Assessing the influence of spontaneous fermentation on consumer emotional responses to roasted arabica coffee in a biometric approach

Beyond sensory quality, food-evoked emotions play a crucial role in consumers acceptance and willingness to try, which are essential for product development. The link between fermented coffee sensory characteristics and elicited emotional responses from consumers is underexplored. This study aimed to evaluate consumers' acceptability of spontaneously fermented and unfermented roasted coffee through self-reported sensory evaluation and biometrics assessment. Self-reported liking in 15-cm non-structured scale, multiple choice of negative, neutral, and positive emojis, and subconscious emotional responses from 85 regular coffee consumers were analysed. Their relationship with the pattern of volatile aromatic compounds were also investigated. Fermented (F) and unfermented (UF) coffee beans with light- (L), dark- (D), and commercial dark (C) roasting levels were brewed and evaluated along with gas chromatography-mass spectrometry measurement. Multivariate data analysis was conducted to explore the inner relationships among volatile compounds, self-reported liking, and biometrics. Unfermented-dark roasted coffee (UFD) had highest overall consumer liking response ± standard error (8.68 ± 0.40), followed by the fermented-dark roasted (FD) at 7.73 ± 0.43 with no significant differences (p > 0.05). Fermented light-roasted coffee was associated with lower liking scores and negative emotional responses. In contrast, dark roasted coffee, which was linked to positive emojis and emotional responses, exhibited less detected peak area of volatile compounds contributing fruity and vegetative aromas, such as benzaldehyde, furfuryl acetate, 2-acetyl-1-methyl pyrrole, and isovaleric acid, potentially as negative drivers of consumer liking. Findings from this study could guide coffee manufacturers in developing specialty coffee if spontaneous fermentation is offered.