Sensory evaluation and mixture design assessment of coffee-flavored liquor obtained from spent coffee grounds

Spent coffee grounds are a source of bioactive compounds, including caffeine and other valuable substances, such as volatiles, fats, and alkaloids, which are currently not exploited. In this research, the water content was separated through absolute ethanol extraction yielding a hydroalcoholic solution of volatiles that could be an optimal base for a coffee-flavored liquor. This work was aimed at assessing the potential of coffee-flavored liquor formulations with the use of sensory techniques and mixture design. Based on a mixture experimental design, a total of 17 coffee-flavored liquors, including replicates, were obtained at lab-scale by adding variable amounts of water, glucose syrup, and caramel to a fixed amount of hydroalcoholic extract flavored with vanillin. First, a total of 328 consumers were asked to answer a questionnaire about the attributes of an ideal coffeeflavored liquor and their intensity in order to draw an ideal profile from a consumer point of view. Then, judges trained on the attributes of industrially-produced coffee liquors were involved in two descriptive sensory evaluation sessions of the 17 samples. Data analysis pointed to the coffee-flavored liquors with a sensory profile close to the ideal one. They showed an intense black color (mean score 7) related to a higher caramel concentration in comparison with the other samples. In addition, they scored higher in flavor and body (mean score 7) due to the relative amount of syrup and water. It is noteworthy to mention that the judges regarded these samples as more balanced than the others in terms of alcohol strength, bitterness, and sweetness.