Influence of foam structure on the release kinetics of volatiles from espresso coffee prior to consumption.

The relationship between the physical structure of espresso coffee foam, called crema, and the above-the-cup aroma release was studied. Espresso coffee samples were produced using the Nespresso extraction system. The samples were extracted with water with different levels of mineral content, which resulted in liquid phases with similar volatile profiles but foams with different structure properties.

Unambiguous identification of volatile organic compounds by proton-transfer reaction mass spectrometry coupled with GC/MS.

Interest in on-line measurements of volatile organic compounds (VOCs) is increasing, as sensitive, compact, and affordable direct inlet mass spectrometers are becoming available. Proton-transfer reaction mass spectrometry (PTR-MS) distinguishes itself by its high sensitivity (low ppt range), high time resolution (200 ms), little ionization-induced fragmentation, and ionization efficiency independent of the compound to be analyzed. Yet, PTR-MS has a shortcoming.