As you can guess, the main ingredient in a Krispy Kreme doughnut is wheat flour, but there is also some added gluten, soy flour, malted barley flour, and modified food starch; plus egg yolk, non-fat milk, flavoring, and yeast. I suspect a low-gluten flour, like cake flour, is probably used in the original mix to make the doughnuts tender, and then the manufacturer adds the additional gluten to give the doughnuts the perfect framework for rising. I tested many combinations of cake flour and wheat gluten, but found that the best texture resulted from cake flour combined with all-purpose flour. I also tried adding a little soy flour to the mix, but the soy gave the dough a strange taste and it didn't benefit the texture of the dough in any way. I excluded the malted barley flour and modified food starch from the Krispy Kreme original glazed doughnut recipe since these are difficult ingredients to find. These exclusions didn't seem to matter because the real secret in making these doughnuts look and taste like the original lies primarily in careful handling of the dough.