Common Myths and Questions – Gluten Free Necessity

Some people wonder if gluten can be "cooked off". Photo by Stefan C. Asafti on Unsplash With a lifelong prescription of a strict gluten-free diet comes the tendency to wonder whether that diet may be made a little easier by some special kitchen hack that lays waste to gluten. Maybe you have asked yourself if it is possible to destroy gluten in the cooking or baking process. The highest temperatures used in typical food preparation including toasting, baking, frying, deep frying, pressure-cooking, microwaving, and boiling are not sufficient to break gluten down to the point that it’s safe to consume for those with celiac disease or gluten intolerance. Gluten denatures and breaks down at around 570° F or 300° C. We’ll explain why each of these cooking methods won’t destroy gluten, but first we need to have a very short and simple gluten biology lesson. Gluten Remains Intact Even in High Heat Gluten is a protein, and a protein’s function is determined by what amino acids the protein is made of and the shape the amino acids can fold into. Basically, gluten and other proteins are folded amino acid structures. When a protein is denatured, its structure is broken down and therefore it loses its function. Many proteins denature between 120-175° F, (50- 80° C), but gluten proteins do not denature until much higher temperatures are reached, over 570° F or 300° C. Most food preparation methods, such as frying, deep frying, baking, or toasting, use temperatures much lower than the 570° F required to denature or destroy gluten. Even if cooking temperatures of 570° F or greater were used, the food would not be exposed to the high temperature long enough for the internal temperature of the food to reach gluten’s denaturing point. We’ll walk through some examples of why these cooking methods don’t work to destroy gluten. Does baking food destroy gluten? Temperatures used in residential grade ovens during standard baking processes are not hot enough to break down or destroy gluten. Most residential grade ovens have a maximum baking temperature of 500° to 550° F (260° to 290° C), but gluten doesn’t denature (break down) until 570° F (300° C) or higher. Baking gluten-containing food in the oven does not make the food safe for those with celiac disease or gluten intolerance. While the max baking temperature of 550° F of residential ovens is close to the 570° required to denature gluten, most foods are baked at lower temperatures than the max 550°. Also, keep in mind that the temperature your oven is set to does not equal the internal temperature of the food that is being baked. Example: Bread is usually baked at temperatures between 350 and 475°F (180 and 246°C) and is considered done when the internal temperature reaches 190° F or 90° C. Let’s say you try to destroy the gluten in the bread by baking it at 600° F or 315° C (which your oven probably can’t achieve under normal circumstances). If you manage to set your oven to 600° F, your loaf will heat up to 212° F (100° C) until all the water has evaporated, completely drying out your bread, before continuing to heat up to 600° F. Whatever comes out of the oven will most definitely be inedible charcoal, even if all the gluten is denatured. Fun fact: Commercial pizza ovens can get up to temperatures of 700 to 900° F, which is much hotter than the standard max 550° F of residential grade ovens. However, pizza is not cooked in the oven long enough for the internal temperature of the pizza to reach the required 570° F to denature the gluten. Can you imagine a restaurant serving you 600° pizza? The pizza would be unsafe to handle and inedible. Do ovens get hot enough to destroy gluten? Residential grade ovens do not get hot enough during normal baking temperatures to destroy gluten, but do get hot enough during the self-cleaning mode to destroy gluten. Gluten is denatured or destroyed at temperatures above 570° F (300° C) and ovens in self-cleaning mode will reach 930° F (500° C). While the self-cleaning mode of ovens does get hot enough to destroy gluten, you’d be left with only ashes of food after the self-cleaning mode is complete. Does toasting food destroy gluten? Photo by Daniel Salgado on Unsplash Toasters and toaster ovens do not get hot enough to destroy gluten. Gluten denatures or is destroyed at temperatures greater than 570° F (300° C), but standard toasters only get up to temperatures around 310° F and toaster ovens have a max temperature around 500°F (260° C). Toasting gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. Since toasters do not get hot enough to destroy gluten, you may be wondering if you need to get a dedicated gluten-free toaster. For a long time, organizations like Beyond Celiac have recommended that those with celiac disease or non-celiac gluten sensitivity (gluten intolerance) have a dedicated gluten-free toaster so that gluten-free bread does not come in contact residual crumbs of gluten when toasting. One research study, however, seems to indicate otherwise. A study performed in 2019 by the Celiac Disease Program at Children’s National Health System and the Harvard Celiac Disease Program found that gluten-free bread toasted in shared toasters had either no detectable amounts of gluten after toasting, or less than 10 parts per million (ppm) gluten, which meets the US’s standard of 19PPM gluten or less for being considered gluten-free. In short, researchers toasted gluten-free bread in toasters that had previously toasted gluten-containing bread and found that gluten-free bread picked up no or almost no residual gluten-containing crumbs. While this study shows promise and seems to indicate that we may not need to worry as much about gluten cross contact when toasting as we previously thought, it is important to remember that this was only one study, and more studies need to be performed to validate its findings. I have celiac disease and plan on keeping my dedicated gluten-free toaster. Can deep-frying destroy gluten? Deep fryers do not get hot enough to destroy gluten. Gluten is denatured or destroyed at temperatures above 570° F or 300° C, but the temperature of the oil in both home and commercial grade deep fryers generally doesn’t exceed 400° F (200° C). Deep frying gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. As deep frying doesn’t destroy gluten, those with celiac disease and gluten intolerance need to be careful about eating deep fried food like fries when eating out. Even if the fries are gluten-free, they’re generally not considered safe for those who need to avoid gluten if they are fried in a deep fryer that also deep fries gluten-containing food. You’ll need to check with each restaurant you eat at if their deep fryer fries gluten-containing food. If you could get the oil in a deep fryer up to the temperature of 570° F required to denature gluten (which you likely can’t because most oils will start smoking & burning before that temperature), you’d burn the entire food item to crisp trying to get the internal temperature of the food to the required 570°. Does pan frying food destroy gluten? Photo by Louis Hansel on Unsplash Frying pans and skillets do not get hot enough to destroy gluten. Gluten is denatured or destroyed at temperatures above 570° F or 300° C, but frying pans and skillets only reach temperatures of about 400° F or 200° C during normal cooking. Frying pans and skillets can get up to 600° F (315° C) on high heat, but food isn’t cooked long enough for its internal temperature to reach the required 570° F to denature gluten. Frying gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. Does boiling food destroy gluten? Boiling water does not get hot enough to destroy gluten. Gluten is denatured or destroyed at temperatures above 570° F or 300° C, whereas boiling water cannot get above 212° F or 100° C under normal conditions. Boiling gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. Since boiling food does not destroy gluten, gluten-free pasta that is cooked in water that previously cooked gluten-containing pasta can contain trace amounts of gluten after cooking. When ordering pasta at a restaurant, it’s wise to ensure that the restaurant cooks their gluten-free pasta in separate water from their gluten-containing pasta. Do pressure cookers get hot enough to destroy gluten? Pressure cookers do not get hot enough destroy gluten. Gluten is denatured or destroyed at temperatures above 570° F or 300° C, but most pressure cookers have a max temperature of about 250° F or 120° C. Pressure cooking gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. While boiling water and steam can’t exceed temperatures of 212° F or 100° C under normal circumstances, they can when put under pressure. While pressure cookers do get hotter than normal boiling water and do a great job at cooking food, they leave all the gluten in the food intact. Can microwaves destroy gluten? Photo by Lissete Laverde on Unsplash Food cooked in microwaves under normal conditions does not get hot enough for gluten to be destroyed. Gluten is denatured or destroyed at temperatures above 570° F or 300° C, but microwaved food would only reach temperatures of 212° F or 100° C before all the water in the food would evaporate and the food would start burning. Microwaving gluten-containing food does not make the food safe for those with celiac disease or gluten intolerance. Does the stomach destroy gluten? The stomach does not destroy or denature gluten enough for it to be safe to consume for those with celiac disease or gluten intolerance. Gluten will partially degrade in the stomach before reaching the small intestine but will still be sufficiently intact to cause a reaction for those with celiac disease. Proteins in the food you eat are broken down by digestive enzymes. This process begins with your saliva and continues through your gastrointestinal tract. Gluten is somewhat resistant to degradation and therefore can reach your small intestine intact. Fun fact: Researchers have discovered enzymes that do break down gluten more effectively that stomach acid. These enzymes have been considered as treatment options for those with Celiac Disease, but the enzymes are essentially neutralized by the stomach’s digestive enzymes and acid. (Your stomach is one harsh place, but not harsh enough for gluten, apparently). Does running over gluten at 90 miles-per-hour destroy gluten? Road rage and general anger or frustration towards the inconveniences of living a gluten-free life does not destroy or alter the gluten enough to make it safe for someone with Celiac Disease to eat. Nice try though. A Very Deep Dive into Destroying Gluten Photo by Tomasz Filipek on Unsplash Gluten is more than just a protein. It is actually a group of proteins including gliadin and glutenin proteins. Gliadin acts as the main trigger for an inappropriate immune response in the small intestines of those with celiac disease. The different types of gluten proteins (gluten, gliadin, glutenin) and the quality of gluten proteins (good, bad, in-between) will vary in the conditions of their denaturation. Calorimetry is a process by which scientists (particularly food scientists) can determine many of the thermal properties of something by measuring the heat that is released and absorbed while they burn it in a controlled fashion. You may have guessed by the name calorimetry that the calorie content of food is one of these properties that can be determined. (Is your mind blown yet?) Protein denaturation is yet another. My wife, Sydney, who is a biologist, did a lot of digging into various peer reviewed journals for a solid answer about the temperature at which gluten proteins denature (see sources below). Generally, the journals showed denaturation temperature values around 570° F or 300° C, but various factors impact this number. For example, one cool study looked at the gluten content from a high-quality loaf of bread and a low-quality loaf of bread. They performed some differential scanning calorimetry up to about 480° F or 250° C. The proteins in the low-quality bread were shown to have a denaturation temperature of 390° F or 200° C whereas the proteins in the high-quality bread showed no denaturation temperature under 480° F. In other words, the proteins in the low-quality bread denature and degrade at a much lower internal temperature. This shows that quality is one factor that will affect the denaturation temperature of gluten. Now, don’t think you can go find some low-quality, gluten-containing breads to toast and eat if you have Celiac Disease. Your bread will still be inedible charcoal if you heat it up to 390° F or 200° C. Sources: My Wife, Sydney Caputo, I., Lepretti, M., Martucciello, S., & Esposito, C. (2010). Enzymatic strategies to detoxify gluten: implications for celiac disease. Enzyme research, 2010, 174354. https://doi.org/10.4061/2010/174354 Dhaka, V., & Khatkar, B. S. (2016). Microstructural, thermal and IR spectroscopy characterisation of wheat gluten and its sub fractions. Journal of food science and technology, 53(8), 3356–3363. https://doi.org/10.1007/s13197-016-2314-9 Falcão-Rodrigues, M., Moldão Martins, M. & Beirão-da-Costa, Maria. (2005). Thermal properties of gluten proteins of two soft wheat varieties. Food Chemistry. 93. 459–465. https://doi.org/10.1016/j.foodchem.2004.10.023 Rumińska, W., Markiewicz, K. H., Wilczewska, A. Z., & Nawrocka, A. (2021). Effect of oil pomaces on thermal properties of model dough and gluten network studied by thermogravimetry and differential scanning calorimetry. Food chemistry, 358, 129882. https://doi.org/10.1016/j.foodchem.2021.129882 Schofield, J.D., Bottomley, R.C., Timms, M.F. & Booth, M.R. (1983). The effect of heat on wheat gluten and the involvement of sulphydryl-disulphide interchange reactions. Journal of Cereal Science, Volume 1, Issue 4. 241-253. https://doi.org/10.1016/S0733-5210(83)80012-5 Singh, H. & MacRitchie, F. (2004). Changes in proteins induced by heating gluten dispersions at high temperature. Journal of Cereal Science, Volume 39, Issue 2. 297-301. https://doi.org/10.1016/j.jcs.2003.11.004