Roasting
- Espresso is roasted darker than other sorts of coffee.
- European roasters (particularly in the North/Scandinavia) generally roast lighter than American. E.g. Starbucks French roast coffee is not far from “pure charcoal” with very little left of the original coffee flavour.
- Coffee is preferably consumed between 1 and 4 weeks after roasting. Earlier than 1 week and it will usually have a noticeable smoky aroma. It’d be interesting to see how old the non-capsule coffee was (after roasting) that the researchers used, and also the time between roasting and packaging of the capsules
- During roasting, coffee beans develop an internal CO2 pressure, resulting in a continuous flow of CO2 out of the beans over a period of a few weeks, protecting the coffee from developing (rancid) off flavours. Hence: one should buy a decent grinder as well as whole beans.

Brewing
- A capsule-based cup is the result of brewing on far less coffee compared to a proper espresso machine (about 1/3). If the amount of furan is in the cup, the ratio in the pure capsule vs non-capsule coffee is hence even higher

So, the conclusion should perhaps be to buy a grinder and whole beans and stay with expensive speciality coffee from Scandinavia

Thanks for the tip, …again