I think you meant to type 'curdle.' I'm not sure it's a bad thing - I add lemon juice to milk all the time to achieve a buttermilk substitute, and the curds are very soft and blend into the cake well. The main point of buttermilk, or for that matter the lemon-and-milk substitute, is to create an acid liquid to activate the baking soda for leavening. Milk makes the cake richer and affects the crumb. What does your recipe look like? Are you trying to achieve more of a lemony flavor? You'll want to use lemon zest for that, not just juice.
Lemon juice will curdle milk. Juice isn’t a very good flavoring agent, When using citrus, it’s best to use the zest. The oil in the peel contains both aroma and flavor. Not only is the flavor more pronounced with zest, but you don’t have to deal with the curdling issues.
Hmmm........curdle does sound more apt. LOL
I must have been really tired to not catch that.
I think someone has posted this issue before. I have always used citrus juice in my citrus cakes and they have never curdled. Of course, I don't mix everything the way other people do, so that might be why I've never had a problem with it. I find that zest is bitter. I use zest in frosting but not cake. All that sugar in the frosting cuts the bitterness, but I find it does come through in the cake.