Jackitup is spot on, the good news is that the calcium in the milk helps to strengthen the gluten forming proteins in the flour and the lactose (milk sugar) content helps with the browning of the crust, like I said, that's the good news, the bad news is the amount of milk you're adding (liquid milk I assume) really doesn't contribute to either of these effects as the amount is much too low. To get any realized effect you need to have the liquid milk at about 40% of the total liquid (40% liquid milk + 60% water = 100% of the total liquid added). Or is you use dry milk solids you can use 5% but remember to increase the dough absorption by 1% for each 1% milk solids added. Also keep in mind that lactose sugar is not metabolized by bakers yeast so it is not a source of food for the yeast to feed upon. Additionally, if using liquid milk it is a good idea to scald the milk before using it as this will help to improve its baking properties. Due to the cost of milk we really don't see much milk being used anymore, instead we use soy flour to replace the protein content of the milk and calcium sulfate to provide the calcium and whey to provide the lactose (whey solids are about 33% lactose, and because lactose is the least sweet of all the sugars there is essentially no sweetness associated with whey or lactose).
Tom Lehmann/The Dough Doctor
