Beer is a complex beverage. Beer flavour is a multisensory experience in which, in addition to aroma volatiles, CO 2 , ethanol, bitterness (hop acids) and sweetness all contribute. To investigate the interactions between these fundamental components, a model beer system was developed using representative ingredients. Samples, selected according to a D-optimal design, were assessed by sensory profiling techniques by a trained panel. Predictive polynomial models generated from mean panel data described variations in the attributes as a function of design factors. Results show that CO 2 significantly impacted on all discriminating attributes, including suppression of sweetness and modification of bitterness. A number of complex interactions with design factors showed the effects of CO 2 to be dependent upon component concentration and level of carbonation. CO 2 interacted with hop acids to increase carbonation and tingly perception, which increased linearly with hop acid addition but only at low levels of CO 2 . Ethanol was the main driver of warming perception and complexity. In agreement with other studies, ethanol enhanced sweet perception and also formed some complex interactions with hop acids and CO 2 to modify various attributes, illustrating its ability to interact with both gustatory and trigeminal stimuli. Whether the mechanisms behind these interactions originate at the gustatory periphery or at higher centres in the brain is an area for further investigation. This study provides an in-depth assessment of important flavour components in beer and advances the limited data available on the effects of CO 2 on sensory perception using a commonly carbonated beverage.

A model beer was created to investigate the effects of ethanol, carbonation and hop acids on volatile release (ethyl acetate, isoamyl alcohol and phenethyl alcohol) using both headspace analysis and in-nose measurement during consumption. None of the factors were found to impact on equilibrium headspace partitioning, however headspace sampling after short term decanting revealed minor and compound specific effects of each of the components. When measured in-vivo, hop acids had no significant effect on volatile delivery; however ethanol significantly increased the delivery of volatiles during consumption. This increase was sustained throughout the release profile. Carbonation was found to increase the release of ethyl acetate and isoamyl alcohol during the first release peak after swallowing, but had no significant effect on phenethyl alcohol. Furthermore, ethyl acetate was increased by carbonation in the second peak after swallowing, but this effect was not found to be persistent in subsequent peaks. These results indicate a trend between the compound's air-water partition coefficient and the effects of carbonation in-vivo. The effects of ethanol and carbonation seemed to be independent and therefore an additive effect is possible. This study highlights the difference between data collected by headspace and in-vivo means.

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