Reader Rob writes:
Hi Joe, I have looked through a lot of raised doughnut recipes, and very few ever seem to use milk powder as an ingredient. I assume this is for the proteins, but how come you use it whereas other recipes don’t? Maybe delve into the science behind it?
Hey Rob! Nice question. Milk powder does a few things in a baking application. As you point out it adds protein, and that along with the extra sugars can be handy in terms of getting a darker, more golden finish. It also add flavor, another nice feature especially in fast rising breads like doughnuts and white loaves which tend to be bland because of the extra-quick yeast action. However the big benefit of dry milk is tenderness. The fats and the milk solids undermine gluten formation so the finished product is less rigid than it would otherwise be. That’s especially desirable in a raised doughnut since the crusts can come out of the oil rigid to the point that they shatter when you bite into them. The longer you let the doughnuts rest the softer the crusts get, but since I generally like to hand them around when they’re warm I go the tenderizer route.
Foiling the action of gluten has other benefits for doughnuts. If the dough isn’t terribly stretchy then the bubbles in it tend not to get very big. That’s good because a big open crumb can be a pain in the neck when you fry. The big open spaces can push the expanding doughnut out into weird shapes, or create giant open cells which can break open and fill with oil. Those big cells are also inconvenient if you’re filling your doughnuts with jam as all the filling tends to pool up in one place. In general in a yeast doughnut you want a fine, fluffy, even crumb. So you see there are a lot of good reasons for milk powder in a doughnut dough.
I should add that the finer your milk powder the better as the solids and fats spread out more evenly through the dough. That translates to a finer structure that is at once more tender, fluffier, taller AND stronger. King Arthur milk powder is especially fine and I heartily endorse it. Thanks again, Rob!