iOS game freezes at a collision after startup

Hi. Each time i start the game and it detects a collision i see it freeze for 1-2 seconds.This only happens after i just started the game.If i reset the game without closing it with Application.loadlevel this problem is not there anymore.What could cause this problem and how can i fix it? Thank you

You can create a pool of these particle systems where you can store the particle systems so that you do not have to instantiate it every time required.