Proton relaxation of starch and gluten by solid-state nuclear magnetic resonance spectroscopy.
1996
Li S. | Dickinson L.C. | Chinachoti P.
Proton rotating frame relaxation times [T1p(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 T1p(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 T1p(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 T1p(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 T1p(H), which was also dependent on moisture. When mixed at a 1:1 starch-to-gluten ratio and heated, the T1p(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 T1p(H) increased to 9.3-9.6 msec. The T1p(H) values for starch in the mixture were slightly increased to 5.7 msec. The different T1p(H) values for starch and gluten suggested a limited miscibility of the two components. Compared to starch, gluten T1p(H) was far more sensitive to moisture content.
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