Dynamics of water in agar gels studied using low and high resolution ¹H NMR spectroscopy

• Published in: International journal of food science & technology 2010-12, Vol.45 (12), p.2502-2507
• Main Authors: Davies, Erika, Huang, Yang, Harper, Jason B, Hook, James M, Thomas, Donald S, Burgar, Iko M, Lillford, Peter J
• Format: Article
• Language: English
• Subjects: 1H nuclear magnetic resonance; Agar; Agar-water gel; Biological and medical sciences; Diffusion; Dynamic tests; Food industries; Fundamental and applied biological sciences. Psychology; Gels; Macromolecules; Networks; Nuclear magnetic resonance; relaxation rate; restricted diffusion; self-diffusion coefficient; Spectrometers
• ISSN: 0950-5423; 1365-2621
• DOI: 10.1111/j.1365-2621.2010.02448.x

The aim of this work was to determine whether the decreased motion of water in agar gels (2.5-12.5% agar) resulted not only from the chemical interaction of the water molecules with the agar macromolecules but also from obstruction by the gel networks. Relaxation experiments were conducted using a 500‐MHz nuclear magnetic resonance (NMR) spectrometer. Diffusion experiments were conducted using a 23‐MHz NMR spectrometer with diffusion times ranging between 15 and 200 ms and a 500‐MHz NMR spectrometer with a fixed diffusion time of 10 ms. This study shows that the interaction of water with hydroxyl groups of agar macromolecules resulted in faster relaxation and slower self‐diffusion of water. The time‐dependent self‐diffusion coefficient of water provides clear evidence of the obstructive effects of the agar gel network on diffusion. This work is the first report on restricted diffusion of water in agar gel systems.