How to add category name in order confirmation mail?

[michal_michal]

I want to display category name next to product name in order confiramtion mail, for example: Red wine (cat name):Beaujolais Nouveau(product name) price:xxx, I'm using virtueMart 2.x, i know i must edit invoice_items.php  but i dont know what to add. Please help me with this modyfikation.