Foam and the perception of beer flavor and mouthfeel.

Langstaff, S.A. and Lewis, M.J.

Abstract
Following previous studies which indicated a connection between foam quality and the assessment of the flavour and mouthfeel of beers by taste panel members, the question of the extent of the psychological influence of the visual image of the foam head (as opposed to the tactile perception of foam as a component of mouthfeel, or any effects of foam characteristics on the sensory perceptibility of aroma/flavour constituents) on taste test results was investigated in trials using the "R index" procedure, which provides an indication of the minimum degree of difference between samples which is necessary for them to be perceived as different by the taster. Four different beers were used in these trials, either dispensed from directly above the centre of the glass to create a large head, or poured down the side of the glass so as to create little or no foam. In the first set of trials, taste panel members were blindfolded, and the beer samples were served in wine glasses in the hope that slight differences in aroma would be made more noticeable as a result of the bowl shape of the glass. It was found that these glasses caused the foam to be held back as the glass was tilted, so that it did not touch the drinker's lips. This prevented the evaluation of the effect of foam on mouthfeel, but by making it impossible for the tasters to detect foam by touch made the aroma and flavour results more reliable. Although the results varied among the different beers and panel members, in general foamed and unfoamed beers could not be reliably distinguished, suggesting that aroma/flavour effects are minimal. In a second set of trials using plastic cups, blindfolded tasters were able to feel the foam on the upper lip as they drank, while when identical sets of beer samples were served to tasters without blindfolds, the strong visual impact of the presence or absence of foam on their judgement was clearly apparent from the results.
Keywords : aroma beer flavour foam taste test