if(itemStack.hasTagCompound()){
itemStack.getTagCompound().removeTag("ench");
}
NBTTagList newnbttaglist = new NBTTagList();
NBTTagCompound nbt = item.getTagCompound();
nbt.setTag("ench", newnbttaglist);
item.setTagCompound(nbt);
if(itemStack.hasTagCompound()){
itemStack.getTagCompound().removeTag("ench");
}