"Added gluten" refers to the inclusion of a protein called gluten in certain food products. It is added to improve the texture, elasticity, and structure of the food, particularly in baked goods like bread. Full definition
Since we are making this bread to test the flours, I didn't add any gluten. (sourdoughhome.com)
Anything higher and it comes out too dense (without adding gluten or changing yeast quantity). (laurafuentes.com)
They state that their ketchup does not contain added gluten but because their products aren't tested they can't guarantee that they are GF. (glutenfreedaddy.com)