A lot of research is being done in the USA and Europe into flavours for ecigs. Flavours consist of virtually hundreds of aroma chemicals and a lot of guess work is being done as to the possible side effects these chemicals can have when inhaled. Certain aromas have now been identified as being possibly harmful. Diacetyl is one. Diacetyl is found naturally in Cheese and butter. It is not a problem to remove Diacetyl from a formula, or other potentially harmful ingredients. As these flavours are used in ecigs and not in food stuff. One will pick up a difference in foods, but unlikely will one notice a difference in vapours