Cereal Chem. 73 (6):736-743 |
Analytical Techniques and Instrumentation
Proton Relaxation of Starch and Gluten by Solid-State Nuclear Magnetic Resonance Spectroscopy.
S. Li (1), L. C. Dickinson (2), and P. Chinachoti (1,3). (1) Department of Food Science, University of Massachusetts, Amherst, MA 01003. (2) Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003. (3) Corresponding author. E-mail: <email@example.com> Accepted July 20, 1996. Copyright 1996 by the American Association of Cereal Chemists, Inc.
Proton rotating frame relaxation times [T(1 rho)(H)] were used to characterize the molecular dynamics and structural homogeneity in waxy corn starch, wheat gluten, and mixtures of both. Single-phase relaxation of T(1 rho)(H) was found in native starch, indicating a relatively small dimension of structural heterogeneity in terms of spin-diffusion. Heating of the starch samples decreased the T(1 rho)(H) to 3.2-3.4 msec, as compared to raw starch samples at 5.3-6.2 msec, possibly due to the presence of more amorphous domains. The native wheat gluten displayed a slightly inhomogeneous T(1 rho)(H) of 4.9-6.3 msec, suggesting the presence of a structural inhomogeneity, different from that of native waxy corn starch. Heating of gluten decreased the T(1 rho)(H), which was also dependent on moisture. When mixed at a 1:1 starch-to-gluten ratio and heated, the T(1 rho)(H) associated with the gluten were similar to those for pure gluten at 20% moisture content (mc). However, when dried to 2% mc, the gluten T(1 rho)(H) increased to 9.3-9.6 msec. The T(1 rho)(H) values for starch in the mixture were slightly increased to 5.7 msec. The different T(1 rho)(H) values for starch and gluten suggested a limited miscibility of the two components. Compared to starch, gluten T(1 rho)(H) was far more sensitive to moisture content.