Does Heat Destroy Gluten?

Does Heat Destroy Gluten?

In short, yes gluten can be killed but the heat has to be a lot higher than any fryer can reach. We spoke to a few different people and did some extensive research to find if there was any truth to "does heat kill gluten"
The most common irritating comment we hear as Coeliacs has to be "frying at high temperatures destroys gluten", why some restaurants and chip shops think this I don't know, it's not like there is any proof, unfortunately there isn't much proof on the contrary either.

We decided to do a bit of research though and contacted a few people as well as simply googling to see what we could find in terms of heat killing gluten, we wanted to actually run an experiment but have yet to find anywhere that can help us conduct the experiment since it seems to have never been done before (feel free to contact us if you have access to a lab and can help us with this!)

First off gluten is a protein molecule, you can't kill a molecule. Simple biology. So when someone says heat kills gluten, they are way off the mark, now if they say heat destroys the gluten that might be slightly different but still not entirely true.

When we spoke to Tricia Thompson, a nutrition consultant, researcher and writer from Boston who specialises in gluten free and is the creator of the website Gluten Free Dietician and founder of the company Gluten Free Watchdog she provided us with some interesting information which was in an article she wrote. Now they haven't conducted an official test at their lab but Thom from the lab that runs all the tests for Gluten Free Watchdog does provide some insight:-

As far as gluten being broken down by the heated oil, this is unlikely. According to my Joy of Cooking cookbook, the best temperature for deep frying is 365 degrees F. According to Thom, this is not a high enough temperature to completely hydrolyze gluten, at least in the short term.

"Gluten proteins are extremely resilient and can't be broken down easily with temperature or time. The oil might have some effect on the protein tertiary (i.e., 3-dimensional) structure, BUT remember some breads are cooked at 500 degrees F for 10-15 minutes (pizza) and the gluten remains intact. So the short answer is that hot oil for the most part can not be trusted to completely hydrolyze gluten."

Except from Tricia Thompsons "French Fries" post

To hydrolyse gluten means to break down the structure, while the heat may damage the gluten, it isn't hot enough to destroy the gluten molecule completely.

When gluten is subject to high heat a process called "denaturing" happens to the enzymes, which basically irreversibly changes the shape of the enzyme. Unlike other proteins though gluten is very tough and hard to denature, gluten can be broken down to it's primary structure (first breaking down the quarternary, tertiary and secondary structures) but it still remains a gluten molecule which is still gluten at the end of the day.

According to at least three articles, the one provided to us by Tricia above, this one which is actually about grilling, but same concept about heat applies and this article with information provided by a chemist, all claim 500F/260C or even higher (650 in the last one) is needed to destroy gluten. They may all be American but same information applies in the UK too.

This is also the reason some sourdough bread's are believed to be gluten free after cooking even though they are made with wheat flour, because they are cooked at a high heat for 500F/260C for a 15 minutes. While it's possible the gluten could have been destroyed in the heat would you risk it? I know I wouldn't.

In terms of the fryers destroying the gluten, if it takes over 500F or 260C to denature the gluten molecule fully the chip shop fryer must be hotter than normal as the heat of the fryers we asked about and found online were only between 130C and 200C (392F highest which is over 100 degrees lower than that needed for full denaturing of gluten). While this heat may destroy some of the structures of the molecule its not enough to make it safe for coeliacs, the gluten would still be gluten.

While there is not definitive studies on the degradation of gluten in fryers I think based off the information from dietitians, chemists and lab technicians provided in the articles it is safe to say that heat doesn't destroy gluten, or at least destroy it fully, so if your chip shop says "oh the fryer is so hot the gluten is destroyed", make sure you turn round, walk out and find a chip shop that uses a dedicated fryer!

Your Comments

I've recently eliminated gluten from my diet and wow do I feel better. I soon searched at what temperature with time gluten could be destroyed and came upon this blog. It looks as though gluten is more resilient than I imagined.
I do believe that it is a misconception to think that if something is cooked at a certain temperature that means the entire volume of the thing being cooked reaches that temperature. The boiling moisture will prevent it from reaching the oven temperature. For example, a turkey may cook for 4 hours at 350 degrees, but it is considered done when the enternal temperature reaches 165.
I believe that if it takes over 500 degrees and time to destroy gluten, nothing that actually reached that temperature would be edible or could be digested anyway. I rather certain that pizza dough would catch on fire after the moisture boiled away and before it reach 500.

Lawrence Luther - 7th January 2018

The question here seems to be cooking temperatures. I need to know how much heat would be required to degluten an oven rack so I can put my gluten free pizza on it. I'm thinking at some point, even the toughest molecule becomes char. Is all black char gluten free?

DP - 26th April 2018
Alison @ Coeliac Sanctuary replied to this comment on 27th April 2018

It has to be very hot. Tests have only ever gone up to around 300C and the gluten isn't destroyed at that point, most ovens only go to around 240C. Gluten molecules will still be in the char, but black as far as tests have shown. You'd be best putting a gluten free pizza on a tray on top of the rack so it's not in contact.

I have a stone floored pizza oven that goes to 500 celcius. If I cook a gluten based pizza in it, and then leave it just sitting that temperature for 15min, do you think the gluten would be essentially destroyed? Trying to decide if I need to buy another oven :(

Tom - 10th December 2018

I must admit to being astonished that a protein could/would survive any significant exposure to temperatures as high as 260C.

As far as "destroying a molecule" - you can destroy a molecule, for example by hydrolysis, in which case the molecule undergoes a complete transformation as it is cleaved. Generally, most proteins do denature at moderately high temperatures - which is one reason why processes like pasteurization and sterilization work - but indeed, there are some very stable proteins (for example - prion proteins),that are difficult to denature. Is this also true for gluten?

Richard Mitchell - 10th July 2019

Lots of scientific errors or inconsistencies in this article. I can help with a few and implore the author to contact me, this article is near the top of the google search list and has the potential to be very helpful if the information is ironed out.

First off. Denaturing is the process that occurs when a protein is heated until it loses its structure and becomes a long ribbon, instead of being folded up. At this point the gluten can be broken down by the enzymes in the stomach. Enough heat being applied will cause the ribbon to break into pieces.

One problem though, is that after the heat is reduced some proteins refold back into their shape; I don’t know if gluten does this, but it’s in the checklist to find out.

Gluten is not an enzyme, it’s a protein structure that spontaneously occurs when the flour is mixed with water, specifically two other proteins (glutenin and Gliadin) react in the presence of water.

The reason baking bread (even at 500F) doesn’t effect the gluten even though the environment is hot, is because the bread does not get over 212F. You know this, because it still contains moisture, the moisture would all have boiled off if it got much higher than that. It it got much higher than 450, it would ignite.

There is a temperature at which the gluten denatures, and a temperature at which it partially or fully hydrolyses. The temperature at which the prices starts to permanently denature or hydrolyse in oil is about 374F, but at that temperature it takes 30 minutes of frying. At 451F it takes 10 minutes. Fryers usually operate at 365F, so likely very little destruction of the protein.

On gas stove was necessary to keep 233 °C (451 °F) for 10 minutes to have absence of GIP detection. In range 190-200°C (374-392°F) incubation for 30 minutes was needed to have absence of GLuten detection. Tests in temperatures below 190°C (374°F) showed presence of GLuten at 10 and 20 minutes.

Joshua white - 9th February 2020

The smoke points of cooking oils tend to be far below the denaturing point of gluten, so anyone trying to clean oil in between uses by heating it to 600f for 20min would start an oil fire.
This inability to break down gluten by chemical forces isn't disconnected from our body's inability to break down gluten through biological forces.

Patrick Kniesler - 15th March 2020

I think it would be fun to test dry foods like biscuits, toast and shortbread. As this would remove the limit that moisture puts on the internal temperature. It might be interesting to consider the temperatures that are reached in fudge and toffee preparation. These are pretty high and are not fully dehydrated, (does water aid hydrolysis?). What temperature would a multigrain flapjack attain internally?

Toby - 25th May 2020

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