What happens to Gluten in a deep fryer? (Allergy related)

I work in a restaurant, and it seems “gluten allergies” are trendy these days. I get all these people freaking out about the tiniest trace of gluten that could be in something (maybe) and the web isn’t much help in sorting out the facts. So, could you smart Dopers help me out with a few things?

Now, for the disclaimer: I understand what celiac disease is, and I respect that those affected by it need to avoid gluten at all costs. Because of this It is important to know which foods can be called “gluten free” and which cannot.

Now for my question. If I cook a gluten free food in a deep fryer (say french fries) that has previously had gluten based foods in it (say battered fish), are the french fries still gluten free? Lets assume for the sake of convenience that the two foods had not been in contact in any other way, and separate utensils were used in preparation. The only source of gluten contamination could be the fryer oil. Can gluten survive the 350˚F of the deep fryer, and cause a problem for a celiac sufferer?

Now, I picked french fries, as an example, but the web is full of tales of french fries that contain gluten. Please assume for this question that the french fries we are using are gluten free.

I don’t know the answer to your question, but the apparent increase in complaints about gluten may not be altogether unwarranted.

The prevalence of undiagnosed Celiac Disease has increased dramatically in the US in the past 50 years, possibly due to the fact that the high-gluten “dwarf” variant of *Triticum Aestivum *now accounts for over 99% of the wheat grown here today.

Gluten is by far the most toxic of the commonly consumed foods in the US.

Well, when I bake bread gluten survives the 400 F of the oven for at least 20 minutes, so yes, gluten can survive in a deep fryer

If a food with gluten - say something battered with a wheat-based coating - is fried in the deep fryer bits of that breading could wind up in the deep fryer fat and potentially get onto whatever is dunked into it next, such as up-until-then gluten-free french fries.

So, if you’re cooking gluten-containing foods and non-gluten foods in the same deep fryer fat either the gluten free stuff goes first or you’re looking at cross contamination. Yes, for the very sensitive this could cause a problem.

OH, BS - gluten is “toxic” only if you have celiac or an allergy. To everyone else it’s a healthy form of protein. If you’re looking for “toxic” start with things like excessive alcohol consumption.

Apparently Celiac disease is brought on by allergy to certain gluten peptides.
Now when you toss something organic into a deep fryer, it will emit liquids and suspended solids into the frying oil. Put something glutenaceous in hot oil, and you will end up with free gluten in your oil.
350°F isn’t all that hot as far as a protein is concerned. Witness the existence of such foods as bacon or fryed chicken as proof that high temps aren’t instant death for proteins. 500°F will destroy many organics quickly, but not 350°F. So whatever gluten leaches out of your wheat batter will have some sort of half-life in the fry oil. Since it’s the sequence of the peptides (eg Arg-Glu-Pro-Ala-Ala-Trp…) that matter in terms of allergy, and not the protein structure, that half life is likely to be at least on the order of minutes, and possibly in the range of hours to days.


Gah! Please don’t spread information that is just flat out wrong. An allergy is an inappropriate reaction mediated by the IgE antibody. Celiac is an autoimmune disorder of the small intestine that in the presence of gluten causes atrophy of intestinal vilii.

Kindly bite me.
Those of us who aren’t students anymore don’t need to use the term in the precise fashion required to pass prof whatshisname’s test. And when we don’t, we’re NOT being “flat out wrong”, we’re just not being persnickety and obsessive.

Here’s a more commonly used def:
See, it’s pretty general, and that’s how I was using it.

Now tell us all about the halflife of immunoactive peptides in hot grease, if you can.

Bullshit. By that metric (anything that causes a negative reaction is toxic), histamine is the most toxic substance around.

(Please refrain from claiming histamine is toxic. There are limits around here.)

Dial it back a notch. This is GQ.

samclem Moderator

If this were just any website I wouldn’t care, but we’re supposed to be fighting ignorance here.

And it’s not an idle difference - if you enter an ER saying you have an “allergy” gets you a different reaction than saying “I have celiac”. They are two separate disorders. It’s like saying a heart attack and a stroke are the same thing because they both involve the cardiovascular system. They’re not.

Let Broomstick dail it back a notch.
He wants to get all prim and accusatory, I’m going to answer him.

Broomstick, we’re not in an ER, we’re in GQ. ER language rules don’t apply here anymore than courtroom evidence rules apply i the Pit.

Dial it back a notch, and look up the AA composition of the active subsequences and tell us if they contain any amino acids that are particularly prone to oxidation.
That’d go towards actually answering the question posed in the OP.

The OP’s question has already been answered. The answer is that cross contamination of foods cooked in a deep fryer that has had gluten containing foods cooked in it is a reasonable expectation.

You, are on the other hand, said two medical disorders are identical when they are not. Maybe you don’t care, but I don’t want those wandering past to take as fact something that is incorrect.

Her, FTR.

Conflating a disease and an allergy is bad grammar?

If someone has a gluten intolerance - and especially if they have a wheat allergy or celiac (two different things - actually THREE different things) fry oil that has been used to fry gluten containing stuff (onion rings) has been contaminated. For the individual in question, that may or may not matter, but trace amounts of gluten are sufficient to cause a reaction in many people.

In your restaurant, you have a few choices. If anyone says they have issues with gluten, say that your fry oil is used for gluten containing foods and let them make their own choice. OR have separate oil set up - if you are seeing a lot of gluten intolerant folks, saying “we have a separate fryer we use that we don’t use except for gluten free foods” will win you a lot of loyal customers.

Thank you for the responses. I was hoping to hear that a protein in a deep fryer would break down enough to eliminate its allergy causing qualities, but i see now that it does not.

Dangerosa, my official stance on fried foods and gluten concerns at this point is “if you have a severe gluten intolerance, we suggest that you avoid all deep fried foods.” I would love to add a third fryer to my line, but I don’t have room.

Broomstick, Normally, bread is baked to an internal temperature of 180˚F. I was asking about gluten existing at 350˚F, so I don’t see how your first statement is relevant. Also, saying “Gluten allergy” and “celiac disease” in a hospital may get you different reactions, but not in a kitchen. For the purpose of this question, they are the same thing.

Amblydoper - I have severe Celiac disease, and your answer is exactly what I would want to hear. I want to be steered away from anything “risky.” People being people, you will probably have someone complain. But I think you’ll find most people will be grateful that you warn them.

Well, if someone has celiac and they accidently eat some it may make them miserable, but it’s not considered a medical emergency.

If someone with a gluten allergy eats gluten it could potentially kill the person within minutes if the reaction is severe enough.

So yes, the difference isn’t trival when you’re talking about potential consumption.

Though yes, for the question of “does gluten survive the deep fryer” it’s not so important.

Alcohol is toxic enough that it can kill you if you were to force yourself to drink a massive amount of it, but the same is true of water. Excessive consumption of alcohol can cause fatty liver disease, but so can drinking excessive soda/fruit juice (fructose). And just about all of the epidemiologic evidence I’ve seen suggests that moderate drinkers are healthier than teetotalers.

Celiac disease is characterized by antibodies to two components of the gluten compound (alpha-gliadin and transglutaminase). But wheat gluten contains several other potentially toxic forms of gliadin (beta-gliadin, gamma-gliadin, omega-gliadin, etc.) that currently are not tested, so Celiac disease and gluten sensitivity appear to be underdiagnosed:


One in three doesn’t sound like very good odds to me.

More on gluten toxicity here:


Aside from my question on the soundness of your sources, NONE of that contradicts my statement that gluten is only “toxic” if you’re sensitive to it.

Most adult human beings, when you look at the entire world, can’t digest lactose, yet here in North America there’s milk and milk products everywhere. OMG! We’re bing poisoned! Um… no we’re not. If you can digest milk as an adult go ahead and eat it. If you can’t, don’t. Same thing for gluten. If you can eat it without a problem go ahead. If you’re sensitive to it, don’t.

Exactly. The protein may denature, in that it will uncoil and cease to function as it normally does, but the actual chain is unlikely to hydrolize, especially in the not-so-wet environment of a fryer. Well, there is moisture in the food, but still 350 °F isn’t all that hot.

It has affected me personally - I was diagnosed via Endoscopy in 2003. If I eat Fries (chips in the UK) that are contaminated cue 10-12 visits to the toilet and 4 days of stomach cramps. not nice :frowning: