Characterization of water mobility in dry and wetted roasted coffee using low-field proton nuclear magnetic resonance

• Published in: Journal of food engineering Vol. 81; no. 3; pp. 572 - 579
• Main Authors: Mateus, M.-L., Champion, D., Liardon, R., Voilley, A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2007; Elsevier
• Subjects: Biological and medical sciences; Coffee; Coffee, tea and other stimulative beverage industries; Decay; Drying; Evolution; Food engineering; Food industries; Foods; Fundamental and applied biological sciences. Psychology; General aspects; Moisture content; Nuclear magnetic resonance; Roasted coffee; Spin–spin relaxation; Walls; Water mobility; Spin–spin relaxation; Water mobility; Roasted coffee; Characterization; Water; Spin spin relaxation; Spin-spin relaxation; Mobility; NMR spectrometry; Low field
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2006.12.015

Roasted and ground coffee was studied by low-field 1H nuclear magnetic resonance at various water contents and temperatures. The spin–spin relaxation times ( T 2) were measured with single pulse free induction decay (FID) and Carr–Purcell–Meiboom–Gill (CPMG) sequences. Four relaxing components were distinguished: the solid population was observed with FID sequence at T 2s ∼9 μs; the other three populations, measured with the CPMG sequence, corresponded to an apolar phase, the coffee oil, and two polar phases. The two polar populations, observed at T 2m ∼6 ms and ∼27 ms (for coffee with 50% water content at 90 °C) were attributed to water in cell wall polymers and in water filling cells lumen. The T 2 values appeared relatively insensitive to temperature, showing an Arrhenius type evolution with no break due to an important structure change. Furthermore, the intensity of the mobile phase increased as a function of time up to ∼10 min after wetting, providing information about water absorption dynamics in roasted coffee.