A number of recipes involve soaking meat in milk, buttermilk or yogurt, for example several Middle Eastern lamb recipes and traditional American southern fried chicken. Someone I'm cooking for is allergic to dairy. What dairy-free substitute would give the most similar effect and why?
Milk has been used in marinades for a long time, and it does work. It is thought that it is the calcium in the milk that activates enzymes in the chicken rather than enzymes in the milk tenderizing the chicken, see this article for the science. This means you can use soy, rice, or any milk substitute, but you'll get the best result from the one with the most calcium. This article lists the mg of calcium per 1 US cup (235ml) of cow's milk and substitutes:
- Cow's milk: 300mg
- Rice milk: 283mg
- Coconut milk: 41mg
- Soy milk: 19mg
So it looks like Rice milk is the best substitute from a tenderizing perspective.
There are other ways of tenderizing chicken, pineapple for example does a great job, however if you want authentic middle eastern milk substitutes are the way to go.