# Why does Cornflour split a sauce/soup?



## soubise (Feb 12, 2013)

Cornstarch for you Americans.

I've found a starch thickened sauce or soup kept in a bain marie for a long sometimes splits.

This usually happens when its been there for a few hours or longer. Not supposed to keep them there for longer than 4 hours but our bain marie's at work are on all day and get changed halfway through service which is about 5 hours each way. 

It usually happens with leek and potato and mushroom soup, say if its been made without a roux and the cornflour was added just to adjust the consistency of the potato soup. We sometimes use a starch thickened white sauce which can split as well.

Just made me wonder if anyone else had discovered this before


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## michaelga (Jan 30, 2012)

Yup - cornstarch will breakdown and loose it's thickening ability if held for a long time at serving temp. It is also less stable under refrigeration.

Here is a post from this site about it from 2005 - probably earlier ones also to be found.

http://www.cheftalk.com/t/15684/flour-vs-cornstarch

I didn't think it was such an obscure bit of knowledge.

One funny thing to do is give the broken gravy or sauce to a junior guy and ask him to thicken it up again.

(something about the way it breaks down prevents it from coming together again... no mater how much roux or cornstarch you add... some kind of enzyme thing... funny as all hell watching the new guy whisk and whisk and whisk more starch into the gravy)


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## lagom (Sep 5, 2012)

Cornstarch also adds a texture to soups and sauses that I at least find unpleasant in the mouth feel. I would recomend not using it for the most part. However I do know that here in Sweden people use it with wanton abandon, thus the reason finding a decent soup here is so hard, not to mention the wine sauses. I dont think a lot of cooks here believe in reduction.


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## junglist (Jul 13, 2010)

My chef and I just had a brief conversation about corn starch. At our place we prepare a garnish of crispy shallots, and learning the recipe I noticed corn starch was an ingredient. Tasting the end result I noticed the shallots were really dense, and I asked why corn starch was in the recipe? Unfortunately it wasn't his decision; next time I made a small batch without the stuff and had everyone try them, and they said they were the crispiest shallots they've had there.

Another place I used to work at had honey-glazed carrots on their menu, with... corn starch! My manager and I took one look at the recipe and changed it then and there.

I kind of agree people rely on it way too much, when a little time and patience can remedy what corn starch is usually used for, but to each his/her own. I used to work at a place where they used it to fix _everything_.


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## adamburgerdavis (Apr 2, 2012)

I'm going to have to agree with Lagom and Junglist here. If you take corn starch and slurry it into just plain chicken stock and then taste it for texture the mouth feel is unbearable. I've seen people use it for frying and it work okay sometimes but all you need to do is have the right temperature oil and not to overcrowd or bring the temp down when adding whatever you're frying and it becomes unnecessary.


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