title: Influence of water quench cooling on degassing and aroma stability of roasted coffee.
abstract: Coffee roasting experiments with air cooling versus water quench cooling were carried out on laboratory scale with a fluidized-bed hot air roasting system (200 g batch size) and on production scale with a rotating bowl roaster (320 kg batch size). Two series of coffees with different water contents resulted, which were stored at 25 degrees C under normal atmospheric conditions. Carbon dioxide desorption was followed and stability of selected aroma compounds was tested with headspace solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and stable isotope labeled compounds as internal standards. Degassing is faster in water-quenched coffees with higher moisture content, but pore size distribution in the different coffee samples did not correlate with degassing behavior. Bean firmness, which increases with increasing moisture content, might have an influence on degassing. Air- and water-quenched coffees exhibit similar stability of most aroma compounds despite different degassing behavior. However, evolution of dimethyl trisulfide was different in coffees with increased water content. This suggests higher thiol oxidation rates, a factor that is cited to be related to a faster loss of freshness attributes.
authors.affiliation: Institute of Food Science and Nutrition, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.
authors.forename: Juerg
authors.initials: J
authors.lastname: Baggenstoss
authors.forename: Luigi
authors.initials: L
authors.lastname: Poisson
authors.forename: Regina
authors.initials: R
authors.lastname: Luethi
authors.forename: Rainer
authors.initials: R
authors.lastname: Perren
authors.forename: Felix
authors.initials: F
authors.lastname: Escher
mesh_terms: D040503:Coffea / Q000737:chemistry*; D003080:Cold Temperature; D004355:Drug Stability; D005511:Food Handling / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D009812:Odorants / Q000032:analysis*; D012639:Seeds / Q000737:chemistry*; D014867:Water
chemical_list: D014867:Water