Baking – How to substitute skim milk for dry milk in a muffin recipe

There is less of a difference than you might think. Heck, with the addition of a little calcium chloride (to help bind the milk particles), you can even make cheese with skim milk. I flipped through Harold McGee's section on low-fat milk, and he doesn't give any warnings about using it in cooking.

Of course, keep in mind that your result won't have quite the same texture. I doubt you'll notice unless the milk is the primary ingredient in the sauce (and there's no other thickening agent) or primary liquid in the dough. If I was forced to come up with a way to adjust to using low-fat, I'd probably add a little more milk if I was going for flavor, or a little less if I was going for texture.

The short answer is yes; the longer answer depends on what kind of soy milk you're buying and how you plan to use it. I've used soy milk in my breads and cakes without noticing much of a difference in texture, but I use the unflavored, unsweetened versions of it (especially in cake-baking, as many recipes call for vanilla and some soy milks have vanilla in them). I avoid "light" soy milk when making creamy dishes or sauces because I want them to have the creamiest texture possible. If you're using soy milk in a soup or stew, don't allow it to boil because that can cause the "milk" to curdle (and add your acids at the end of cooking, also to avoid curdling). Oh, and be aware that some brands of soy milk are very sweet (you can buy it unsweetened, though); the sweetness might not work well in some dishes.