Influence of Water Quench Cooling on Degassing and Aroma Stability of Roasted Coffee

• Published in: Journal of agricultural and food chemistry Vol. 55; no. 16; pp. 6685 - 6691
• Main Authors: Baggenstoss, Juerg, Poisson, Luigi, Luethi, Regina, Perren, Rainer, Escher, Felix
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.08.2007
• Subjects: Biological and medical sciences; carbon dioxide; Coffea - chemistry; coffee (beverage); coffee beans; Coffee, tea and other stimulative beverage industries; Cold Temperature; cooling; degassing; desorption; dimethyl trisulfide; Drug Stability; Food Handling - methods; Food industries; food quality; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; headspace analysis; odor compounds; Odorants - analysis; roasting; Seeds - chemistry; solid phase extraction; solid phase microextraction; Water; water content; water quenching cooling; water treatment; Stability; coffee structure; flavor stability; Carbon dioxide; water quenching; solid-phase microextraction; Coffee; Flavor; Roasted coffee; Solid phase microextraction; Degassing; Cooling water; Quality; roasting; Aroma; Structure
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf070338d

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 °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. Keywords: Coffee; roasting; water quenching; solid-phase microextraction; flavor stability; carbon dioxide; coffee structure