Structure and Dynamics of Flour by Solid State NMR:  Effects of Hydration and Wheat Aging

Abstract

The effects of accelerated aging of wheat seeds on structural and dynamic properties of dry and hydrated (ca 10 wt % H(2)O) flour at a molecular level were investigated by several high and low resolution solid-state NMR techniques. Identification and characterization of domains with different mobility was performed by (13)C direct excitation (DE) and cross-polarization (CP) magic angle spinning (MAS), as well as by (1)H static and MAS experiments. (1)H spin-lattice relaxation times (T(1) and T(1)(rho)) measurements were carried out to investigate molecular motions in different frequency ranges. Experimental data show that the main components of flour (starch and gluten proteins) are in a glassy phase, whereas the mobile fraction is constituted by lipids and, in hydrated samples, absorbed water. A lower proportion of rigid domains, as well as an increased dynamics of all flour components are observed after both seeds aging and flour hydration. Linear average dimensions between 20 and 200 A are estimated for water domains in hydrated samples.

Solid State NMR Investigation of the Molecular Dynamics of Cocoon Silks Produced by Different Bombyx mori (Lepidoptera) Strains

“…27,28 The w E2 values for naturally hydrated samples give a quantitative estimate of the percentage of water protons present in these cocoons. In Chinese and Japanese cocoons, this value is about 10.5%, whereas it is about a half for Turkish cocoons: this is consistent with the different behavior observed for the three strains in 13 C CP-MAS spectra, discussed in the previous section, suggesting that the higher amount of water present in naturally hydrated Japanese and Chinese cocoons slightly modifies the CP dynamics of the 13 C Gly peak.…”

Molecular Properties of Flurbiprofen and its Solid Dispersions with Eudragit RL100 Studied by High- and Low-Resolution Solid-State Nuclear Magnetic Resonance

“…This process, known as spin diffusion, tends to average the relaxation times of the different protons in a sample to a single value. This average is complete in the case of a sample homogeneous on a 100 Å scale, while different relaxation times can be measured for protons belonging to different domains when these domains have average linear dimensions greater than 100 Å (25).…”

Comprehensive Multiphase NMR Spectroscopy of Intact 13C-Labeled Seeds

“…Other carbohydrate signals, mainly starch, are prominent in all spectra and come from the starchy endosperm of wheat seeds 33 and from the seed coat. 34 Next to TAG, starch and Higher plants produce starches, which are a critical nutritional source for humans.…”