10
$\begingroup$

I've always seasoned my cast iron pans with vegetable oil because that was what I was taught. I'd done some research before, and even came across this StackExchange post on asking the best oil for the job.

To my dismay however, when I tried doing some research myself, all sources pointed to blog posts, particularly the Sheryl Canter one. There is not a single source on her post and she doesn't seem to be very near a materials scientist. The closest paper I could find to the topic was this one. Other than that, it was all anecdotal evidence, many people claiming many different things.

It felt almost absurd that I couldn't find a paper on something that seemed relatively common to me. This will bug me till the end of time unless I figure it out, so I need to know - does anybody have any real sources on cast iron seasoning or what factors play a part in the polymerization of different oils? Thanks in advance.

$\endgroup$
1

3 Answers 3

1
$\begingroup$

There is this research on Chinese equivalent of seasoning process called "Kitchen God's Blessing" [1].

They argue that the non-stick property of seasoning comes by iron oxide $(\ce{Fe3O4})$ nanoballs.

If they are correct then the oil or its polymers is not exactly what is causing the non-stick property but the those nanoballs on the surface. Their seasoning method is somewhat different however. It uses temperatures up to 450 °C.

Reference

  1. Gao, C.; Yang, N.; Li, C.; Wang, X.; Yu, X.; Zhang, L.; Wei, Z. Seasoning Chinese Cooking Pans: The Nanoscience behind the Kitchen God’s Blessing. Nano Materials Science 2020. DOI: 10.1016/j.nanoms.2020.06.001.
$\endgroup$
0
$\begingroup$

There is 'seasoning' to protect the pan, but on heating the pan, the chemical breakdown products are 'some' things I would not recommend to anyone for continuing good health for yourself or your family (see, for example, Genotoxic and carcinogenic risks associated with the dietary consumption of repeatedly heated coconut oil).

Unfortunately, many oils do breakdown even at low heat, and some at high temperatures, which includes even my favorite healthy (especially when acquired fresh from its harvest) Olive Oil!

However, a safer alternative path may yet exist to resurrect ourselves (but not likely literally).

Electrochemistry to the rescue!

In particular, try employing a sacrificial anode, like a small piece of zinc metal sitting in distilled water plus sea salt, covering your entire pan. Yes, to be explicit, my recommendation on how to best season your iron pan to guard it from future corrosion is zinc metal and saltwater free of oxygen, which unlike an oil coating, is not easily subject to removal or chemical disruption (from air/light exposure).

On the mechanics, your iron metal will no longer be the most anodic metal present, and the zinc may undergo limited anodic corrosion resulting in white ZnO/Zn(OH)2 product. However, even the latter can be consumed in low doses daily whereas, one must be more mindful of iron intake especially with small children. One has also, at low cost and safely, eschewed the dangers of associated heat generated cariogenics from various organics.

Aesthetically, I would also challenge you to compare the results from two iron pans, one stored in the manner I have suggested, to the other pan that was coated in whatever oil-based seasoning formulation you may believe is suitable, after washing both pans.

$\endgroup$
10
  • 2
    $\begingroup$ I think you miss the point. First the seasoning isn't mainly to protect the iron from rusting but rather to get a non-stick coating. Second, the oil polymerizes on the pan, thus it isn't the same as whatever oil you started with. $\endgroup$
    – MaxW
    Aug 22, 2020 at 17:10
  • 2
    $\begingroup$ The dangers of cooking are greatly exaggerated and irrelevant to this question. Most every theoretical worry (PAH, nitrosamines, acrylamide...) has proved irrelevant in the real world. And the oil used in "seasoning" the pan is polymerised to an extent that means it does not contaminate anything (this is very different to repeatedly reusing the same oil to cook). $\endgroup$
    – matt_black
    Sep 21, 2020 at 15:36
  • 1
    $\begingroup$ @matt_black proven where? and by whom? 'the oil used in "seasoning" the pan is polymerised to an extent that means it does not contaminate anything (this is very different to repeatedly reusing the same oil to cook).' high polymers contain free radicals (i.e. oxidized monomers) and can be digested by lipases, which means that yes, you are actually harming your cells DNA as those polymers are released on micro level almost during every cooking process, even more so during cooking with acidic ingredients. $\endgroup$ Sep 18, 2022 at 19:11
  • 1
    $\begingroup$ @matt_black Of course the extent of radicals is important. In comparison to something like Teflon, cast iron pan seasoning releases of a lot more of its coating, and that by daily use. It would have to be first properly measured. "My point it that your theoretical concerns don't show up in epidemiology stats." What epidemiology? There was no long-ranging study nor meta analysis conducted yet on that matter. It is simply an unexplored subject. We can only have some indirect evidence. It is nearly impossible to ascertain the structure of seasoning coating let alone draw any conclusions today. $\endgroup$ Sep 18, 2022 at 20:17
  • 1
    $\begingroup$ @matt_black that is why I wrote that it hasn't been measured, because there was no research on the topic yet. "And do you even have any evidence that what is released contains anything harmful?" Absence of evidence is not evidence of absence. Do you know how scientific method works? "Are there studies showing people who cook using them have high rates of specific diseases? " Are there such studies? Can you name one? There hasn't been. The industry been interested mainly in Teflon, and that was successfully researched. Teflon is well-studied contrary to cast iron seasoning, which it's not. $\endgroup$ Sep 20, 2022 at 9:52
0
$\begingroup$

Well, I came here in search of the same thing so it looks like we are the leading researchers in the field of pyrrolic polymerization on antique cookware. (Frowny face) I similarly reject 100% of the dot com heroes' wisdom available. It's garbage mixed with myth.

Here is what I know: Researching the chemical properties of cooking oil under pyrrolic polymerization is a start. It will teach you a lot but you could get a Ph.D. in the field with how much learning is out there.

I will do my best to summarize what I've learned in the process in the name of comparing notes.

There are three main types of oil we are talking about. Saturated, monounsaturated, and polyunsaturated

Saturated is a solid at room temp because the Vanderwall forces on long straight chains of carbons and no double bonds. Lard or coconut oil.

Monosaturated have one double bond so they have one kink. These a liquid at room temp. Olive oil

Polyunsaturated therefore are the kinkiest of the groups having more than one double bond. These polymerize very well but are very reactive and often aren't suitable for cooking due to their tendency to oxidize and go rancid at temperature. Grapeseed

The science says the presence of double bonds creates the possibility of covalent cross-linking which is a powerful and permanent bond. It's also impervious to corrosion under natural conditions.

The presence however of long uniform chains of carbon in unsaturated oils allows for uniform sheets of patina. So each has its place and none are "best"

Those are things I know. Here is what I've found to be the case from experimentation:

Lard makes a good low-maintenance patina but I find that it isn't as durable as I'd like in some cases. Particularly in the presence of tomato sauce. In some cases, I've found that I'm back to bare metal on the edges just through normal cooking.

Grapeseed creates an incredibly hard patina that I've seen chip under mild abuse. Worse, its polymer is lipophobic so it resists additional layers and creates a patchy, unreliable patina. The more layers, the worse the effect gets until the oil just beads up and rolls off preventing any additional layering. The science tells us that there are cross-links that are awesome but in practice, I've found this patina to be sticky and hard to cook with owing to the thinness of just one layer in many places. I tried hard to love grapeseed but I don't.

The best luck I have had is a mix of 1:1:1 unsaturated, mono, and polyunsaturated oils. So coconut, olive oil, and grapeseed seem to bridge the gap between the weaknesses of each oil and have given me the best results yet.

In theory, I am using the unsaturated fats to fill in the inconsistent holes of the poly and mono crosslinks and reduce the available oxygen for the more reactive oils to rancidify. I have also found that the unsaturated patina isn't nearly as lipophobic so I can make several layers and get a very smooth, hard, durable surface that food doesn't stick to.

Lastly, the temp I use has proven to be the most crucial part. Too hot, the patina cracks and falls off like dry paint chips, too cool and it's sticky. I go 5 degrees over the smoke point of the highest smoking oil. Then I leave it in until I notice the room is less smokey. This step has been a hard-learned one because there is a lot of crappy advice out there.

I would love to see some actual documentation on this so if you find it let me know. Good luck

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.