Author:

Keywords:

Agriculture, Agriculture, Multidisciplinary, C-13 NMR, Chemistry, Chemistry, Applied, COMPONENTS, controlled hydration, ENDOSPERM, EXTRACTABLE ARABINOXYLAN, FEATURES, FERULIC ACID, Food Science & Technology, H-1-NMR SPECTROSCOPY, Life Sciences & Biomedicine, OLIGOSACCHARIDES, ORGANIZATION, Physical Sciences, POLYSACCHARIDES, RYE, Science & Technology, solid-state NMR, water-unextractable arabinoxylan, wheat flour, 13C NMR, Arabinose, Cell Wall, Flour, Magnetic Resonance Spectroscopy, Triticum, Water, Xylans, Xylose, METH/14/04#53291607, I001321N#56241633, 03 Chemical Sciences, 07 Agricultural and Veterinary Sciences, 09 Engineering, Food Science, 30 Agricultural, veterinary and food sciences, 34 Chemical sciences, 40 Engineering

Abstract:

To enable its structural characterization by nuclear magnetic resonance (NMR) spectroscopy, the native structure of cereal water-unextractable arabinoxylan (WU-AX) is typically disrupted by alkali or enzymatic treatments. Here, WU-AX in the wheat flour unextractable cell wall material (UCWM) containing 40.9% ± 1.5 arabinoxylan with an arabinose-to-xylose ratio of 0.62 ± 0.04 was characterized by high-resolution solid-state NMR without disrupting its native structure. Hydration of the UCWM (1.7 mg H2O/mg UCWM) in combination with specific optimizations in the NMR methodology enabled analysis by solid-state 13C NMR with magic angle spinning and 1H high-power decoupling (13C HPDEC MAS NMR) which provided sufficiently high resolution to allow for carbon atom assignments. Spectral resonances of C-1 from arabinose and xylose residues of WU-AX were here assigned to the solid state. The proportions of un-, mono-, and di-substituted xyloses were 59.2, 19.5, and 21.2%, respectively. 13C HPDEC MAS NMR showed the presence of solid-state fractions with different mobilities in the UCWM. This study presents the first solid-state NMR spectrum of wheat WU-AX with sufficient resolution to enable assignment without prior WU-AX solubilization.