I was trying to make white chocolate truffle.....but when I melted my white chocolate and added lemon juice to it, it curdled and there was huge chocolate butter floating on top of my mixture...can anyboody help with this.
Lemon juice is still mostly ... water.
Water to molten chocolate (white or not - there is cocoa butter in either), unless in the form of cream and in a sufficient amount that completely changes texture (giving you a ganache), is generally known to do exactly what happened in your case - seize the chocolate.
When heated, the lemon will badly curdle the molten mixture of cocoa fat and milk solids (lemon is used to curdle milk into cottage cheese, for example).
To avoid this, you should add a bit of molten butter and cream, and add a drop of lemon at the very end after taking the mixture off the flame and after cooling it a bit (but before it solidifies).
Optionally, you can use lemon zest.