.

 

[jabbur]

I've made soup both ways. I never really noticed a difference in taste. Usually I'll add the slurry for soups that need sauteed veggies. That way, I cook the veggies in the butter, add the broth and seasonings and heat it up and at the last add the slurry to thicken it. If it thickens too much, I add more broth or cream until I get the consistency I want.

 

[csalt]

You could try whisking a small amount of semolina in at the end, or else add some pearl barley mix while it is cooking.

 

[Andy M.]

The benefit of a roux over a slurry is that you can make a roux darker. Cooking the roux for longer will cause the color to darken, changing the flavor at the same time. If you always make a white or blonde roux, there is no real difference vs. making a slurry other than the added fat in the roux. Be sure to cook the soup or any dish for a few inutes after adding a slurry to ensure the raw flour taste is gone.

You could puree some if the potato in the soup as a thickener.

 

[csalt]

In my ignorance I have only ever heard the UK definition of 'slurry'
slurry
so my neck hairs tend to stand on end when I read it in connection with cooking

 

[Mirandgl]

I have a great many soups and sauces that I thicken with a roux at “the End”. The roux should be added to the liquid in small batches and beaten vigorously to prevent lumping. This may not work if you want a chunky potato soup.

The flour and water method you used is known as Whitewash. It does not have the flavor or texture you can get from a roux but if your soup had a good seasoning it seemed to be acceptable to you.

Cornstarch allows for a clear sauce and I don’t have a problem with the flavor. Arrowroot is use like cornstarch and will provide an even clearer sauce but is expensive.

There are some other thickening agents you can use. I have used bread crumbs on occasion when texture was not an issue but they will thicken a liquid very quickly so moderation is advisable.

 

[Charleysaunt]

The advantage of a roux is that the flour is cooked, whereas with the slurry it is still pretty "raw", but the soup flavor probably took care of what little there might be. And of course, for a potato soup you would not want a darker roux, as you might for gravy. Nor a gumbo roux, which is not for thickening at all, but for flavor.
For thickening a potato soup, you could either take out a potato and whiz it up in the FP, or add instant potato flakes.
Bean soups, for example, can be thickened by removing some of the cooked beans and blending them and adding back.