title: Influence of foam structure on the release kinetics of volatiles from espresso coffee prior to consumption.
abstract: 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. The structure parameters foam volume, foam drainage, and lamella film thickness at the foam surface were quantified using computer-assisted microscopic image analysis and a digital caliper. The above-the-cup volatile concentration was measured online by using PTR-MS and headspace sampling. A correlation study was done between crema structure parameters and above-the-cup volatile concentration. In the first 2.5 min after the start of the coffee extraction, the presence of foam induced an increase of concentration of selected volatile markers, independently if the crema was of high or low stability. At times longer than 2.5 min, the aroma marker concentration depends on both the stability of the crema and the volatility of the specific aroma compounds. Mechanisms of above-the-cup volatile release involved gas bubble stability, evaporation, and diffusion. It was concluded that after the initial aroma burst (during the first 2-3 min after the beginning of extraction), for the present sample space a crema of high stability provides a stronger aroma barrier over several minutes.
authors: Nestlé Research Center, P.O. Box 44, 1000 Lausanne 26, Switzerland.
authors: Susanne
authors: S
authors: Dold
authors: Christian
authors: C
authors: Lindinger
authors: Eric
authors: E
authors: Kolodziejczyk
authors: Philippe
authors: P
authors: Pollien
authors: Santo
authors: S
authors: Ali
authors: Juan Carlos
authors: JC
authors: Germain
authors: Sonia Garcia
authors: SG
authors: Perin
authors: Nicolas
authors: N
authors: Pineau
authors: Britta
authors: B
authors: Folmer
authors: Karl-Heinz
authors: KH
authors: Engel
authors: Denis
authors: D
authors: Barron
authors: Christoph
authors: C
authors: Hartmann
mesh_terms: D055598:Chemical Phenomena; D003069:Coffee / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D009812:Odorants / Q000032:analysis; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D003069:Coffee; D055549:Volatile Organic Compounds; D014867:Water