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When I cook this particular sauce in this particular pan it leaves this weird red (slightly purplish) reside that doesn’t wash off with soap but does come out in oil. The ingredients in the sauce are “tomatoes, tomato purée, less than 2% of: salt, basil oregano, parsley, onion powder, garlic powder, citric acid, natural flavors. (Brand is giant foods which is a regional supermarket chain). The pan is a nonstick.

Does anyone know what this residue might be?

Also no idea what the tags should be.

enter image description here

mroll
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    Do other tomato sauces not stain your pan? – Kat Feb 28 '21 at 05:40
  • Can you expand on "does come out in oil"? Also, is that a special ceramic nonstick pan, or regular teflon? – FuzzyChef Feb 28 '21 at 06:53
  • @Kat correct other tomato sauces do not – mroll Feb 28 '21 at 15:56
  • @FuzzyChef after cleaning the pan from whatever foods bits I will pour in a bit of oil and finish cleaning it with the oil to clean the red stuff. Yes it’s a ceramic nonstick – mroll Feb 28 '21 at 15:58
  • Huh. Maybe it's a property of ceramic nonstick? I've never had anything like that happen on any of my pans. – FuzzyChef Feb 28 '21 at 19:48
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    As it is red and oil soluble, it is likely to be lycopene - why it sticks to your pan, and why only that sauce I don't know, though it could be that extra lycopene is added at some point (I think less than 0.05% doesn't need to be declared(?)). – bob1 Feb 28 '21 at 21:13
  • Bob: I've never had an issue scrubbing lycopene off anything with soap though. – FuzzyChef Mar 02 '21 at 06:57

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I know this will sound disappointing, but I don't that you will ever find a non-trivial answer to the question.

First, what sticks is the sauce. Once it is made into a sauce, it is physically a single entity, no longer separable into tomato, basil, etc. Of course, it is not all of the sauce that sticks, for example the water is no longer there, and as somebody else mentioned, the red pigments like the lycopene are there - but it is practically impossible to sit down with a list and check off, "hemicellulose is present, sucrose is present but much smaller percentages than in the original, the eugenol is completely missing", but if somebody could, and would, do it, there would be no more precise a name for that wild mixture than "sauce residue".

The second part of your answer is the why. The problem is, surface physics is complicated, and the physics of something as wildly complex as sauce much more so. An expert materials scientist with access to enough samples of the pan, the sauce, a well-equipped lab and enough time could probably find out, and have some answer like, "the starch particles in this sauce are not as round as in others" or "this sauce uses powdered tomatoes grow d to the exact size to get stuck to this particular coating after they've been hydrated in sauce, then heated". Or sounding else of that kind. But without the experimentation, it is impossible to find out.

rumtscho
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  • My first thought was something on the line of "particles too small to be removed with water, due to surface tension (etc.) getting stuck in the surface structure of the pan"... Interesting, though, as the stains in my pans usually come in one of two _flavors_: "Cannot be removed at all" or "easily removed with scrubbing"... - The first kind is then, by definition, a part of the pan and not a stain... ;) – I'm with Monica Mar 02 '21 at 08:49