| 1. |
- Asp, Nils Georg, et al.
(författare)
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Physiological effects of cereal dietary fibre
- 1993
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 21:2-3, s. 183-187
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Tidskriftsartikel (refereegranskat)abstract
- Cereal dietary fibre constitutes about half of the total fibre intake in Sweden. The amount of fibre available is 21 g/person/day or 1·75 g/MJ. Increased faecal bulk and shortening of intestinal transit time are well-documented effects, that are inversely proportional to the fermentability of the dietary fibre. Wheat bran, oat husks, and corn bran are fibre sources with high bulking effect, whereas fibre from the endosperm of cereals is more extensively fermented. Resistant starch in processed cereals has properties similar to dietary fibre, and must be considered in analysis as well as regarding physiological effects of dietary fibre. Oat groats and oat bran have serum cholesterol lowering effects related to the viscous soluble β-glucans. Rye and barley contain similar levels of viscous soluble fibre but are not as thoroughly investigated. Effects on postprandial glucose and insulin levels are also partly related to viscous soluble dietary fibre, but structural properties in, e.g., whole kernels and pasta products are more important in this respect. Phytate in whole grain flour and bran preparations inhibits iron and zinc absorption in single meal tests. Its role for mineral status in persons consuming a mixed, Western diet remains to be established.
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| 2. |
- Karlson, L, et al.
(författare)
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A rheological investigation of the complex formation between hydrophobically modified ethyl (hydroxy ethyl) cellulose and cyclodextrin
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 50:3, s. 219-226
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Tidskriftsartikel (refereegranskat)abstract
- The thickening effect of a hydrophobically modified polymer in an aqueous solution is dependent on intermolecular hydrophobic associations, and if the polymer concentration is significantly above the overlap concentration also on chain entanglements. In this investigation we have added different cyclodextrins (CD) in order to decouple hydrophobic polymer-polymer associations via inclusion complex formation with the polymer hydrophobic tails. Both size and hydrophobicity of the cavity of the CD-molecules were found to have an effect on the process. In addition, the influence of chemical structure of the polymer hydrophobic tails was investigated. Either a linear C-14-chain or a more bulky nonylphenol group was used. The viscosity as a function of CD-concentration first decreased strongly, and then attained a constant value. At excess CD the viscosity became virtually the same as in a solution of the unmodified parent polymer, provided that complex formation was not sterically bindered. This suggests that all hydrophobic links, originating from the hydrophobic modification process, which influence the theology could be deactivated. On the other hand, with combinations where the complex formation was hindered to a certain degree the initial decrease was less accentuated, and also, the viscosity leveled out at a significantly higher value. In an attempt to rationalize the data a simple model based on the assumption that each complex formed deactivates one theologically active link was used. In combination with the Langmuir adsorption model the number of complexes as a function of CD concentration could be obtained. This model also gave a value of the complex formation constant. Furthermore, in solutions where all hydrophobic links could be deactivated the results from the model suggested that all polymer hydrophobic tails were originally active in forming the network. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Lundqvist, Henrik, et al.
(författare)
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Binding of hexadecyltrimethylammonium bromide to starch polysaccharides. Part 1. Surface tension measurements
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 49:1, s. 43-55
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Tidskriftsartikel (refereegranskat)abstract
- Surface tension measurements were used to characterise the binding of the cationic surfactant hexadecyltrimethylammonium bromide, CTAB, to three starch polysaccharides, amylose from potato, amylopectin from potato and amylopectin from barley. Surface tension measurements were used according to the axisymmetric drop shape analysis. ADSA, to determine the concentration of free CTAB monomers during consecutive addition of CTAB to the polysaccharide solutions, The interaction between the starch polysaccharides and CTAB was studied at three starch concentrations. 0.1, 0.25 and 0.5% (w/w). Binding isotherms were derived from the concentration of free CTAB and the type of binding was determined with Scatchard plots. The binding capacities of CTAB correlated linearly with the polysaccharide concentration but were independent of the type of starch polysaccharide. All three starch polysaccharides were able to bind 33 mmol CTAB per mole glucose units. The binding of CTAB to amylose was cooperative while the binding of CTAB to amylopectin was of Langmuir type.
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| 4. |
- Lundqvist, Henrik, et al.
(författare)
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Binding of hexadecyltrimethylammonium bromide to starch polysaccharides. Part II. Calorimetric study
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 49:2, s. 109-120
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Tidskriftsartikel (refereegranskat)abstract
- Isothermal titration calorimetry was used to study the interaction between hexadecyltrimethylammonium bromide, CTAB, and three starch polysaccharides, amylose from potato, amylopectin from potato and amylopectin from barley. The enthalpy change for consecutive additions of CTAB to starch polysaccharide solutions were measured at 27degreesC. The starch-CTAB interaction enthalpies, DeltaH(f), were calculated by subtracting the enthalpy of micelle dissociation and dilution from the observed heat and relating the interaction enthalpy to the amount of interacting CTAB. The interaction was studied at three polysaccharide concentrations, 0.1, 0.25 and 0.5% w/w. The exothermic interaction enthalpy was constant and quite large in the main part of the concentration range studied for all three-starch polysaccharides. Amylose had an interaction enthalpy of -55 kJ/mol CTAB while the amylopectin samples had an interaction enthalpy of -40 kJ/mol CTAB. Amylopectin and amylose seemed to have a similar interaction with CTAB, the small differences were probably due to the differences in structure between the polysaccharides.
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| 5. |
- Lundqvist, Jon, et al.
(författare)
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Characterization of galactoglucomannan extracted from spruce (Picea abies) by heat-fractionation at different conditions
- 2003
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 51:2, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- Water-soluble hemicelluloses were extracted from spruce chips by microwave heat-fractionation. The galactoglucomannan (GGM) extraction was evaluated on the basis of weight-average molecular weight (MW), yield and carbohydrate composition of the GGM. The MW was determined by size-exclusion chromatography with column calibration using off-line MALDI-MS analysis, and determination of mannan content in the fractions collected. Water impregnated spruce chips were heat-fractionated at three different temperatures (180, 190, and 200oC). The spruce chips were also impregnated in NaOH solutions of different concentrations, and then heat-fractionated at 190oC for 5min. The highest mannan yield (78% based on the amount in the raw material) was obtained from water impregnated spruce chips heat-fractionated at 190oC for 5min (MW of 3800). The highest MW (14,000) was obtained from impregnation with 2% NaOH (190oC, 5min), but the yield of mannan was very low (3%). Impregnation with 0.025% NaOH and heat-fractionation at 190oC for 5min resulted in extraction of GGM with MW of 9500 and a mannan yield of 31%. When the spruce chips were impregnated with =<0.05% NaOH an O-acetyl-galactoglucomannan was extracted, whereas when higher NaOH charges were used in the impregnation, the extracted GGM lacked acetyl groups.
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| 6. |
- Lundqvist, Jon, et al.
(författare)
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Isolation and characterization of galactoglucomannan from spruce (Picea abies)
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 48:1, s. 29-39
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Tidskriftsartikel (refereegranskat)abstract
- Water-soluble hemicelluloses were extracted from spruce chips by microwave heat fractionation. The chips were impregnated with water at different pH values. Screening of heat-fractionation conditions, i.e. impregnation medium, temperature and residence time was performed with the aim to extract O-acetyl-galactoglucomannan. The impregnation and heat fractionation conditions were evaluated on the basis of the yield of dissolved mannan (oligo- and polysaccharides), molecular weight of the carbohydrates and amount of dissolved lignin. Increasing temperature and residence time increases the yield of mannan and decreases the molecular weight of dissolved carbohydrates. For a structural study of the extracted carbohydrates the chips were impregnated with water and treated at 200oC for 2min. Oligo- and polysaccharides were fractionated with preparative size-exclusion chromatography from the filtered extract.The structure of the obtained saccharides in two fractions 8 and 9 was determined by 1H NMR spectroscopy. The polysaccharides in the fractions were O-acetyl-galactoglucomannan with a degree of polymerization ~20 and ~11 for fractions 8 and 9, respectively. The molar ratio for galactose:glucose:mannose was approximately 0.1:1:4. About one-third of the d-mannosyl units are substituted by O-acetyl groups almost equally distributed between C-2 and C-3.
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| 7. |
- Nilsson, G. S., et al.
(författare)
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Microdialysis clean-up and sampling in enzyme-based methods for the characterisation of starch
- 2001
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 46:1, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Microdialysis was used for sampling enzyme hydrolysis products of starch hydrolysed with beta -amylase, pullulanase, and/or isoamylase, to obtain information about the molecular structure of starch. Starches from waxy, normal, and high amylose maize, and from normal and genetically modified potato (amylose deficient) were used, and also commercial potato amyloses. The hydrolysis products were analysed using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Simultaneous sampling and sample clean-up were achieved with microdialysis, thus enabling on-line injection into the liquid chromatographic system. The molecular weight cut-off of the membrane allowed for diffusion of small molecules such as oligosaccharides through the membrane, but hindered large molecules, e.g. enzymes and large polysaccharides, from entering the chromatographic system. With microdialysis sampling, it was possible to investigate the short chain fractions of debranched starch in the presence of amylose without pre-fractionation. The microdialysis-HPAEC-PAD system was also used for determination of the A:B chain ratio and the P-limit value. After P-amylolysis, only liberated maltose diffused through the dialysis membrane, which resulted in on-line sample clean-up from branched P-limit dextrin as well as from the enzyme. The proposed method is fast and easy to handle since clean-up of the hydrolysate is achieved on-line with the chromatographic system. (C) 2001 Elsevier Science Ltd. All rights reserved.
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| 8. |
- Santacruz, S, et al.
(författare)
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Three under-utilised sources of starch from the Andena region in Ecuador. Part II. Rheological characterisation.
- 2003
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 51:1, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic rheological behaviour of Arracacha xanthorriza white carrot), Canna edulis (achira) and Oxalis tuberosa oca) starch gels were studied in strain-sweep mode. The starch was diluted with water to cover particle volume fractions of 1–3. The starch suspensions were heated at 89 8C for 30 min, and their swelling power and amylose leaching were measured. C. edulis showed the highest swelling power and particle rigidity (the elastic modulus, G0, of a starch gel at a particle volume fraction of 1 is defined as rigidity), forming stronger gels than O. tuberosa and A. xanthorriza. Storage of the three starch gels at 4 8C showed that A. xanthorriza formed gels which were stable in G0 and phase angle for three days of storage. C. edulis and O. tuberosa gels kept at the same refrigeration conditions showed a high increase in G0 during the first day of storage. A decrease in pH from 6.5 to 4.0 produced a loss of structure in the three starch gels, as was showed by the reduction of G0. Storage at freezing temperature (220 8C) produced higher changes in G0 than refrigeration conditions. There was a rapid formation of an elastic structure in C. edulis and O. tuberosa starch gels on the first day of storage in both refrigeration and freezing conditions.
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| 9. |
- Santacruz, Stalin, et al.
(författare)
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Three underutilised sources of starch from the Andean region in Ecuador Part 1. Physico-chemical characterisation
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 49:1, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- The physico-chemical aspects of three native Andean starches from Arracacha xanthorriza, Canna edulis and Oxalis tuberosa were investigated. Scanning electron microscopy-investigations showed that granules of A. xanthorriza were the smallest with irregular shape and sizes between 7 and 23 pm, whereas granules of O. tuberosa and C. edulis were both ovally shaped with granular sizes between 20 and 55 mum and 35-101 mum, respectively. All three starches revealed a B-type X-ray diffraction pattern. The gelatinisation behaviour was investigated using differential scanning calorimetry (DSC). The gelatinisation enthalpy was 14.6 J/g of starch for O. tuberosa, 15.7 J/g for C. edulis and 17.6 J/g for A. xanthorriza, and the peak temperature of the endothermic DSC-transition was 55.9, 61.2 and 60.1 degreesC, respectively. The amylose content determined by gel permeation chromatography after debranching with isoamylase was 4% for A. xanthorriza, 18.4% for O. tuberosa. and 23.8% for C. edulis. The amylopectin showed different structures among the three starches with a beta-amylolysis limit of 67.6% for C edulis, 64.5% for O. tuberosa and 56.6% for A. xanthorriza. The average chain length of the amylopectin was highest for A. xanthorriza (22.6), followed by O. tuberosa with 22.4, and lowest for C. edulis (21.9). The complexation ability of the three starches was investigated by adding sodium dodecyl sulphate (SDS), and the amylose content was positively correlated with the enthalpy of the amylose-SDS complex. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 10. |
- Svegmark, K, et al.
(författare)
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Comparison of potato amylopectin starches and potato starches - influence of year and variety
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 47:4, s. 331-340
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Tidskriftsartikel (refereegranskat)abstract
- Starches from three potato varieties and their respective transformants producing amylopectin starch were studied over a period of 3 years. The gelatinisation, swelling and dispersion properties were studied using differential scanning calorimetry (DSC), X-ray diffraction, swelling capacity measurements and a Brabender Viscograph. The potato amylopectin starches (PAP) exhibited higher endothermic temperatures as well as higher enthalpies than the normal potato starches (NPS). PAP samples gave rise to an exceptionally sharp viscosity peak during gelatinisation and a relatively low increase in viscosity on cooling. Swelling capacity measurements showed that PAP granules swelled more rapidly, and that the dispersion of the swollen granules occurred at a lower temperature (85 degreesC). Analysis of variance (ANOVA) also revealed that the year influenced the DSC results, and that both year and variety affect some of the Brabender parameters. Furthermore, the PAP and NPS samples were subjected to heat-moisture treatment at three different moisture levels, and the Brabender viscosity properties were studied. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 11. |
- Wesslén, Bengt, et al.
(författare)
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Synthesis of amphiphilic amylose and starch derivatives
- 2002
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 47:4, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- For non-food uses starch generally is modified in order to obtain products with properties suitable for various applications. In the present work, starch and amylose were hydrophobically modified through reactions with long-chain alpha -alkyl epoxides (C-6 and C-12) in DMSO solution, in the presence of NaH as a catalyst. The molar substitution (MS) was calculated from NMR spectra. Derivatives with high as well as low MS values were obtained. In order to reach MS values above 1.5, the reaction had to be run for 150-300 h. Viscosity and GPC measurements indicated that the polysaccharides were degraded in DMSO under the influence of methyl sulfinyl anion, which presumably is the active catalyst. The derivatives were also characterized by FTIR. The ratio between the peak areas for OH stretching and alkyl stretching vibrations, respectively, in the FTIR spectra, was found to be proportional to MS values determined from NMR spectra. The solubility of the hydrophobically modified polysaccharide in various solvents was tested. Samples having C-12-alkyl side chains and MS > 1 were soluble in toluene. The C6 derivatives were water soluble up to a MS value of 0.3.
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| 12. |
- Anthonsen, M.W., et al.
(författare)
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Aggregates in acidic solutions of chitosans detected by static laser light scattering
- 1994
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 25:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- Chitosans having degrees of N-acetylation, FA, ranging from 0 to 0·6, were randomly degraded to different molecular weights and studied by multi angle static laser light scattering (LLS). Under the given experimental conditions, negative second virial coefficients of the solutions, A?2, revealed the presence of concentration dependent aggregates. Attempts to remove the aggregates, or to influence the aggregation behavior, were made by ultracentrifugation and extensive filtering of the solutions. Modification of the solvent conditions such as pH, ionic strength and temperature were carried out, and chitosan solutions were digested with an acidic proteinase. Non-degraded samples and chitosans prepared by both heterogeneous and homogeneous N-deacetylation of chitin were also studied. In all cases, the negative A?2 remained. However, it was observed that ultracentrifugation and filtering of the solutions decreased the measured molecular weights and radii of gyration, indicating that some of the material of high molecular weight and size could be removed by ultracentrifugation and filtration. The chemical nature of the physical basis of the molecular association was not revealed. Nevertheless, by the use of gel permeation chromatography coupled to an on-line low angle laser light scattering instrument and a differential refractive index concentration detector (HPSEC-LALLS-RI), a bimodal molecular weight distribution was observed in which about 5% of the sample had a very high molecular weight. These results coupled with the positive virial coefficients obtained earlier from osmotic pressure measurements suggest that a small fraction of the chitosan is aggregated to high molecular weight material, probably following a closed association model. Electron microscopy revealed the presence of some supramolecular structures. The positive second virial coefficients obtained earlier from osmometry are in harmony with these findings. The results demonstrate the occurrence of reversible aggregation in chitosan solutions. Static laser light scattering therefore cannot readily be used to determine molecular weights and sizes of chitosans under these conditions. It was not possible to correlate the extent of aggregation with the chemical composition of the chitosans. © 1994.
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| 13. |
- Berggren, R., et al.
(författare)
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Alkaline degradation of birch and spruce : influence of degradation conditions on molecular mass distributions and fibre strength
- 2003
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 51:3, s. 255-264
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Tidskriftsartikel (refereegranskat)abstract
- The alkaline degradation of birch and Norway spruce during kraft pulping was studied on a laboratory scale by two degradation strategies, by varying the pulping time using the same initial alkali level and by varying the initial alkali concentration using a constant time. The degradation at the molecular level was monitored by determining the carbohydrate composition, intrinsic viscosity and-molecular mass distribution (MMD). The influence of the degradation on fibre strength was studied as zero-span tensile index. The alkaline degradation was to a large extent homogeneous on a molecular level. However, some significant differences in degradation patterns were found. In the case of birch, the two different degradation strategies (increased alkali level and increased pulping time) caused differences in MMD and fibre strength (comparisons made at a given intrinsic viscosity or M-w). For spruce pulps, the decrease in fibre strength and the shift in MMD were the same in both series, regardless of degradation strategy.
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| 14. |
- Hermansson, Ann-Marie
(författare)
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Rheological and microstructural evidence for transient states during gelation of kappa-carrageenan in the presence of potassium
- 1989
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 10:3, s. 163-181
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Tidskriftsartikel (refereegranskat)abstract
- Kappa-carrageenan gelation was studied by a combination of electron microscopy and dynamic viscoelastic measurements. There was an initial maximum in the storage modulus during cooling and gel formation of 1% kappa-carrageenan in the presence of potassium. The structure of the transient state was found to consist of a fine network structure, where the junction zones were believed to be double helices. The structure had the characteristics of a true gel but was unstable. When the temperature was lowered aggregation took place and the fine network structure was partly broken down. Ordered superstrands formed which aligned themselves in parallel or were densely packed together. The degree of aggregation depended on the potassium ion concentration. In the weakest gel formed in 0·01 m KCl, the superstrands did not form a network but were rather dispersed in the fine network structure. In 0·1 and 0·2 m KCl the superstrands formed a three-dimensional network, where aligned superstrands formed the junction zones and branching occurred when superstrands deviated from each other and aligned with new superstrands. In 0·1 m KCl the supermolecular network dominated but in 0·2 m KCl a mixed gel was formed of the fine network and the coarse supermolecular network. The mixed gel gave rise to the firmest gel. © 1989.
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| 15. |
- Hermansson, Ann-Marie
(författare)
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Shear induced changes in the viscoelastic behaviour of heat treated potato starch dispersions
- 1990
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 13:1, s. 29-45
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Tidskriftsartikel (refereegranskat)abstract
- The viscoelastic behaviour of native potato starch dispersions was studied using dynamic viscoelastic measurements. The influence of various shear and heat treatments of gelatinized starch pastes were compared in the concentration range 4-10%. Heating had a minor effect compared to the effect of shear treatment. The complex modulus (G*) decreased to about 5% of its maximum value when the starch pastes were sheared during the heating cycle, whereas heating alone resulted in a decrease to about 60% of the maximum G* value. Shear also caused an increase in the phase angle and characteristic changes were observed with regard to frequency and strain dependencies. When samples were prepared in a Brabender viscograph, the shear induced changes took place early in the pasting cycle. The characteristics of the concentration dependence differed due to the shear history of the sample. Peculiar concentration dependencies, some even negative, could be obtained from samples with different shear histories. The results imply that even moderate shear treatment gives rise to structure changes which are reflected by a transition in the type of the viscoelastic behaviour. © 1990.
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| 16. |
- Lundin, Leif, et al.
(författare)
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Influence of locust bean gum on the rheological behaviour and microstructure of K-?-carrageenan
- 1995
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 28:2, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- Mixtures of ?-carrageenan-locust bean gum (LBG) were analysed by transmission electron microscopy and dynamic viscoelastic measurements. The effect of two different mannose:galactose (M:G) ratios of LBG on the rheology and microstructure of ?-carrageenan in KCl was studied. The rheological differences observed in the mixed gel as LBGs were added were found to be dependent on M:G ratio, salt concentration and LBG content. Monolayers of dilute samples of ?-carrageenan mixed with LBGs in varying ratios in 0.10 M KCl were visualised by low-angle rotary metal shadowing for transmission electron microscopy. The results obtained showed that LBG hindered the self-association of ?-carrageenan, and that the effect was enhanced at a higher M:G ratio and as the LBG contents were increased. Small deformation viscoelastic measurements were performed on ?-carrageenan-LBG mixtures in 0.050 and 0.10 M KCl at constant temperatures of 38 and 48 °C, respectively. Increased rheological stability was observed for mixtures containing a relatively high LBG content. Mixtures with a relatively low LBG content showed a maximum in storage modulus and an increase in phase angle. The stabilising effect of LBG on the rheology of the blends was more effective for the LBG with high M:G and as the LBG content was increased. © 1996.
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| 17. |
- Lundin, Leif, et al.
(författare)
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Supermolecular aspects of xanthan - locust bean gum gels based on rheology and electron microscopy
- 1995
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Ingår i: Carbohydrates polymer. - 0346-718X .- 0144-8617 .- 1879-1344. ; 26:2, s. 129-40
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Tidskriftsartikel (refereegranskat)abstract
- The viscoelastic properties and supermolecular structure of synergistic gels, formed by xanthan and locust bean gum (LBG) of two different mannose:galactose ratios (M:G), have been investigated by small deformation viscoelastic measurements and by low angle rotary-shadowing for transmission electron microscopy. The rheological properties at 20°C for mixtures subjected to heating and cooling cycles in the temperature range 30-80°C were found to be dependent on the M:G ratio. Mixtures of xanthan and LBG mixed at temperatures ?40°C were found to form true gels with low phase angles. Blends of xanthan and LBG with a low M:G ratio did not show any increase in synergistic effects as the temperature was increased, whilst the mixture of xanthan and LBG with a high M:G ratio showed a strong increase in synergistic effects as the temperature was raised above 60°C. A difference in gelation temperature (Tg) of approx.13°C was observed between the mixtures of xanthan and the two LBG fractions. The Tg for xanthan with a high M:G ratio was approx. 53°C, whilst the Tg for mixtures of xanthan and LBG with a low M:G ratio was approx. 40°C. Results obtained using electron microscopy showed that the xanthan-LBG network was formed from xanthan supermolecular strands, and addition of LBG did not influence the xanthan structure. The observed structural features of the gels were independent of heat treatment and LBG fraction. The structural similarities and rheological differences observed between xanthan and the LBG fractions are discussed in comparison with existing interaction models at the molecular level. Based on these results, a speculative network model at the supermolecular level is presented.
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| 18. |
- Stading, Mats, et al.
(författare)
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Humidity-induced structural transitions in amylose and amylopectin films
- 2001
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 45:3, s. 209-217
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Tidskriftsartikel (refereegranskat)abstract
- The effect of humidity on the dynamic mechanical and barrier properties and on the microstructure of amylose and amylopectin films was studied. The films were solution-gel-cast, with and without glycerol as added plasticizer, and dried to equilibrium weight under various relative humidities (RH). The network microstructure of glycerol-plasticized amylose films was shown to change from dense and homogeneous to a more open structure with fluctuations in the pore size when the surrounding RH was increased. The structural change was attributed to plasticization of the amorphous areas by increased water content, leading to higher mobility in the network and subsequent inhomogeneous swelling. This structural change had a direct influence on the oxygen permeability, which drastically increased. The onset of the increase occurred at lower surrounding RH for the films containing glycerol, and these films also had higher oxygen permeability. Glycerol-plasticized amylopectin films with gradually increased crystallinity were prepared by varying the RH during film formation. Dynamic mechanical analysis at both varied temperature and RH showed that the increased crystallinity led to higher glass transition temperature, T g, and a smaller effect of the surrounding humidity on mechanical and barrier properties. The RH during the formation of glycerol-plasticized amylose films did not affect crystallinity or T g. These films formed at 70% RH were shown to have a marked heterogeneous network. © 2001 Elsevier Science Ltd.
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| 19. |
- Stading, Mats, et al.
(författare)
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Rheological behaviour of mixed gels of kappa-carrageenan-locust bean gum
- 1993
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 22:1, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- Mixed gels of the K, Na and Ca-forms of ?-carrageenan and locust bean gum at a total polysaccharide concentration of 1% (w/w) were studied by dynamic viscoelastic measurements. Synergistic effects were only observed for mixed gels with K-?-carrageenan in ?0·1 m KCl. The composition favouring maximum synergy shifted from 90%-?-carrageenan in distilled water down to 35% K-?-carrageenan in 0·1 m KCl. Gels of K-?-carrageenan/locust bean gum did not show synergistic effects at high potassium concentration (0·2 m KCl). The typical behaviour of K-?-carrageenan at ?50 mm KCl dominated the rheological behaviour of the mixed systems even when the locust bean gum content was high. The synergistic effects probably originate from different mechanisms at low, 0-10 mm KCl, and high, 50-100 mm KCl, concentrations because of differences in the potassium-induced microstructure. The mixed gels with the Na or Ca-form of ?-carrageenan showed no synergy. Addition of locust bean gum caused the storage modulus to decrease and the phase angle to increase. The gels were weak, with G? < 170 Pa for the Na form and G? < 350 Pa for the Ca form. The mixed gels with both the Na and Ca forms had a broken frequency dependence of G?(f). © 1993.
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| 20. |
- Svegmark, Karin, et al.
(författare)
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Changes induced by shear and gel formation in the viscoelastic behaviour of potato, wheat and maize starch dispersions
- 1991
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 15:2, s. 151-169
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Tidskriftsartikel (refereegranskat)abstract
- The effect of shear and gel formation on the behaviour of heat-treated wheat, maize and potato starch dispersions was studied using dynamic viscoelastic measurements. The starch types were compared both at a concentration of 10% and at concentrations where the same level of shear forces was applied during the paste preparation procedure (11% wheat, 10% maize, and 4% potato). The cereal and the potato starch pastes initially showed similar viscoelastic properties after gelatinization, but the cereal starch pastes underwent a transition in their viscoelastic behaviour when cooled. This transition was believed to be due to the gelation of amylose. The main changes observed were a sharp increase in the shear modulus and a drop in the phase angle to below 2 degrees. No such transition occurred on cooling the potato starch pastes, at 25°C for 1 h, in the concentration range studied (4-10%).
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| 21. |
- Svegmark, K., et al.
(författare)
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Molecular structures obtained from mixed amylose and potato starch dispersions and their rheological behaviour
- 1993
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 22:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- Transmission electron microscopy (TEM) and dynamic viscoelastic measurements were used to study the effects of varying the ratio of potato starch to amylose. Solubilised amylose was mixed with two different types of potato starch: one with starch in the form of swollen granules and the other in the form of a molecular dispersion. The total concentration was kept constant at 8% (w/w). When the level of added amylose was low, the shear modulus (G*) was higher for gels with swollen granules than for molecular dispersions of starch. When the level of added amylose was high, the value of G* was approximately the same, independent of the type of starch structure. The rheological data were evaluated by a model treating the added amylose and potato starch as phase-separated systems. The model showed that the inherent amylose of potato starch did not contribute markedly to the gel strength caused by the added amylose. Potato starch alone does not form strong gels in the time scale studied. TEM studies confirmed that the inherent and the added amylose gave rise to completely different types of structure. The added amylose had an open network structure of stiff strands. This type of structure was found in the mixed systems with added amylose and starch, but not in systems with only potato starch. Solubilised amylopectin appeared to have a droplet-like structure, often found in the form of a string of beads. © 1993.
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| 22. |
- Abdelhamid, Hani Nasser, et al.
(författare)
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In-situ growth of zeolitic imidazolate frameworks into a cellulosic filter paper for the reduction of 4-nitrophenol
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 274
-
Tidskriftsartikel (refereegranskat)abstract
- Whatman (R) cellulosic filter paper was used as a substrate for the synthesis of two zeolitic imidazolate frameworks (ZIFs); ZIF-8 and ZIF-67 with and without 2,2,6,6-tetramethyl-1-piperidine oxoammonium salt (TEMPO) oxidized cellulose nanofibril (TOCNF). All synthesis procedures take place at room temperature via a one-pot procedure. The synthesis steps were followed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared (FT-IR). Data indicated the formation of metal oxide that converted to a pure phase of ZIFs after the addition of the organic linker i.e. 2-methyl imidazole (Hmim). The materials were characterized using XRD, FT-IR, SEM, energy dispersive X-ray (EDX), nitrogen adsorption-desorption isotherms, and X-ray photoelectron microscope (XPS). Data analysis confirms the synthesis of ZIFs into Whatman (R) filter paper. The materials were used for the reduction of pollutants such as 4-nitrophenol (4-NP) compound to 4-aminophenol (4-AP). The materials exhibit high potential for water treatment and may open new exploration for hybrid materials consisting of cellulose and ZIFs.
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| 23. |
- Abdul Hadi, N., et al.
(författare)
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Characterization and stability of short-chain fatty acids modified starch Pickering emulsions
- 2020
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- Acetylated, propionylated and butyrylated rice and quinoa starches at different levels of modification and starch concentrations, were used to stabilize oil-in-water starch Pickering emulsions at 10% oil fraction. Short-chain fatty acid modified starch Pickering emulsions (SPEs) were characterized after emulsification and after 50 days of storage. The particle size distribution, microstructure, emulsion index, and stability were evaluated. An increase in starch concentration led to a decrease of emulsion droplet sizes. Quinoa starch has shown the capability of stabilizing Pickering emulsions in both the native and modified forms. The emulsifying capacity of SPEs was improved by increasing the chain length of SCFA. Modified quinoa starch with higher chain lengths (i.e. propionylated and butyrylated), at higher levels of modification, showed higher emulsion index (>71%) and stability over the entire 50 days storage. At optimized formulation, SCFA-starch particles have the potential in stabilizing emulsions for functional foods, pharmaceutical formulations, or industrial food applications.
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| 24. |
- Abid, Suleman, et al.
(författare)
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Synthesis and characterization of glycol chitosan coated selenium nanoparticles acts synergistically to alleviate oxidative stress and increase ginsenoside content in Panax ginseng
- 2021
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 267
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of the present study is synthesis of glycol chitosan coated selenium nanoparticles (GC-Se NPs) and evaluation of oxidative stress and ginsenoside accumulation in P. ginseng C. A. Meyer. We synthesized (Se NPs and GC-Se NPs) and characterized using various spectroscopic analyses. The highest concentration (20 mg L−1) of GC-Se NPs induced moderate ROS (O2[rad]− and H2O2) accumulation and upregulation of PgSOD and PgCAT showing good biocompatibility and less toxicity at the highest concentration. Furthermore, ginsenoside biosynthetic pathway genes (PgHMGR, PgSS, PgSE, PgDDS) also showed significant upregulation upon 20 mg L−1 GC-Se NPs treatment. At 20 mg L−1 GC-Se NPs treatment, ginsenoside accumulated upto 217.47 mg/mL and 169.86 mg/mL mainly due to the increased proportion of Rb1 and Re ginsenosides. Altogether, our results suggested that ecofriendly conjugation of GC with Se NPs could be used as a bio fortifier to enhance the ginsenoside profile and to increase the quality of ginseng roots.
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| 25. |
- Abitbol, Tiffany, et al.
(författare)
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Cellulose nanocrystal/low methoxyl pectin gels produced by internal ionotropic gelation.
- 2021
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 260
-
Tidskriftsartikel (refereegranskat)abstract
- The biotechnological applications of cellulose nanocrystals (CNCs) continue to grow due to their sustainable nature, impressive mechanical, rheological, and emulsifying properties, upscaled production capacity, and compatibility with other materials, such as protein and polysaccharides. In this study, hydrogels from CNCs and pectin, a plant cell wall polysaccharide broadly used in food and pharma, were produced by calcium ion-mediated internal ionotropic gelation (IG). In the absence of pectin, a minimum of 4 wt% CNC was needed to produce self-supporting gels by internal IG, whereas the addition of pectin at 0.5 wt% enabled hydrogel formation at CNC contents as low as 0.5 wt%. Experimental data indicate that CNCs and pectin interact to give robust and self-supporting hydrogels at solid contents below 2.5 %. Potential applications of these gels could be as carriers for controlled release, scaffolds for cell growth, or wherever else distinct and porous network morphologies are required.
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| 26. |
- Albornoz-Palma, Gregory, et al.
(författare)
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Relationship between rheological and morphological characteristics of cellulose nanofibrils in dilute dispersions
- 2019
-
Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344.
-
Tidskriftsartikel (refereegranskat)abstract
- The morphology of cellulose nanofibrils (CNFs), the rheological characteristics of their dispersions, and the corresponding relationships, are fundamental for understanding the properties of the material. This work aims at understanding how the morphological characteristics of the CNFs affect the rheology of the dispersions in the dilute region and to establish a relationship between both properties. A strong relationship was observed between the intrinsic viscosity of the CNF dispersions and their aspect ratio, which can be correlated through the expression ρ[η]=0.051p1.85. When comparing the model obtained in this work to the wormlike chain model, it was possible to verify that these models are independent of the flexibility of the CNFs. Regarding the fibrillation process, the dynamic viscosity only reflects part of the behavior of the morphological properties of the CNFs and does not provide reliable data that would allow these characteristics to be inferred, while the intrinsic viscosity does allow this relationship.
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| 27. |
- Altskär, Annika, et al.
(författare)
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Some effects of processing on the molecular structure and morphology of thermoplastic starch
- 2008
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 71:4, s. 591-597
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of high-molecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials. © 2007 Elsevier Ltd. All rights reserved.
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| 28. |
- Alves, Luis, et al.
(författare)
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Dissolution state of cellulose in aqueous systems. 2. Acidic solvents
- 2016
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 151, s. 707-715
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution.
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| 29. |
- Alves, Luis, et al.
(författare)
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Revisiting the dissolution of cellulose in H3PO4(aq) through cryo-TEM, PTssNMR and DWS
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 252
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose can be dissolved in concentrated acidic aqueous solvents forming extremely viscous solutions, and, in some cases, liquid crystalline phases. In this work, the concentrated phosphoric acid aqueous solvent is revisited implementing a set of advanced techniques, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR), and diffusing wave spectroscopy (DWS). Cryo-TEM images confirm that this solvent system is capable to efficiently dissolve cellulose. No cellulose particles, fibrils, or aggregates are visible. Conversely, PTssNMR revealed a dominant CP signal at 25 °C, characteristic of C-H bond reorientation with correlation time longer than 100 ns and/or order parameter above 0.5, which was ascribed to a transient gel-like network or an anisotropic liquid crystalline phase. Increasing the temperature leads to a gradual transition from CP to INEPT-dominant signal and a loss of birefringence in optical microscopy, suggesting an anisotropic-to-isotropic phase transition. Finally, an excellent agreement between optical microrheology and conventional mechanical rheometry was also obtained.
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| 30. |
- Amaral, Sarah da Costa, et al.
(författare)
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Cytotoxic effect of crude and purified pectins from Campomanesia xanthocarpa Berg on human glioblastoma cells
- 2019
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Ingår i: Carbohydrate Polymers. - : ELSEVIER SCI LTD. - 0144-8617 .- 1879-1344. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- A new source of pectin with a cytotoxic effect on glioblastoma cells is presented. A homogeneous GWP-FP-S fraction (M-w, of 29,170 g mol(-1)) was obtained by fractionating the crude pectin extract (GW) from Campomanesia xanthocarpa pulp. According to the monosaccharide composition, the GWP-FP-S was composed of galacturonic acid (58.8%), arabinose (28.5%), galactose (11.3%) and rhamnose (1.1%), comprising 57.7% of homogalacturonans (HG) and 42.0% of type I rhamnogalacturonans (RG-I). These structures were characterized by chromatographic and spectroscopic methods; GW and GWP-FP-S fractions were evaluated by MIT and crystal violet assays for their cytotoxic effects. Both fractions induced cytotoxicity (15.55-37.65%) with concomitant increase in the cellular ROS levels in human glioblastoma cells at 25-400 mu g mL(-)(1), after 48 h of treatment, whereas no cytotoxicity was observed for normal NIH 3T3 cells. This is the first report of in vitro bioactivity and the first investigation of the antitumor potential of gabiroba pectins.
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| 31. |
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| 32. |
- Andersson, Mariette, et al.
(författare)
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A simplified method of determining the internal structure of amylopectin from barley starch without amylopectin isolation
- 2021
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 255
-
Tidskriftsartikel (refereegranskat)abstract
- To determine the internal structure of barley starch without amylopectin isolation, whole starch was hydrolyzed using beta-amylase to remove the linear amylose and obtain beta-limit dextrins (beta-LDs). The beta-LDs were treated with extensive a-amylase to prepare alpha-limit dextrins (alpha-LDs), and the alpha-LDs were further hydrolyzed with beta-amylase into building blocks. The chain-length distribution of beta-LD and building block composition were analyzed by sizeexclusion chromatography and anion-exchange chromatography. The internal structure of the barley whole starches had similar pattern to barley amylopectins analyzed by conventional methods. The starch of barley amol-mutated varieties contained more short internal B-chains and less long internal B-chains than that of other varieties. The starch from amol-mutated varieties had more large building blocks than that from waxy varieties. The simplified method presented in this study can effectively characterize starch internal structure that relates to physicochemical properties of starch, although some details of amylopectin structure are not assessable.
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| 33. |
- Andersson, Roger
(författare)
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Inter-laboratory evaluation of SEC-post-column calcofluor for determination of the weight-average molar mass of cereal β-glucan
- 2015
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 124, s. 254-264
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Tidskriftsartikel (refereegranskat)abstract
- Even though size exclusion chromatography (SEC) with post column addition of calcofluor (SEC-calcofluor) has been used for the determination of cereal beta-glucan molar mass in foods for many years, there is a lack of systematic evaluation of the method. To address this issue a set of suitable beta-glucan standards were generated by preparative SEC and their molar mass characteristics were determined by analytical multi-detection SEC (refractive index (RI), light scattering). Each standard was then analysed by SEC-calcofluor at three different labs. As a direct comparison, the analyses were repeated with a RI detector. For SEC-calcofluor accurate measurements of weight average molar mass (M-w) can be made for beta-glucan populations within 10-500 x 10(3) g/mol. Above this molar mass threshold there is an increasing tendency for underestimation of M-w. Precipitation of some beta-glucan-calcofluor complexes may have delayed their transport into the detector. (C) 2015 Elsevier Ltd. All rights reserved.
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| 34. |
- Andersson, Roger
(författare)
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Soluble beta-1,3/1,6-glucan in seaweed from the southern hemisphere and its immunomodulatory effect
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 92, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- Five types of macroalgae from the southern hemisphere were analysed for the presence of beta-1,3/1,6-glucan and its immunostimulant properties. We were able to extract soluble beta-1,3/1,6-D-glucan from Durvillaea antarctica (Chamisso) Harlot (DA). The morphology of the brown algae influenced extraction, and the highest percentage of beta-glucan was found in the fronds. The content of beta-glucan in the stipes and holdfast was on average 33% and <5%, respectively, of that in the fronds. A simple laboratory extraction process was developed. A highly pure water-soluble polysaccharide, mainly composed of glucose residues, was obtained with a dominant average molecular weight of 6.9 kDa. NMR spectroscopy confirmed the polysaccharide structure to be of beta-1,3/1,6-glucan type, comprising a beta-1,3-glucan backbone and 21% degree of branching of beta-1,6-glucan side chains. Mouse cells were exposed to four DA extract concentrations in water (50, 100, 250 and 500 mu g/mL) and no adverse effects on survival were noted. Remarkably, the beta-glucan induced a 16.9% increase in activated CD19+ B lymphocytes compared with the control sample. The optimal concentration for maximum activity was 100 mu g DA extract/mL. (C) 2012 Elsevier Ltd. All rights reserved.
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| 35. |
- Andrade Pires, Amanda do Rocio, et al.
(författare)
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Cytotoxic effect of a mannogalactoglucan extracted from Agaricus bisporus on HepG2 cells
- 2017
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Ingår i: Carbohydrate Polymers. - : ELSEVIER SCI LTD. - 0144-8617 .- 1879-1344. ; 170, s. 33-42
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Tidskriftsartikel (refereegranskat)abstract
- A mannogalactoglucan (RK2-Ab; M-w, 1.8 x 10(4) g mol(-1)) composed by Man (27.3%), Gal (24.4%) and Glc (48.3%) was extracted and characterized from Agaricus bisporus, and its biological activity was evaluated on human hepatocarcinoma cells (HepG2). The partially-O-methylated alditol acetates together with the NMR data suggest the main chain to be composed of alpha-D-Galp (32.8%) and beta-D-Glcp (37.0%) units (1 -> 6) -linked, with beta-D-Manp (14.6%), as non-reducing end units, substituting the side chains at O-2 (alpha-D-Galp units; 3.3%) and O-2 and O-4 (beta-D-Glcp units; 3.6%). (1 -> 2) -linked beta-D-Glcp (2.7%) and beta-D-Manp (6.0%) can also be observed. RK2-Ab reduced cellular viability of HepG2 cells, by both, the MTT and lactate dehydrogenase release assays, promoted the increase of cytochrome c release and decrease of ATP content. Suggesting that the mannogalactoglucan from A. bisporus may have antitumor activity by inducing apoptosis by the mitochondria death pathway, and could be used in cancer therapy.
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| 36. |
- Anugwom, I, et al.
(författare)
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Selective Extraction of Hemicelluloses from Spruce using Switchable Ionic Liquids
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 87:3, s. 2005-2011
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Tidskriftsartikel (refereegranskat)abstract
- Switchable Ionic Liquids (SILs) made from alcohols, either hexanol or butanol, and CO2 together with an amidine (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)) were investigated as dissolution/fractionation solvents for wood material. Both native spruce (Picea abies), and pre-extracted spruce were treated with either butanol SIL (SIL1) or hexanol SIL (SIL 2) for 5 days at 55 °C under normal pressure. The SILs were formed by bubbling CO2 through an equimolar mixture of either 1-hexanol or 1-butanol and DBU. The viscosity of the mixture increased from 7.1 mPas to 2980 mPas for SIL 2 and 5.1 to 1600 mPas for SIL 1. Melting points of the SILs 1 and 2 were at 8 and 14 °C, respectively. After the treatment time (5 days), the undissolved fraction contained 38 wt % less hemicelluloses compared to native spruce. There was an increase in the glucose content of the milled spruce treated with both SILs, since the milling step reduced the cellulose crystallinity of the wood and facilitated an easier SIL access into the wood. The solvents were very neutral in terms of lignin removal. Consequently, only about 2% of the lignin was removed from native wood. Moreover, a priori removal of the wood extractives did not influence the lignin removal. Highlights► Switchable Ionic Liquids made from, either hexanol or butanol, and CO2 together with an amidine (DBU) were studies as dissolution/fractionation solvents for spruce wood. ► After the treatment undissolved fraction contained 38 wt-% less hemicelluloses. ► We conclude that Switchable ionic liquids are effective solvent for fractionation of wood material, and they are easily recycled and can be reused.
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| 37. |
- Asaadi, Shirin, et al.
(författare)
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Structural analysis of Ioncell-F fibres from birch wood
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 181, s. 893-901
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Tidskriftsartikel (refereegranskat)abstract
- Quite recently, the Ioncell-F process, a novel and promising Lyocell fibre process, has been developed. The ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH]OAc) utilized in this process, was identified as an excellent cellulose solvent for dry-jet wet fibre spinning. Fibres spun from cellulose-[DBNH]OAc solution have shown excellent mechanical properties. Herein, various structural features of these ionic liquid-based fibres were analyzed and correlated with their mechanical properties. The highest slope of tenacity increase of these Ioncell-F fibres (from birch wood) observed at low draw ratios (DRs), while a continuous but slower increase occurs to partly very high draws. The improvements in the mechanical properties do not seem to correlate with changes in the crystallite size or the crystalline orientation based on wide-angle X-ray scattering (WAXS) results. More significant differences were seen for the sample crystallinity, the amorphous orientation (measured by birefringence), the orientation of the voids, the specific surface (measured by small-angle X-ray scattering (SAXS)), and the sorption/desorption properties of the fibres.
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| 38. |
- Atoufi, Zhaleh, et al.
(författare)
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Surface tailoring of cellulose aerogel-like structures with ultrathin coatings using molecular layer-by-layer assembly
- 2022
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 282
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibril-based aerogels have promising applicability in various fields; however, developing an effi-cient technique to functionalize and tune their surface properties is challenging. In this study, physically and covalently crosslinked cellulose nanofibril-based aerogel-like structures were prepared and modified by a mo-lecular layer-by-layer (m-LBL) deposition method. Following three m-LBL depositions, an ultrathin polyamide layer was formed throughout the aerogel and its structure and chemical composition was studied in detail. Analysis of model cellulose surfaces showed that the thickness of the deposited layer after three m-LBLs was approximately 1 nm. Although the deposited layer was extremely thin, it led to a 2.6-fold increase in the wet specific modulus, improved the acid-base resistance, and changed the aerogels from hydrophilic to hydrophobic making them suitable materials for oil absorption with the absorption capacity of 16-36 g/g. Thus, demon-strating m-LBL assembly is a powerful technique for tailoring surface properties and functionality of cellulose substrates.
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| 39. |
- Azhar, Shoaib, 1980-, et al.
(författare)
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Extraction of hemicelluloses from fiberized spruce wood
- 2015
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 117, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses.
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| 40. |
- Bai, Yunfei, et al.
(författare)
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Sustainable cellulose foams for all-weather high-performance radiative cooling and building insulation
- 2024
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 333, s. 121951-
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Tidskriftsartikel (refereegranskat)abstract
- Passive daytime radiative cooling (PDRC) as a zero-energy-consumption cooling technique offers rich opportunities in reducing global energy consumption and mitigating CO2 emissions. Developing high-performance PDRC coolers with practical applicability based on sustainable materials is of great significance, but remains a big challenge. Herein, polyvinyl alcohol (PVA) and esterified cellulose (EC) extracted from sawdust were used as raw materials to construct foams by using a dual-crosslinking assisted-unidirectional freeze-drying strategy followed by hydrophobic surface modification. The resultant PVA/EC (PEC) foams with ideal hierarchical macropore structure displayed various excellent features, such as low thermal conductivity (26.2 mW·m−1·K−1), high solar reflectance (95 %) and infrared emissivity (0.97), superhydrophobicity as well as high mechanical properties. The features allowed the PEC foams to be used as radiative coolers with excellent PDRC performance and thermal insulating materials. A maximum sub-ambient temperature drops of 10.2 °C could be achieved for optimal PEC foams. Building simulations indicated that PEC foams could save 55.8 % of the energy consumption for Xi'an. Our work would give inspiration for designing various types of PDRC coolers, including but certainly not limited to foams-based radiative coolers.
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| 41. |
- Balusamy, Sri Renukadevi, et al.
(författare)
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Chitosan, chitosan nanoparticles and modified chitosan biomaterials, a potential tool to combat salinity stress in plants
- 2022
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 284
-
Forskningsöversikt (refereegranskat)abstract
- Chitosan being non-toxic, biocompatible, and biodegradable gained considerable interest among agriculturists. Our research review discusses about the role of Cs, chitosan nanoparticles (CsNPs), and modified chitosan biomaterials (CsBMs) under salt stress to improve growth parameters such as plant height, weight, stem width, fruit yield, pigments such as chlorophyll a, b, total chlorophyll, and carotenoid contents, as well as antioxidant and non-antioxidative enzymes. Upon Cs treatment and salt stress, total aminoacids (TAA), glutamic acids, and gamma-aminobutyric acid (GABA) were increased. Furthermore, Cs activated SOS1 pathway and increased various gene transcripts involved in sodium compartmentalization, proton motive force, energy production, and phenol metabolism. On the other hand, CsNPs and modified CsBMs treated plants under salinity stress increased indole terpene alkaloid metabolism, defense related genes, decreased ROS production by enhancing JA signaling, increased essential oil, anthocyanins, membrane stability, alkaloids, and diterpene glycosides. This is the first review that specifically brings insights about the physiological and biochemical parameters of the plants by comparing Cs/CsNPs/modified CsBMs treatment options under salt stress and encourages the use of CsNPs and modified CsBMs compared to Cs for better plant function under salinity stress.
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| 42. |
- Bannak Gedara, Shishanthi Jayarathna, et al.
(författare)
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High fructan barley lines produced by selective breeding may alter beta-glucan and amylopectin molecular structure
- 2023
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 316
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Tidskriftsartikel (refereegranskat)abstract
- Six cross-bred barley lines developed by a breeding strategy with the target to enhance the fructan synthesis activity and reduce the fructan hydrolysis activity were analyzed together with their parental lines, and a reference line (Gustav) to determine whether the breeding strategy also affected the content and molecular structure of amylopectin and beta-glucan. The highest fructan and beta-glucan content achieved in the novel barley lines was 8.6 % and 12 %, respectively (12.3-fold and 3.2-fold higher than in Gustav). The lines with low fructan synthesis activity had higher starch content, smaller building blocks in amylopectin, and smaller structural units of beta-glucans than the lines with high-fructan synthesis activity. Correlation analysis confirmed that low starch content was associated with high amylose, fructan, and beta-glucan content, and larger building blocks in amylopectin.
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| 43. |
- Barbieri, Shayla Fernanda, et al.
(författare)
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Extraction, purification and structural characterization of a galactoglucomannan from the gabiroba fruit (Campomanesia xanthocarpa Berg), Myrtaceae family
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 174, s. 887-895
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we isolated and structurally characterized, for the first time, a galactoglucomannan (GGM) from the pulp of gabiroba, a Myrtaceae family species. The HPSEC-MALLS-RI analysis showed a homogeneous polysaccharide with molar mass of 25,340 g mol(-1). The monosaccharide composition showed that the GGM consisted of Man:Glc:Gal in a molar ratio of 1:1:0.6. Methylation and 1D and 2D NMR analyses suggested that the main chain of the GGM consisted of beta-D-Glcp and beta-D-Manp units (1 -> 4)-linked. The alpha-D-Galp substitutions occur mainly at O-6 position of beta-D-Manp units. The glycosidic linkages of the GGM were evident by the presence of the characteristic signals of 4-O-substituted residues at delta 78.6/3.69 for both beta-D-Glcp and beta-D-Manp. Furthermore, the 0-6 substitutions for both beta-D-Glcp and beta-D-Manp units were confirmed by signals at delta 67.1/4.00 and 3.93. The interglycosidic correlations, obtained through the analysis of the HMBC spectrum, further confirm the structure. (C) 2017 Elsevier Ltd. All rights reserved.
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| 44. |
- Barbieri, Shayla Fernanda, et al.
(författare)
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Pectins from the pulp of gabiroba (Campomanesia xanthocarpa Berg) : Structural characterization and rheological behavior
- 2019
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 214, s. 250-258
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Tidskriftsartikel (refereegranskat)abstract
- The pulp of gabiroba fruits was submitted to a hot water extraction, giving rise to a crude pectin named GW. GW was shown to be composed mainly of arabinose (54.5%), galacturonic acid (33.5%), galactose (7.6%), and rhamnose (1.6%). GW was characterized by chromatographic and spectroscopic methods indicating the presence of homogalacturonans (HG) with a degree of methyl-esterification (DM) of 60% and rhamnogalacturonans I (RG-I). HG domain represents 31.9% and RG-I domain 65.3%. Furthermore, GW was submitted to sequential fractionation methods, giving rise to GWP-TEP fraction, structurally characterized by the predominance of HG regions, and confirmed by NMR analysis. The rheological behavior of GW was analyzed at 1%, 3%, and 5% (w/v) concentration with 0.1 mol L-1 NaCl. All samples showed shear thinning behavior. In the oscillatory measurements, the 1% GW showed a liquid-like behavior, while the 3% presented a concentrated solution behavior and the 5% GW a gel behavior.
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| 45. |
- Basu, Alex, et al.
(författare)
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Ion-crosslinked wood-derived nanocellulose hydrogels with tunable antibacterial properties : Candidate materials for advanced wound care applications
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 181, s. 345-350
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Tidskriftsartikel (refereegranskat)abstract
- Development of advanced dressings with antimicrobial properties for the treatment of infected wounds is an important approach in the fight against evolution of antibiotic resistant bacterial strains. Herein, the effects of ion-crosslinked nanocellulose hydrogels on bacteria commonly found in infected wounds were investigated in vitro. By using divalent calcium or copper ions as crosslinking agents, different antibacterial properties against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa were obtained. Calcium crosslinked hydrogels were found to retard S. epidermidis growth (up to 266% increase in lag time, 36% increase in doubling time) and inhibited P. aeruginosa biofilm formation, while copper crosslinked hydrogels prevented S. epidermidis growth and were bacteriostatic towards P. aeruginosa (49% increase in lag time, 78% increase in doubling time). The wound dressing candidates furthermore displayed barrier properties towards both S. epidermidis and P. aeruginosa, hence making them interesting for further development of advanced wound dressings with tunable antibacterial properties.
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| 46. |
- Basu, Alex, et al.
(författare)
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On the use of ion-crosslinked nanocellulose hydrogels for wound healing solutions : Physicochemical properties and application-oriented biocompatibility studies
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 174, s. 299-308
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Tidskriftsartikel (refereegranskat)abstract
- Calcium ion-crosslinked nanofibrillated cellulose (NFC) hydrogels were investigated as potential materials for wound healing dressings. The physicochemical properties of the hydrogels were examined by rheology and water retention tests. Skin cells and monocytes were selected for application-oriented bio-compatibility studies. The NFC hydrogels presented entangled fibrous networks and solid-like behavior. Water retention tests showed the material's potential to maintain a suitable moist environment for different type of wounds. The hydrogels did not affect dermal fibroblasts monolayer cultures upon directcontact, as cell monolayers remained intact after application, incubation and removal of the materials. Inflammatory response studies with blood-derived mononuclear cells revealed the inert nature of the hydrogels in terms of cytokine secretion and reactive oxygen species production. Results highlight the great potential of ion-crosslinked NFC hydrogels for the development of advanced wound dressings, where further functionalization of the material could lead to improved properties towards the healing of specific wound types.
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| 47. |
- Behroozi Kohlan, Taha, et al.
(författare)
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Schiff base crosslinked hyaluronic acid hydrogels with tunable and cell instructive time-dependent mechanical properties
- 2024
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic interplay between cells and their native extracellular matrix (ECM) influences cellular behavior, imposing a challenge in biomaterial design. Dynamic covalent hydrogels are viscoelastic and show self-healing ability, making them a potential scaffold for recapitulating native ECM properties. We aimed to implement kinetically and thermodynamically distinct crosslinkers to prepare self-healing dynamic hydrogels to explore the arising properties and their effects on cellular behavior. To do so, aldehyde-substituted hyaluronic acid (HA) was synthesized to generate imine, hydrazone, and oxime crosslinked dynamic covalent hydrogels. Differences in equilibrium constants of these bonds yielded distinct properties including stiffness, stress relaxation, and self-healing ability. The effects of degree of substitution (DS), polymer concentration, crosslinker to aldehyde ratio, and crosslinker functionality on hydrogel properties were evaluated. The self-healing ability of hydrogels was investigated on samples of the same and different crosslinkers and DS to obtain hydrogels with gradient properties. Subsequently, human dermal fibroblasts were cultured in 2D and 3D to assess the cellular response considering the dynamic properties of the hydrogels. Moreover, assessing cell spreading and morphology on hydrogels having similar modulus but different stress relaxation rates showed the effects of matrix viscoelasticity with higher cell spreading in slower relaxing hydrogels.
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| 48. |
- Benediktsdottir, Berglind E., et al.
(författare)
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Synthesis of N,N,N-trimethyl chitosan homopolymer and highly substituted N-alkyl-N,N-dimethyl chitosan derivatives with the aid of di-tert-butyldimethylsilyl chitosan
- 2011
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 86:4, s. 1451-1460
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Tidskriftsartikel (refereegranskat)abstract
- A highly chemoselective strategy for the synthesis of N,N,N-trimethyl chitosan (TMC) homopolymer and highly substituted N-alkyl-N,N-dimethyl chitosan derivatives was achieved using di-tert-butyldimethylsilyl-3,6-O-chitosan (di-TBDMS chitosan) as a precursor. The influence of different solvents, reagents and other reaction conditions on the reduction, trimethylation and quaternization of these di-TBDMS chitosan derivatives was studied. Products were characterized by NMR after each step. Di-TBDMS chitosan was reacted with methyl iodide in NMP, giving a 100% substituted TMC with the trimethyl group appearing at 3.35 ppm in H-1 NMR spectrum. N-Propyl-, N-butyl- and N-hexyl-N,N-dimethyl chitosan derivatives were synthesized by stepwise reductive alkylation of di-TBDMS chitosan, followed by quaternization with dimethyl sulfate in dichloromethane, giving 65-72% substituted N-alkyl-N,N-dimethyl chitosan derivatives under optimized conditions. Analysis of these water-soluble chitosan derivatives by FT-IR, H-1 NMR, C-13 NMR, H-1-H-1 COSY and H-1-C-13 HSQC NMR enabled detailed structural characterization. All peaks could be assigned to N-modification, showing the selectivity of the di-TBDMS protection. (C) 2011 Elsevier Ltd. All rights reserved.
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| 49. |
- Bergström, Elina Mabasa, et al.
(författare)
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Plasticized xyloglucan for improved toughness-Thermal and mechanical behaviour
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 87:4, s. 2532-2537
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Tidskriftsartikel (refereegranskat)abstract
- Tamarind seed xyloglucan is an interesting polysaccharide of high molar mass with excellent thermomechanical properties. Several plasticizers were studied in order to facilitate thermal processing and improve toughness (work to fracture) of xyloglucan film materials: sorbitol, urea, glycerol and polyethylene oxide. Films of different compositions were cast and studied by thermogravimetric analysis (TGA), calorimetry (DSC), dynamic mechanical thermal analysis (DMA) and tensile tests. Results are analysed and discussed based on mechanisms and practical considerations. Highly favourable characteristics were found with XG/sorbitol combinations, and the thermomechanical properties motivate further work on this material system, for instance as a matrix in biocomposite materials.
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| 50. |
- Berillo, Dmitriy, et al.
(författare)
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3D-macroporous chitosan-based scaffolds with in situ formed Pd and Pt nanoparticles for nitrophenol reduction
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 192, s. 166-175
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Tidskriftsartikel (refereegranskat)abstract
- 3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20–0.53 h−1. The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30–40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol.
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