## 4 Discussion and Conclusions  
Although from a food safety point, coffee is considered a shelf-stable product, changes in roasted coffee aroma over time due to out-gassing and chemical reactions lead to perceivable differences in coffee aroma and \"freshness\" [4; 6]. While previous studies looked at the impact of storage conditions on ground or brewed coffee, this study used coffee consumers to determine the impact of the roast level and storage conditions on the aroma of freshly ground coffee beans. Consumers arranged a total of 12 samples (6 different coffees presented in blind duplicates) in a PM task and provided descriptors for the groups and samples. The created product consensus maps showed high agreement among the consumers in how they perceived the coffees, with a clear separation between light and dark roast samples. Light roast coffees were described by the consumers as _light, sweet, floral, fruit, chocolate_, and _non-traditional_ while dark roast coffees elicited terms such as _dark_, _strong_, _smoky_, _nutty/roasted_, _earthy_, _burnt_, and _appealing_. Changes in coffee aroma due to storage conditions were also picked up by the consumers as newly roasted, freezer-stored, and room temperature-stored coffees were separated. The light roast samples seem to differ to a smaller degree among the three storage conditions while the dark roast coffees showed less perceivable differences between the newly roasted and freezer-stored coffees, but those two samples clearly differed from the room temperature-stored dark roast coffee. This could be explained by differences in overall volatile content. Previous studies showed that light roast coffees overall show lower levels of instrumentally measured aroma volatiles [27], which could explain less aroma resulting from lightly roasted beans. This observation was substantiated by the instrumental measurements of 48 previously reported important coffee volatiles, which showed more volatiles decreasing to a larger extent in the dark roast coffees from the newly roasted to the stored samples. Based on these findings, we recommend storing newly roasted beans in a freezer and refrain from storing at room temperature. This is especially important for dark roast coffee where the changes were much more dramatic compared to the light roast samples. While this study provides some first important insights, future work is needed to determine whether these findings transfer to other single origins or roast levels, as coffee roasting is a very complex processing step and the outcome is highly dependent on the green bean starting material, as well as the roasting conditions. Secondly, in this study, consumers only smelled the freshly ground beans but did not taste the brewed coffee. Although many coffee consumers smell coffee, it would be important to test whether similar trends would be found if the coffees were tasted. Third, it would be worthwhile to test whether a more focused test, such as a discrimination test, would allow consumers to pick up smaller differences between the samples. Especially for the light roast samples that were perceived as being more similar, independent of the storage condition, a discrimination test could lead to better product differentiation. Last, it would also be interesting to test whether the level of expertise or involvement matter in how small a difference between coffee samples could be picked up by consumers in a PM task. For example, beer enthusiasts showed higher agreement with beer professionals than beer novices in a PM task of premium Danish beers [21] and, similarly, Italian wine consumers with high knowledge displayed similar perception of similarities as wine professionals (winemakers, enologists) [28]. Overall, consumer product maps mimicked the instrumental measurements in that the lighter roast coffees showed smaller changes due to storage conditions compared to the dark roast samples.