Understanding the dynamics of perception by the combination of sensory and instrumental methods: preliminary results of a study on coffee

Eating and drinking are complex experiences during which different dynamic sensory processes (e.g. mastication and salivation) occur modulating the perception of aroma, taste and texture of foodstuff over the time. Thanks to a sensory method developed in the past few years and called Temporal Dominance of Sensations (TDS) [1] the evolution of sensations in-mouth during the consumption can be measured. The objective of the study was to investigate the effect of roasting degree and sugar addition on the perception of dominant sensations in a expresso coffee. Then the temporal aspect of in-vivo aroma release and its impact on sensory perception was examined by Nose-Space analysis [2,3] performed on panellists during TDS evaluation by mean of Proton-Transfer-Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS). Two different types of expresso coffee (medium (A) and dark (B) roasted) with and without sugar, were evaluated in 3 replicates by a group of 18 panellists trained on TDS method. The panellists had to select the dominant sensation between a list of 9 flavour attributes (3 taste/sensation and 5 aroma/retro-odour attributes) during a 60s evaluation. In parallel to sensory evaluations, the nose-space of the panellists were monitored by mean of PTR-ToF-MS to follow the release of volatile organic compounds (VOC) during the coffee consumption and TDS evaluation. Furthermore the headspaces of 4 coffee samples were analysed by PTR-ToF-MS to characterise the aroma profiles of the assesed samples. The dominance curves obtained with the TDS data showed an evolution of dominant sensory properties over the time and differences between coffees in relation to roasting degree and sugar addition. Medium roasted coffee (A) was differentiated from the dark one (B) by a stronger and longer dominant sour taste in the first part of the evaluation then the absence of burnt aroma dominance replaced by a roasted note and at the end the bitter taste was less dominant and less persistent. The addition of sugar in the coffee modified as expected the dominant perceptions of tastes but also of aroma. The panellists seemed to perceive more differences between samples at the beginning of the evaluation than at the end but some differences among panel responses were observed. The PTR-ToF-MS measurements allowed to differentiate the coffee samples in term of VOC profiles and to trace the changes in the aroma release over the time explaining partly the differences of perception in-mouth between panellists, coffee samples (impact of roasting and sugar) and phases of consumption. After analysis of raw mass spectral data [4,5] volatile compounds were tentatively identified in the headspace of the coffee and nose-spaces of the panellists. There were significant differences among panellists in terms of aroma release during coffee consumption