What is seeping out of my key lime pie? For Valentine's Day this year I attempted to make my wife a Key Lime Pie.  I followed Emeril's recipe, with one small modification: I replaced the granulated sugar in the crust with a 1:1 ratio of light brown sugar.  The key lime juice was freshly squeezed, not packaged.

In case the link ever goes away, the ingredients are:

Base: graham cracker crumbs, light brown sugar (original called for white), 1/2 stick butter melted
Filling: condensed milk, key lime juice, whole eggs
Topping: sour cream, powdered sugar, lime zest

The pie was delicious and held together great.  I'm a good cook, but a very inexperienced baker, so overall I was very happy with how my first attempt turned out.

However, after about 3 hours in the fridge this viscous liquid started seeping into the pie pan (see picture below).  My assumption is that this is lime juice and/or sugar somehow escaping, but I don't really understand how or why that would be happening.  My other thought is that it might have to do with the molasses from the brown sugar in the crust, although that seems less likely to me (I've made plenty of pies with similar crusts that didn't have this problem).

As described in the recipe, I baked the crust by itself, put the filling in, baked it for 15 minutes together, and then put it in the fridge for 2 hours before cutting.  

So, my questions:


What is seeping out of my pie after about 3 hours of refrigeration?
How can I prevent this in the future?
What you have there is simply water seeping out of the gel and bringing some dissolved stuff with it. This is known technically as syneresis. What will help is to add something stabilize the gel. Xanthan gum is probably the easiest thing to use. You can find it at health food stores or Whole Foods because gluten-free bakers use it a lot. Start with 1/8 teaspoon pureed into your filling. Sprinkle it over the filling liquid before mixing, and put it through a sieve before baking to catch any clumps.