Proton, Deuterium, and Oxygen-17 Nuclear Magnetic Resonance Relaxation Studies of Lactose and Sucrose-Water Systems
Journal
Journal of Agricultural and Food Chemistry
Journal Volume
39
Journal Volume
39
Journal Issue
11
Journal Issue
11
Pages
1921-1926
Start Page
1921
End Page
1926
ISSN
00218561
Date Issued
1991-11-01
Author(s)
Abstract
Comparison of the 1H, 2H, and 17O nuclear magnetic resonance (NMR) transverse relaxation rate (R2) of water associated with lactose- and sucrose-H2O (or D2O) systems was studied as a function of pH and sugar concentration. The 3.6 g of lactose/mol of H2O 1H NMR R2 measurements varied greatly as a function of pH, reaching a maximum near neutral pH, whereas the 2H NMR R2 measurements varied only slightly as a function of pH. The difference in the contribution of chemical exchange to the transverse relaxation experienced by the 1H and 2H nuclei was proposed to explain the observed variation between the two nuclei. For all three nuclei, ΔR2 increased with increasing sugar concentration. However, the magnitude of these increases, as well as the trends in ΔR2 vs concentration for each nucleus and sugar type, varied widely. Comparison of the 1H, 2H, and 1H-decoupled 17O NMR R2 values, on a normalized basis (ΔR2/R2F), suggested that only the 17O monitors directly the water mobility in the two sugar-H2O (or D2O) systems studied here.
Type
journal article