It has been observantly stated that we drink with our eyes. Thus, the presentation of the beer in the glass in terms of its foam head, clarity/brilliance and colour is very important.
In terms of flavour, the foam head is critical. Beyond foams tactile perception on the upper lip and in the mouth, it is in effect a gas exchange medium. Foam is constantly evolving CO2 that can bring some aromas along for the ride. Depending on the solubility of the flavour compounds, they will either concentrate in the foam or the foam will act as a barrier to their liberation.
Typically the hydrophobic (water insoluble) characters such as hop bitterness and aroma oils will favourably concentrate in the foam along with spices such as coriander and orange peel. Conversely, the absence of foam accentuates hydrophilic (water soluble) flavours such as malty and caramel, and the fruity esters such as banana (isoamyl acetate) while enhancing the perception of undesirable butterscotch (diacetate) flavours.
Beer glass shape, material and thickness impacts on the longevity of the foam, and whether or not the aromas are caught and presented to the drinkers nose. Thicker glasses will reduce the rate of beer warming thus tending to improve the persistence of the foam. Long cylindrical shaped pils glasses will have a higher surface to volume ratio, thus warm more quickly. Importantly, glasses with a relatively narrow brim compared to their body tend to concentrate aromas (i.e. hoppy) in the glass and present them to the drinkers nose. Such glasses also result in reduced CO2 loss and more stable foam.
Some may counter, most beer is drunk from a bottle. Well, yes it is, and beer bottles are often attractive and convenient in their own right. However, the drinker is largely missing out on the flavour cues extolled above. Bottles being glass are not opaque, particularly with the current fashion for clear (flint) and green varieties, so that they allow the drinker to clearly view foam formed as a result of the drinking action. Lastly, in attempting to compare beer with wine, in at least more up market settings, it would certainly be considered to be passé or uncouth to drink wine from the bottle!
(via: belgianshop newsletter)