I conducted an interesting experiment. I have a dinner roll recipe that incorporates potato flakes. Potato flakes are very bulky and take up a lot of space for the amount of mass, so I wondered if I could replace the flakes with potato starch. I wasn’t sure it would work, because my research indicated that potato flakes were made from potatoes that were cooked then dehydrated, whereas potato starch was made from raw potatoes before dehydration.
As I was mixing the dough, it was way more gloppy than normal. In fact, I ended up having to add almost 1/2 cup of flour before it came together, still very sticky. After the dough rose in an overnight retardation, the dough was dry as Play-doh. I had a hard time forming them into balls because the refused to stick to the counter. I had to spray some water on the counter. I’m letting them rise now, which I’m not sure they will do very readily, and I’m interested in seeing how they bake up.
My analysis of the problem is that my normal potato flakes absorb a lot more moisture than potato starch, at least with cold water, which is why I had to add so much flour. However, I suspect the long overnight fermentation gave the starch plenty of time to absorb the moisture in the dough, leaving it dry. So the net result is that the dough is short 30-40 grams of water.