Factors Affecting the Collection and Fitting of Nuclear Magnetic Cross-Relaxation Spectroscopy Data with Application to Waxy Corn Starch

Abstract

An examination of the methods for nuclear magnetic cross-relaxation spectroscopy (CRS) data collection and analysis was conducted using water and an aqueous waxy corn starch suspension to better perform and interpret the results obtained using CRS. The CRS data collection properties evaluated were the time to achieve steady state saturation, the direct saturation of liquid protons, generation of transverse magnetization, and dependence of the offset frequency and radio frequency (RF) field strength of longitudinal relaxation in the presence of RF saturation. Effects were evaluated for variations of input values of RF saturation field strength, apparent cross-relaxation rate, and solid longitudinal relaxation rate on the results for solid content and solid internal mobility from fitting NMR data to modified theoretical expressions. Discrepancies between fitted and stoichiometric values for the solid to liquid proton ratio were investigated. The fitting procedure used a Gaussian line shape for RF saturation of the solid-like spin system and a Lorentzian line shape for RF saturation of the liquid-spin system. Conditions under which acceptable results can be obtained with limited data sets are discussed.

Analysis of the Retrogradation of Low Starch Concentration Gels Using Differential Scanning Calorimetry, Rheology, and Nuclear Magnetic Resonance Spectroscopy

“…However, instead of using the intensity of each peak as previous studies have done ( − ), the baseline-corrected integrated area of each peak was used because the water peak broadened depending on the conditions used for the experiment, possibly due to inhomogeneities in the sample and instrument. For more information about CRS, see the following references ( − ).…”

“…Proton ( 1 H) CRS. A Varian UNITY INOVA 600 NMR spectrometer equipped with a 5 mm HCN triple axis gradient probe was used to (15). Phase cycling can be used to remove any residual transverse magnetization following off-resonance irradiation.…”