Bulk Carbohydrate Grain Filling of Barley β‐Glucan Mutants Studied by ¹H HR MAS NMR

Abstract

Cereal Chem. 85(4):571-577Temporal and genotypic differences in bulk carbohydrate accumulation in three barley genotypes differing in the content of mixed linkage β-(1→3),(1→4)-D-glucan (β-glucan) and starch were investigated using proton high-resolution, magic angle spinning, nuclear magnetic resonance ( 1 H HR MAS NMR) during grain filling. For the first time, 1 H HR MAS NMR spectra of flour from immature barley seeds are analyzed. Spectral assignments are made using two-dimensional (2D) NMR methods. Both αand β-glucan biosynthesis were characterized by inspection of the spectra as well as by calibration to the reference methods for starch and β-glucan content. Starch was quantified with very good calibrations to the α-(1→4) peak (5.29-5.40 ppm) and the region 3.67-3.83 ppm covering starch glycopyranosidic protons from H5 and H6. In contrast, the spectral inspection of the β-anomeric region 4.45-4.85 ppm showed unexpected lack of intensity in the high β-glucan mutant lys5f at seed maturity, resulting in poor calibration to reference β-glucan content. We hypothesize that the lack of β-glucan signal in lys5f indicates partial immobilization of the β-glucan that appears to be either genotypic dependent or water/β-glucan ratio dependent.

Characterization of marama bean (Tylosema esculentum) by comparative spectroscopy: NMR, FT-Raman, FT-IR and NIR

“…It is for example characteristic that the marama bean does not contain measurable amounts of abundant plant carbohydrate compounds such as β-glucans (no anomeric signal in the β-anomeric region 4.45-4.85 ppm), glucose (no anomeric signals at 4.64 (β) and 5.23 (α) ppm) and starch (no anomeric α-(1 → 4) starch proton at 5.36 ppm) (Seefeldt, Larsen, Viereck, Wollenweber, & Engelsen, 2008). The absence of starch which was confirmed in the wetchemistry study by Holse et al (2010) is in contrast to other legumes where starch is the most abundant carbohydrate (22-45%) (Hoover & Sosulski, 1991).…”

Comparative spectroscopic and rheological studies on crude and purified soluble barley and oat β-glucan preparations

“…As an example, Seefeldt et al (2008) classified barley flours with regard to β-glucan content by FT-IR measurements.…”

“…Nuclear magnetic resonance (NMR) spectroscopy has been widely used for the overall structure and linkage sequence analysis of cereal β-glucans (Cui, Wood, Blackwell, & Nikiforuk, 2000;Johansson, Tuomainen, Ylinen, Ekholm, & Virkki, 2004;Lazaridou et al, 2004;Morgan, Roberts, Tendler, Davies, & Williams, 1999;Petersen, Krah, Duus, & Thomsen, 2000;Roubroeks, Mastromauro, Andersson, Christensen, & Aman, 2000;Seefeldt, Larsen, Viereck, Wollenweber, & Engelsen, 2008;Wood et al, 1994). Liquid state 1 H NMR allows estimation of the ratio of β-(1 → 3) to β-(1→ 4) linkages in the β-glucan polymers as well as the residual constituents present in the β-glucan extract.…”

“…Both IR and Raman spectroscopic methods are rapid, sensitive and able to distinguish the α-and β-conformations of saccharides (Cael, Koenig, & Blackwel, 1974;Engelsen & Norgaard, 1996;Kacurakova, Capek, Sasinkova, Wellner, & Ebringerova, 2000). In contrast to chemical, chromatographic, or mass spectrometric methods, spectroscopic methods require no chemical extraction as the intact sample matrix is examined which is an advantage when analyzing delicate and complex biological samples (Seefeldt et al, 2008;Seefeldt et al, 2009).…”

High-resolution magic angle spinning nuclear magnetic resonance in foodstuff analysis

“…The evaluation of bulk-carbohydrate accumulation and lipid deposition during grain filling of three barley (Hordeum vulgare) genotypes by HR-MAS NMR spectra clearly revealed differences on the chemical composition between early, middle and late grain filling [62,63]. The mutant lys5f (characterized by high content of β-glucan) showed a distinct carbohydrate pattern compared to the control Cork and the mutant lys3a (characterized by low β-glucan content).…”