Birthe Møller Jespersen

Molecular structure of large-scale extracted β-glucan from barley and oat: Identification of a significantly changed block structure in a high β-glucan barley mutant

Health effects of β-glucan are typically related to dose, size and viscosity without taking the specific molecular structure into account. High β-glucan mutant barley, mother barley and oat β-glucans were large-scale extracted by comparable protocols using hot water, enzyme assisted hydrolysis and ethanol precipitation leading to similar molecular masses (200-300kDa). Multivariate data analysis on all compositional, structural and functional features demonstrated that the main variance among the samples was primarily explained by block structural differences as determined by HPSEC-PAD. In particular the barley high β-glucan mutant proved to exhibit a unique block structure with DP3 and DP4 contributions of: 78.9% and 16.7% as compared to the barley mother (72.1% and 21.4%) and oat (66.1% and 29.1%). This unique block structure was further confirmed by the (1)H NMR determination of the β-1,4 to β-1,3 linkage ratio. Low solubility of the barley samples was potentially an effect of substructures consisting of longer repetitive cellotriosyl sequences. FT-Raman and NMR spectroscopy were useful in measuring sample impurities of α-glucans and prediction of β-linkage characteristics.

Influence of malt roasting on the oxidative stability of sweet wort.

Influence of malt roasting on the oxidative stability of sweet wort was evaluated based on radical intensity, volatile profile, content of transition metals (Fe and Cu) and thiols. Malt roasting had a large influence on the oxidative stability of sweet wort. Light sweet worts were more stable with low radical intensity, low Fe content, and ability to retain volatile compounds when heated. At mild roasting, the Fe content in the wort increased but remained close to constant with further roasting. Dark sweet worts were less stable with high radical intensities, high Fe content, and a decreased ability to retain volatiles. Results suggested that the Maillard reaction compounds formed during the roasting of malt are prooxidants in sweet wort. A thiol-removing capacity was observed in sweet wort, and it was gradually inhibited by malt roasting. It is possibly caused by thiol oxidizing enzymes present in the fresh malt.

Extracted Oat and Barley β-Glucans Do Not Affect Cholesterol Metabolism in Young Healthy Adults

β-Glucans are known to exhibit hypocholesterolemic effects. Increased intestinal viscosity is thought to be crucial for cholesterol lowering. It is suggested that concentration, molecular mass, and structure, including the ratio of (1→3) to (1→4) glucan bonds in the molecule, are of importance for β-glucan functionality. This study investigated the effects of 3 different β-glucan sources, incorporated into a beverage and yogurt, on blood lipids and fecal endpoints. Fourteen participants completed this randomized, crossover, single-blinded study with four 3-wk periods: control and 3.3 g/d oat, barley, and barley mutant β-glucans of similar molecular mass. Before and after each period, fasting and postprandial blood samples were drawn and 3-d fecal samples were collected. Treatment did not affect changes in total, LDL, and HDL cholesterol compared with control; however, consumption of 3.3 g/d of oat β-glucans for 3 wk resulted in greater decreases in total (-0.29 ± 0.09 mmol/L, P < 0.01), LDL (-0.23 ± 0.07 mmol/L, P < 0.01), and HDL (-0.05 ± 0.03 mmol/L, P < 0.05) cholesterol compared with baseline. Changes in LDL in the β-glucan treatments were not related to β-glucan structure (cellotriosyl:cellotetraosyl). Decreases in fasting triacylglycerol were substantially greater after oat β-glucan treatment compared with control (P = 0.03). Fecal dry and wet weight, stool frequency, fecal pH, and energy excretion were unaffected. The results do not fully support the hypocholesterolemic effects by differently structured oat and barley β-glucans. However, substantial differences compared with baseline suggest a potential for oat β-glucan, presumably due to its higher solubility and viscosity. This underlines the importance of elusive structural β-glucan features for beneficial physiologic effects.

Comprehensive and Comparative Metabolomic Profiling of Wheat, Barley, Oat and Rye Using Gas Chromatography-Mass Spectrometry and Advanced Chemometrics

Beyond the main bulk components of cereals such as the polysaccharides and proteins, lower concentration secondary metabolites largely contribute to the nutritional value. This paper outlines a comprehensive protocol for GC-MS metabolomic profiling of phenolics and organic acids in grains, the performance of which is demonstrated through a comparison of the metabolite profiles of the main northern European cereal crops: wheat, barley, oat and rye. Phenolics and organic acids were extracted using acidic hydrolysis, trimethylsilylated using a new method based on trimethylsilyl cyanide and analyzed by GC-MS. In order to extract pure metabolite peaks, the raw chromatographic data were processed by a multi-way decomposition method, Parallel Factor Analysis 2. This approach lead to the semi-quantitative detection of a total of 247 analytes, out of which 89 were identified based on RI and EI-MS library match. The cereal metabolome included 32 phenolics, 30 organic acids, 10 fatty acids, 11 carbohydrates and 6 sterols. The metabolome of the four cereals were compared in detail, including low concentration phenolics and organic acids. Rye and oat displayed higher total concentration of phenolic acids, but ferulic, caffeic and sinapinic acids and their esters were found to be the main phenolics in all four cereals. Compared to the previously reported methods, the outlined protocol provided an efficient and high throughput analysis of the cereal metabolome and the acidic hydrolysis improved the detection of conjugated phenolics.

Influence of Barley Varieties on Wort Quality and Performance

Wort from the barley varieties (Hordeum vulgare) Pallas, Fero, and Archer grown on the same location were investigated for their influence on oxidative stability and volatile profile during wort processing. Barley varieties had a small influence on radical formation, thiol-removing capacity, and volatile profile. Wort boiling with and without hops had a large influence on these same parameters. Potentially antioxidative thiols were oxidized in sweet wort, but reduction of thiols using tris(2-carboxyethyl)phosphine hydrochloride revealed that Archer wort had a significantly larger content of total thiols than Pallas and Fero. Oxidized thiols resulted in gel proteins and longer filtration time for Archer wort. Our study shows that wort processing to a large extent will eliminate variations in volatile profile and thiol levels in wort which otherwise might arise from different barley varieties.

Cereals and Cereal Products

Near-infrared (NIR) spectroscopy technology is an extremely successful tool in the cereal industry, allowing fast screening methods for the prediction of specific analytes. NIR spectroscopy analyses make quality control instant and move it from the laboratory to the production line. This chapter presents two NIR spectroscopy instruments, one for NIR reflectance on flour and one for near-infrared transmittance (NIT) transmission on whole seeds. It is essential in NIR spectroscopy to explore the sequential information on chemical bonds and components given in local bands in the spectra in order to ensure the reliable results. Interval partial least squares regression (iPLS) at different intervals (5–35 nm) is employed because of a graphic interface that is especially useful in visualizing the “hot spots” in collection of spectra for the highest correlation and lowest error. NIT and NIR reflectance spectrometers are widely used in the industry to measure moisture, protein, starch, and fiber content in whole maize, and in maize products. NIR spectroscopy prediction models are available for the estimation of extractable starch for the wet milling industry and for predicting true density, seed breakage susceptibility, and kernel density in maize. A modified least squares regression analysis of NIR spectroscopy has been employed to check the authenticity of Korean grown rice versus imported rice for short and medium long grains.

Variation of volatile compounds among wheat varieties and landraces

Analysis of volatile compounds was performed on 81 wheat varieties and landraces, grown under controlled greenhouse conditions, in order to investigate the possibility of differentiating wheat varieties according to their volatile compound profiles. Volatile compounds from wheat samples were extracted by dynamic headspace extraction and analysed by gas chromatography-mass spectrometry. Seventy-two volatile compounds were identified in the wheat samples. Multivariate analysis of the data showed a large diversity in volatile profiles between samples. Differences occurred between samples from Austria compared to British, French and Danish varieties. Landraces were distinguishable from modern varieties and they were characterised by higher averaged peak areas for esters, alcohols, and some furans. Modern varieties were characterised by higher averaged peak areas for terpenes, pyrazines and straight-chained aldehydes. Differences in volatile profiles are demonstrated between wheat samples for the first time, based on variety. These results are significant to plant breeders and commercial users of wheat.

A Quantitative Structure−Property Relationship Study of the Release of Some Esters and Alcohols from Barley and Oat β-Glucan Matrices

This study investigates the release of selected strawberry flavor compounds from aqueous solutions of two barley and oat beta-glucan products at concentrations of 5, 10, and 15% (w/w). The flavor release of 12 esters and 3 alcohols was measured by dynamic headspace GC-MS. For each compound the ratio of the flavor release from the beta-glucan solution to the release from aqueous solution, A(rel), was recorded. In general, esters were retained in the beta-glucan matrices in a mass-dependent manner where heavier molecules were retained more. A(rel) for alcohols was found to be significantly larger than for the esters. Whereas A(rel) values for esters were always below unity, this parameter was above unity for alcohols in some preparations of beta-glucan. This implies that relative to esters, alcohols were rejected from some matrices. An increase in the concentration of the beta-glucan products was associated with an increased retention of alcohols and esters. For solutions of oat and barley beta-glucan products at the same concentration, the oat product retained the flavor compounds more strongly. This difference was more pronounced at low concentrations of the beta-glucan products. To investigate the potential of a multivariate approach for the analysis of the flavor release from beta-glucan products, partial least-squares regression was employed on a large selection of calculated molecular descriptors, yielding simple QSPR models capable of explaining the variation in A(rel). The robustness of the QSPR models was verified by cross-validation and permutation tests. The results indicate that the multivariate modeling approach might provide a useful tool for the investigation of flavor release systems similar to those studied here.

Near-Infrared Spectroscopy Using a Supercontinuum Laser: Application to Long Wavelength Transmission Spectra of Barley Endosperm and Oil

The supercontinuum laser is a new type of light source, which combines the collimation and intensity of a laser with the broad spectral region of a lamp. Using such a source therefore makes it possible to focus the light onto small sample areas without losing intensity and thus facilitate either rapid or high-intensity measurements. Single seed transmission analysis in the long wavelength (LW) near-infrared (NIR) region is one area that might benefit from a brighter light source such as the supercontinuum laser. This study is aimed at building an experimental spectrometer consisting of a supercontinuum laser source and a dispersive monochromator in order to investigate its capability to measure the barley endosperm using transmission experiments in the LW NIR region. So far, barley and wheat seeds have only been studied using NIR transmission in the short wavelength region up to 1100 nm. However, the region in the range of 2260–2380 nm has previously shown to be particularly useful in differentiating barley phenotypes using NIR spectroscopy in reflectance mode. In the present study, 350 seeds (consisting of 70 seeds from each of five barley genotypes) in 1 mm slices were measured by NIR transmission in the range of 2235–2381 nm and oils from the same five barley genotypes were measured in a cuvette with a 1 mm path length in the range of 2003–2497 nm. The spectra of the barley seeds could be classified according to genotypes by principal component analysis; and spectral covariances with reference analysis of moisture, β-glucan, starch, protein and lipid were established. The spectral variations of the barley oils were compared to the fatty acid compositions as measured using gas chromotography–mass spectrometry (GC-MS).

From metabolome to phenotype: GC-MS metabolomics of developing mutant barley seeds reveals effects of growth, temperature and genotype

The development of crop varieties tolerant to growth temperature fluctuations and improved nutritional value is crucial due to climate change and global population growth. This study investigated the metabolite patterns of developing barley seed as a function of genotype and growth temperature for ideal vegetable protein production and for augmented β-glucan production. Seeds from three barley lines (Bomi, lys3.a and lys5.f) were sampled eight times during grain filling and analysed for metabolites using gas chromatography-mass spectrometry (GC-MS). The lys3.a mutation disrupts a regulator gene, causing an increase in proteins rich in the essential amino acid lysine, while lys5.f carries a mutation in an ADP-glucose transporter gene leading to a significant increase in production of mixed-linkage β-glucan at the expense of α-glucan. Unique metabolic patterns associated with the tricarboxylic acid cycle, shikimate-phenylpropanoid pathway, mevalonate, lipid and carbohydrate metabolism were observed for the barley mutants, whereas growth temperature primarily affected shikimate-phenylpropanoid and lipid metabolism. The study applied recently developed GC-MS metabolomics methods and demonstrated their successful application to link genetic and environmental factors with the seed phenotype of unique and agro-economically important barley models for optimal vegetable protein and dietary fibre production.