Roger Andersson

High-performance liquid chromatographic analysis of secoisolariciresinol diglucoside and hydroxycinnamic acid glucosides in flaxseed by alkaline extraction

A HPLC method was developed for the analysis of secoisolariciresinol diglucoside (SDG) and hydroxycinnamic acid glucosides in milled defatted flaxseed flour. Direct extraction by 1 M NaOH for 1 h at 20 degrees C resulted in a higher yield than that obtained by hydrolysis of alcoholic extracts. An internal standard, o-coumaric acid, was used and the method was found to be easy, fast, and with good repeatability. On dry matter basis, different samples of flaxseeds varied considerably in their content of (+)-SDG (11.9-25.9 mg/g), (-)-SDG (2.2-5.0 mg/g), p-coumaric acid glucoside (1.2-8.5 mg/g), and ferulic acid glucoside (1.6-5.0 mg/g).

Molecular weight distribution of β-glucan in oat-based foods

ABSTRACT Oats, different oat fractions as well as experimental and commercial oat-based foods, were extracted with hot water containing thermostable α-amylase. Average molecular weight and molecular weight distributions of β-glucan in extracts were analyzed with a calibrated high-performance size-exclusion chromatography system with Calcofluor detection, specific for the β-glucan. Oats, rolled oats, oat bran, and oat bran concentrates all had high Calcofluor average molecular weights (206 × 104 to 230 × 104 g/mol) and essentially monomodal distributions. Of the oat-containing experimental foods, extruded flakes, macaroni, and muffins all had high average molecular weights. Pasteurized apple juice, fresh pasta, and teacake, on the other hand, contained degraded β-glucan. Calcofluor average molecular weights varied from 24 × 104 to 167 × 104 g/mol in different types of oat bran-based breads baked with almost the same ingredients. Large particle size of the bran and short fermentation time limited the β-gluc...

Quantitative analysis of amylopectin unit chains by means of high-performance anion-exchange chromatography with pulsed amperometric detection

Abstract High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC–PAD) is a widely used technique to study the chain length distribution of amylopectin. The chromatograms, however, do not directly reflect this distribution, since the PAD response changes with the degree of polymerization. In this study, waxy maize starch was debranched and fractionated on a Bio-Gel P-6 column and the response factors for maltosaccharides with DP 3–65 were determined. The detector response per μg glucan chains was shown to decrease considerably for DP 3–7 while the curve leveled out for DP larger than 15.

Determination of β-Glucan Molecular Weight Using SEC with Calcofluor Detection in Cereal Extracts

ABSTRACT A high-performance size-exclusion chromatography system (HPSEC) was set up with detection based on the specific binding of Calcofluor to β-glucan for determination of amount and molecular weight of β-glucan in different cereal extracts. To calibrate the HPSEC system, a purified β-glucan was fractionated into narrow molecular weight ranges and the average molecular weight was determined before analysis on the HPSEC system. The detector response was similar for β-glucans from oats and barley and appeared to be independent of molecular weight. Four different methods for extraction of β-glucan from different cereal products were tested: two alkaline, one with hot water and added α-amylase, and one with water and added xylanase. Inactivation of endogenous β-glucanase was crucial for the stability of the extracts, even when extracting at high temperature or pH. Yields varied widely between the different extraction methods but average molecular weight and molecular weight distribution were similar. Extr...

Content and Molecular-Weight Distribution of Dietary Fiber Components in Whole-Grain Rye Flour and Bread

Content of dietary fiber and dietary fiber components in whole-grain rye (n = 18) were analyzed. The average total content, when fructan was included, was for dietary fiber 19.9% (range of 18.7-22.2%) and for extractable dietary fiber 7.4% (range of 6.9-7.9%). Arabinoxylan was the main dietary fiber component, with an average total content of 8.6%, followed by fructan (4.1%). During baking of whole-grain rye bread, only small changes in total content of arabinoxylan, arabinogalactan, and beta-glucan occurred, while the content of resistant starch increased and the content of fructan decreased in a baking-method-dependent manner. The molecular-weight distribution of extractable arabinoxylan in the flour was analyzed with a new method and ranged from 4 x 10(4) to 9 x 10(6) g/mol, with a weight average molecular weight of about 2 x 10(6) g/mol. During crisp bread making, only a limited degradation of arabinoxylan molecular weight was detected, while a notable degradation was observed in sour-dough bread. The molecular weight of extractable beta-glucan in the whole-grain rye flour ranged from 10(4) to 5 x 10(6) g/mol, with a weight average molecular weight of 0.97 x 10(6) g/mol. During bread making, the molecular weight of the beta-glucan was substantially degraded.

An oligomer from flaxseed composed of secoisolariciresinoldiglucoside and 3-hydroxy-3-methyl glutaric acid residues.

A straight-chain oligomeric structure composed of five secoisolariciresinoldiglucoside (SDG) residues interconnected by four 3-hydroxy-3-methyl glutaric acid (HMGA) residues (molecular weight ca. 4000 Da) was assigned to the main lignan of flaxseed on the basis of nuclear magnetic resonance spectroscopy (NMR).

Polymeric fractions containing phenol glucosides in flaxseed

Abstract Extract rich in phenolic compounds was obtained from flaxseed with 1,4-dioxane:ethanol (1:1, v/v). This extract (whole polymer) was fractionated by solid-phase extraction into three “polymeric” fractions of comparable polarity. HPLC analyses of the base hydrolysates of the three polymeric fractions showed that they contain the same UV-absorbing components, though at different levels and all contained substantial amounts of a lignan, secoisolariciresinoldiglucoside (SDG). Fractionation of the base hydrolysates by column chromatography, followed by high performance liquid chromatography (HPLC) yielded two pure hydroxycinnamic acid derivatives; 4-O-β- d -glucopyranosyl-p-coumaric acid and 4-O-β- d -glucopyranosylferulic acid, whose structures were identified by nuclear magnetic resonance spectroscopy (NMR). NMR analysis showed all three polymeric fractions to have phenolic and aliphatic components and, in line with HPLC, suggested some structural variations between these fractions. The results of this study suggest that the glucosylated phenolic compounds of flaxseed exist in polymeric structure(s) containing ester linkages.

Isolation and chemical characterization of water-soluble mixed-linked β-glucans and arabinoxylans in oat milling fractions

Abstract Dehulled oats were separated into fractions of bran, outer starchy endosperm and inner starchy endosperm, after and without prior steam-flaking. The bran had significantly higher contents of protein, fat, ash and dietary fibre and lower content of starch than the endosperm fractions. An improved procedure was developed for the isolation of pure (92–99%) water-soluble mixed-linked (1–3), (1–4)-β- d -glucans, involving fat extraction, enzymatic removal of starch and protein, and subsequent precipitation of water-soluble polysaccharides with 60% aqueous ethanol and 20% (w/v) aqueous (NH 4 ) 2 SO 4 . High-field 13 C-NMR analysis of the isolated mixed-linked β-glucans showed the polysaccharide structure to be similar in all oat fractions. The proportion of isolated (1–3)-β-linkages in the polymer was on average 28·3% (SD 0·8) according to 1 H-NMR analysis. 1 H-NMR also showed that water-soluble oat arabinoxylans were composed of a main chain of (1–4)-linked β- d -xylopyranosyl residues, substituted by terminal α- l -arabinofuranosyl residues predominantly at O-3 but also at both O-2 and O-3. The proportion of xylose residues substituted solely at O-3 was 35% higher in bran than in endosperm arabinoxylans.

Rye kernel breakfast increases satiety in the afternoon - an effect of food structure

BackgroundThe structure of whole grain cereals is maintained to varying degrees during processing and preparation of foods. Food structure can influence metabolism, including perceived hunger and satiety. A diet that enhances satiety per calorie may help to prevent excessive calorie intake. The objective of this work was to compare subjective appetite ratings after consumption of intact and milled rye kernels.MethodsTwo studies were performed using a randomized, cross-over design. Ratings for appetite (hunger, satiety and desire to eat) were registered during an 8-h period after consumption of whole and milled rye kernels prepared as breads (study 1, n = 24) and porridges (study 2, n = 20). Sifted wheat bread was used as reference in both study parts and the products were eaten in iso-caloric portions with standardized additional breakfast foods. Breads and porridges were analyzed to determine whether structure (whole vs. milled kernels) effected dietary fibre content and composition after preparation of the products. Statistical evaluation of the appetite ratings after intake of the different breakfasts was done by paired t-tests for morning and afternoon ratings separately, with subjects as random effect and type of breakfast and time points as fixed effects.ResultsAll rye breakfasts resulted in higher satiety ratings in the morning and afternoon compared with the iso-caloric reference breakfast with sifted wheat bread. Rye bread with milled or whole kernels affected appetite equally, so no effect of structure was observed. In contrast, after consumption of the rye kernel breakfast, satiety was increased and hunger suppressed in the afternoon compared with the milled rye kernel porridge breakfast. This effect could be related to structural differences alone, because the products were equal in nutritional content including dietary fibre content and composition.ConclusionsThe study demonstrates that small changes in diet composition such as cereal grain structure have the potential to effect feelings of hunger and satiety.Trial registrationThis trial was registered at clinicaltrials.gov as NCT01042418.

Chemical and physical characteristics of different barley samples

Eight different barleys, including covered and naked samples containing low, normal and high amylose starches as well as a sample with low starch and high β-glucan content and a malting barley, were examined both from a chemical and physical perspective. In the chemical characterisation of the samples, analyses of nutrients were performed, while in the physical characterisation, weight of individual kernels, sieving fractions, bulk density, terminal velocity by pneumatic classification and parameters from a Single Kernel Characterization System (SKCS) were analysed. Results were evaluated by principal component analysis (PCA). The major trend found was that hull content and endosperm composition varied independently of each other. Constituents found mainly in the hull were positively correlated with each other, but negatively with bulk density and the 95% quantile of terminal velocity. There was a positive correlation between average value and standard deviation of grain mass, fat and starchy endosperm components such as extractable dietary fibre residues and β-glucan. The latter variables were negatively correlated to β-glucan extractability.