Yes, there are several different types of gluten, and the differences matter more than most people realize. Gluten isn’t a single protein. It’s a collective term for a family of storage proteins found in wheat, barley, rye, and related grains. Each grain produces its own version, and even within a single wheat kernel, gluten is made up of two distinct protein groups with very different properties.
The Two Proteins Inside Wheat Gluten
What we call “gluten” in wheat is actually an aggregate formed from two major protein types: gliadin and glutenin. Together they account for roughly 80% of the total protein in a wheat kernel, with glutenin making up about 50% and gliadin about 30%. These two proteins do very different things when you add water and start kneading.
Glutenin provides elasticity and strength. It’s the reason bread dough snaps back when you stretch it. Gliadin does the opposite: it gives dough its extensibility and viscous, flowing quality, allowing it to stretch without breaking. The balance between these two proteins determines how a flour performs. A high-glutenin flour makes chewy bread. A flour with more gliadin relative to glutenin produces softer, more extensible doughs better suited to pastries or flatbreads. Bakers have been selecting for this balance, often without knowing the biochemistry, for centuries.
Gluten Proteins in Barley, Rye, and Oats
Barley, rye, and oats each produce their own versions of gluten-like storage proteins, and each has a distinct name. In barley, they’re called hordeins. In rye, secalins. In oats, avenins. All of these share similar amino acid sequences with wheat gluten, which is why barley and rye are off-limits for people with celiac disease.
These proteins can be further sorted by molecular weight into high, medium, and low groups. Barley hordeins, for instance, include B-hordeins, C-hordeins, D-hordeins, and gamma-hordeins. Rye secalins similarly split into omega-secalins, gamma-secalins, and high-molecular-weight secalins. The structural similarities across all these grains reflect their shared evolutionary ancestry as grasses, but the practical differences between them can be significant, particularly when it comes to immune reactions.
Oats are a special case. Avenin is structurally more distant from wheat gliadin than hordeins or secalins are. Most people with celiac disease tolerate oats well, but a 2025 clinical study found that 38% of celiac participants showed measurable immune cell activation in response to purified oat avenin, and 59% experienced acute symptoms. One participant out of 29 had a severe inflammatory response similar to what wheat triggers. This is why some celiac guidelines recommend caution with oats even when they’re certified gluten-free.
Why Some Gluten Types Trigger Celiac Disease
Not all gluten proteins are equally harmful to people with celiac disease. The primary culprit is a subgroup called alpha-gliadins, specifically those encoded by the D genome of modern bread wheat. These alpha-gliadins contain a fragment known as the 33-mer peptide, a chain of 33 amino acids that carries six overlapping segments the immune system recognizes as threats.
What makes this fragment so potent is that human digestive enzymes can’t break it down. It forms naturally in the gut during normal digestion, survives intact, and then gets modified by an enzyme in the intestinal lining. Once modified, it binds tightly to immune cells, triggering the inflammatory cascade that damages the small intestine. Shorter peptide fragments covering only one or two of those immune-triggering segments produce a much weaker response. The 33-mer’s unusual resistance to digestion and its density of overlapping trigger sequences make it the single most immunogenic piece of the gluten puzzle.
Omega-gliadins and gamma-gliadins also contribute to the immune response, but alpha-gliadins from the D genome carry the highest celiac-triggering potential.
Ancient Wheat vs. Modern Wheat
Einkorn, emmer, and spelt are often marketed as easier-to-digest alternatives to modern wheat, and there is a real biochemical difference in their gluten, though it’s not what most people assume.
The key distinction is chromosomal complexity. Einkorn is a diploid wheat with two sets of chromosomes. Emmer is tetraploid (four sets). Modern bread wheat is hexaploid (six sets), carrying the A, B, and D genomes. That D genome is the one encoding the most immunogenic alpha-gliadins. Einkorn lacks it entirely, and emmer does too.
Ancient wheats also have a dramatically different ratio of gliadin to glutenin. Modern bread wheat typically has a gliadin-to-glutenin ratio of about 1.5 to 3.1, with a mean around 2.5. Einkorn’s ratio averages 6.5 and can reach as high as 12. Emmer averages 4.9, and spelt sits around 3.3. This means ancient wheats contain proportionally far more gliadin relative to glutenin, which produces softer, more extensible doughs that don’t rise as well for fluffy loaves.
The absence of the D genome in einkorn and emmer means they lack the most potent celiac-triggering peptides. However, they still contain other immunogenic gliadin sequences and are not safe for people with celiac disease. For people with non-celiac gluten sensitivity, the picture is less clear and more individual.
Deamidated Gluten in Processed Foods
Food manufacturers sometimes chemically modify gluten to improve its functionality, creating what’s called deamidated gluten. The process alters the side chains of gliadin’s amino acids, changing the protein’s physical properties. Deamidated gluten foams better and emulsifies more easily, making it useful in processed foods, sauces, and even cosmetics.
Research on mice has shown that deamidation alone (without breaking the protein’s backbone) actually reduces allergenicity when the protein is eaten. Deamidated gliadin fed to mice produced no significant allergic antibody response compared to untreated gliadin. However, when deamidation is combined with partial breakdown of the protein chain, creating smaller fragments that can penetrate skin, the picture reverses sharply. Mice exposed through the skin to this doubly modified gluten developed severe allergic reactions, with body temperature dropping over 4°C and symptom scores significantly higher than all other groups.
This finding became practically relevant after cases in Japan and Europe where hydrolyzed wheat protein in facial soaps caused new-onset wheat allergies. The concern is specific to skin exposure to modified gluten, not to eating deamidated gluten in food. But it’s a reminder that processing changes gluten’s behavior in ways that matter immunologically.
How Fermentation Changes Gluten
Long sourdough fermentation partially breaks down certain immunogenic gluten peptides. In one controlled study, sourdough bread showed reductions of 42% to 59% in specific immunogenic peptide concentrations compared to conventional bread after simulated digestion. The most targeted peptides dropped by more than half.
The catch: sourdough fermentation did not decrease the total immunogenic peptide concentration. It altered which peptides survived digestion and in what amounts, but it didn’t eliminate them. Sourdough bread still contains gluten and is not safe for celiac disease. Some people with milder gluten sensitivity report tolerating long-fermented sourdough better than conventional bread, and the partial peptide breakdown may explain why, but the reduction is incomplete.
Grains That Don’t Contain Gluten
Corn, rice, sorghum, and millet are all grasses, and they all produce prolamin storage proteins. Corn’s version is called zein, and rice produces oryzenin. But these proteins have different amino acid sequences than the prolamins in wheat, barley, and rye. They lack the proline-rich and glutamine-rich repeating segments that resist digestion and trigger the celiac immune response. This is why corn and rice are naturally gluten-free and safe for people with celiac disease, despite being grain crops in the same botanical family as wheat.
Pseudocereals like quinoa, buckwheat, and amaranth aren’t even grasses, so their seed proteins are structurally unrelated to gluten. They’re reliably safe for gluten-free diets, though cross-contamination during processing is always worth checking for on labels.