I've been baking 100% whole wheat sandwich loaves and consistently getting a gummy, dense crumb — even when the internal temperature reaches 98°C (208°F).
I've read that bran particles in whole wheat flour physically cut gluten strands during mixing, which weakens the dough structure and leads to poor moisture retention after baking.
Does adding vital wheat gluten to whole wheat bread prevent a gummy crumb?
Vital wheat gluten can help, but it doesn't necessarily fix a gummy crumb.
Gummy crumb often comes from too much water for the flour you are using...or under baking...or cutting too soon, before the crumb is set. It could also be a result of over proofing.
Before you go the vital wheat gluten route, try baking a little longer, cooling completely, maybe a lower hydration formula. Then, if you want to try wheat gluten, maybe 3%.