Minecraft runs out of memory when you switch a lot between worlds

After switching between worlds like 25 times, minecraft runs out of memory

I created 2 new superflat worlds with the "Redstone Ready" template.
Each time i switch to another one of these, the game consumes 60 - 100 mb more ram!

What I expected to happen was...:
I expected to be able to switch between singleplayer worlds as much as i want

What actually happened was...:
Minecraft starts using more and more ram, making it crash because it's out of memory

Steps to Reproduce:
1. Leave current world
2. Join another world
3. Leave this world
4. Join another world
And so on like 25-35 times until minecraft crashes