Dynamism of coffee aroma perception: a study combining real-time sensory and instrumental techniques

The perception of flavour is a complex and dynamic process especially for coffee. The combination of sensory and in vivo instrumental measurements in real time is an original approach to get better insight regarding this phenomenon. We applied this approach to study the influence of roasting degree and sugar addition on coffee flavour perception and volatile release during consumption. 4 espresso coffees were analysed: medium and dark roasted Arabica coffee, with or without sugar. Temporal Dominance of Sensations (TDS) describes the in-mouth evolution in terms of dominant sensations and was carried out by 18 trained judges using a 9-attribute list (sweet, sour, bitter, astringent, roasted, burnt, caramel, nutty and vegetal). Qualitative and quantitative measurements of the volatiles reaching olfactive receptors were performed simultaneously by nose-space analysis (NS) with Proton Transfer Reaction-Time of Flight-Mass Spectrometry known as a direct injection mass spectrometric technique. The roasting process significantly affected both sensory dominant perceptions and aroma release. When roasting degree increased, more volatile compounds were released and in larger quantity. This was described sensorially with a greater dominance of the attributes burnt, roasted, astringent and bitter. Sugar addition did not significantly affect the aroma release in the nose as demonstrated by the NS profiles of judges whereas it completely changed the perception of coffee in the mouth. Expectedly, sweet taste became dominant over bitter and sour but it increased the global the flavour complexity with Caramel and Nutty notes by reducing the roasted or burnt ones. Besides, the treatment of mass spectrometric NS data using clustering methods revealed two different release behaviours of mass peaks, which could be a possible way to identify some TDS aroma markers. These results emphasis the presence of taste-taste and taste-smell perceptual interactions during coffee drinking and the potential of combining dynamic methods to study the perceptual interactions.