Baking without dairy can be a challenge. Milk is not tricky, butter is not particularly tough. But sour cream, yogurt, buttermilk, and other cultured products can be hard to approximate. (You can just forget about cheese.)
Of these, buttermilk is the easiest. You can sour soy milk in the same way that you would sour cow milk to make faux-buttermilk, by adding about a teaspoon of white or cider vinegar or lemon juice to a cup of milk. Use an unsweetened, unflavored soy milk.
Sometimes I will make a richer “buttermilk” by combining equal parts unsweetened, unflavored soy yogurt and soy milk, then adding a teaspoon of lemon juice. I use this in my vegan black chocolate layer cake, and in my non-vegan buttermilk cornbread, and it works beautifully, adding moisture and density.
Sour cream is difficult indeed. Non-dairy “sour cream” products are made with many thickeners for the sake of texture, and not all of them react well to heat. The texture of your finished product can suffer badly. Also, their fat contents are not the same as that of dairy sour cream, which means that in terms of chemistry and physics they will not perform the same way. I learned the hard way that it wasn’t possible to make a sour-cream pastry dough for kolaci with non-dairy sour cream. The dough wouldn’t perform correctly without my adding enough extra flour to turn it into something much closer to a pretzel than a pastry — inedible.
Some recipes, however, will do well with soy yogurt instead of sour cream if you do the following: the day before you want to use it, pour the unsweetened, unflavored soy yogurt into a colander lined with a damp clean kitchen towel and let it drain as much as it can for about 24 hours. Then, just before you are going to use the drained soy yogurt, whip about a teaspoon of lemon juice and a tablespoon to a tablespoon and a half of neutral oil (grapeseed, canola) into the yogurt to increase fat and acidity. This will work well in things like sour cream coffee cake. I still wouldn’t try it in pastry dough, though.
Yogurt generally speaking can be substituted for with soy yogurt. Once in a while you may find that due to one of the thickeners present in the soy yogurt, you’ll end up with a texture problem, but if you try to buy the least thickener-happy soy-yo you can find, that should be diminished.
I have not yet tried baking with coconut milk yogurt. I am a little suspicious of how it would perform because the protein content is so different. Also, I haven’t been able to find a source for unsweetened coconut milk yogurt. If anyone who reads this has experience baking with coconut milk yogurt, would you let me know how it went?
