Reader Kim, writes:
I have a couple lactose-intolerant folks in my house, and we sometimes bake with rice milk instead of cow’s milk. I’ve noticed a stark difference in the leavening and texture of pancakes and popovers when I use regular milk. With regular (cow’s) milk, the pancakes and popovers are fluffier and rise higher. With rice milk, they don’t rise as much, and have a gummier, gooey texture. Is it the magic of milk solids? The protein content? The fat? The type of sugars?
Hey Kim! The answer is starch. Rice milk is basically a suspension of rice endosperm particles in water. Each of those particles is made up of bunches of individual starch molecules: amylose and (especially in the case of rice) amylopectin. Cool or cold, the rice suspension flows easily. Heat it, however, and some different things start to happen. The little bunches of endosperm start to break apart into their component starches, and as those bushy little amylopectin molecules disperse they begin to restrict the flow of the liquid around them. The liquid gets thick and sticky.
You can see this behavior at work when you overcook rice or make risotto. It’s that starchy goo that’s in your pancakes. On the surface one might be tempted to think that even though the starch is gummy, it might help the pancakes rise, but that isn’t the case. Having no gluten, the rice starch can’t contribute to the pancake’s structure. Rather it only gets in between the gluten molecules and they try to link up with each other, preventing the formation of a gluten network and undermining the rise. So that’s what’s going on, Kim. Hope this helped!