The bit that remains is more protein that starch. This is a great demonstration that you can produce raw gluten in your kitchen, and it's handy for when people start spouting pseudo-science about chemicals in their food.
Some people seem the think that the gluten that gets added to store-bought bread is an artificial chemical made in a laboratory. This shows that it is quite natural.
Um, I thought gluten was a naturally-occurring part of certain grains, namely wheat and rye and barley (especially wheat, since it's such a huge staple food in the West). It gets added to a lot of stuff (after extracting it from wheat of course), usually to make it stickier, so it's used a lot in baked goods, pastries, etc.
The problem with it is that a small but significant portion of the population either allergies or sensitivities to it, so it's best that they avoid eating it. The rest of us don't have that problem. But those that do look for alternatives, leading to the rise of "gluten-free" foods today. Traditionally, making GF alternatives has been difficult because the gluten is what helps stuff stick together, so GF bread for instance ended up being hard and very brittle, not chewy like normal bread. But GF stuff has gotten better; I think Xanthan gum is a popular gluten substitute in such foods to give the same effect.
Anyway, I'm usually pretty well-aware of pseudoscience regarding stuff like this, "chemicals" in foods, etc., and I've never heard of anyone thinking gluten is an artificial chemical. The GF faddists (the ones who don't have a genuine allergy or sensitivity) usually just think that GF foods are somehow "healthier", though they have absolutely nothing to base this opinion on. However, it's not all bad: because of all these GF faddists, there's a much, much bigger market for GF foods now than there used to be, so people who are genuinely gluten-intolerant now have far more options than they used to. Just 5 years ago, such a person couldn't eat anything from, say, Domino's Pizza if their buddies were ordering from there, but now they can since Domino's has a GF pizza option.
Anyway, there's plenty of foods which are perfectly natural, yet some people can't eat them because they have allergies to them. I believe some people are allergic to shellfish, for instance. And of course, peanuts are a well-known food allergy; they can outright kill people in small doses, even though there's nothing artificial about a peanut. And don't forget the absolute poisons out there like hemlock, ricin, etc. Those are all-natural too. Even apple seeds have small amounts of poison in them.
Yeah, I don't think we disagree about any of that. "Gluten is a chemical" is admittedly not a very common bit of food pseudoscience, but I do see it occasionally. Sometimes the theory is that the added gluten is some kind of industrial byproduct (half true), and sometimes it's that it is somehow "less natural" than other gluten. For whatever reason I think this view is more closely associated with paleo than GF.