| 11. |
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| 12. |
- Lambo, Adele, et al.
(författare)
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Molar mass and rheological characterisation of an exopolysaccharide from Pediococcus damnosus 2.6
- 2007
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 68:3, s. 577-586
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Tidskriftsartikel (refereegranskat)abstract
- The molar mass and theological properties of an exopolysaccharide (EPS) from Pediococcus damnosus 2.6 were investigated. The molar mass was determined by asymmetrical flow field-flow fractionation coupled with multiangle light scattering and refractive index detection. The EPS was observed to be a flexible chain polymer with a molar mass value of 4 x 10(6) g mol(-1). Heating the sample at 80 degrees C for 10 min caused a shift to lower hydrodynamic radius. The theological behaviour of the EPS was compared to that of a commercial cereal beta-glucan (0.359 x 10(6) g mol(-1)). The maximum storage modulus, G'(max) for EPS solution was lower than that for the cereal beta-glucan at all concentrations, while the relaxation time, t(G'=G") was higher. The G'(max) was reduced on heating the EPS solution at 80 degrees C for 10 min, likely indicating some conformational changes. Three-dimensional models of the polymers revealed some differences in intramolecular hydrogen bonds. The EPS molecule had a ropy nature in solution and this could make it suitable for usage as a thickener in food systems. (c) 2006 Elsevier Ltd. All rights reserved.
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| 13. |
- Leeman, Margareta, et al.
(författare)
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Resistant starch formation in temperature treated potato starches varying in amylose/amylopectin ratio
- 2006
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 65:3, s. 306-313
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Tidskriftsartikel (refereegranskat)abstract
- Two genetically modified potato starches derived from the same mother line (64%, 1% and 23% amylose, respectively) were used to study the bioavailability after various heat treatments. The conditions for the treatments were of minor importance for resistant starch (RS) formation and hydrolysis results, as compared to the proportion of amylose. A high amylose content gave lower hydrolysis index (HI) and higher amounts of RS than starches with less amylose. Retrograded amylopectin contributed to a decreased HI, although only the high amylose line showed sufficient reduction in predicted glycaemic indices (Gl). The line with high amylose content contained 25-30% RS vs. in the range of 0-5% for the other starches. Results could neither be explained by the presence of intact granules, nor by the content of retrograded amylose. Therefore, a synergistic effect between the starch components was suggested to affect the RS and starch hydrolysis. (c) 2006 Elsevier Ltd. All rights reserved.
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| 14. |
- Lôpez-Rubio, A., et al.
(författare)
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Enhanced film forming and film properties of amylopectin using micro-fibrillated cellulose
- 2007
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 68:4, s. 718-727
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a novel approach to produce amylopectin films with enhanced properties by the addition of micro fibrillated cellulose (MFC). Aqueous dispersions of gelatinized amylopectin, glycerol (0-38 wt%) and MFC (0-10 wt%) were cast at ambient temperature and 50% relative humidity and, after 10 days of storage, the tensile properties were investigated. The structure of the composite films was revealed by optical, atomic force and transmission electron microscopy. The moisture content was determined by thermogravimetry and the temperature-dependent film rigidity was measured by thermal mechanical analysis. Synchrotron simultaneous small- and wide-angle X-ray measurements revealed that the solutions had to be heated to above 85 degrees C in order to achieve complete gelatinization. Optical microscopy and atomic force microscopy revealed uniformly distributed MFC aggregates in the films, with a length of 10-90 mu m and a width spanning from a few hundred nanometers to several microns. Transmission electron microscopy showed that, in addition to aggregates, single MFC microfibrils were also embedded in the amylopectin matrix. It was impossible to cast antylopectin films of sufficient quality with less than 38 wt% glycerol. However, when MFC was added it was possible to produce high quality films even without glycerol. The film without glycerol was stiff and strong but not brittle. It was suggested that this remarkable effect was due to its comparatively high moisture content. Consequently MFC acted both as a "conventional" reinforcement because of its fibrous structure and also indirectly as a plasticiser because its presence led to an increase in film moisture content.
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| 15. |
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| 16. |
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| 17. |
- Mira, Isabel, et al.
(författare)
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On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. : Part II: A confocal laser scanning microscopy study
- 2007
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 68:4, s. 637-646
-
Tidskriftsartikel (refereegranskat)abstract
- The location and penetration patterns of two fluorescently labelled, surface active molecules into normal and waxy wheat starch granules prior, during and after the temperature-induced gelatinization were studied by means of confocal laser scanning microscopy (CLSM). Amphiphilic dyes were found to have a tendency to penetrate wheat starch granules in aqueous suspension. The penetration patterns were however found to be dependent on the contact time, type of starch and the chain length (C-12 vs. C-16) of the amphiphilic dye. The penetration of amphiphilic dyes through the starch granule matrix proved to be less restricted in waxy than in normal wheat starch. For a given type of starch, the penetration of the longer chain dye was more constrained than that of the shorter chain one. The extent to which the dye diffuses into the granule matrix as it gelatinizes is also affected by the chain length of the dye, diffusion of the shorter chain dye occurring more profusely and at lower temperatures than for the longer chain one. These differences are suggested to be related to the dissociation temperature of the ANI-amphiphilic dye complexes.
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| 18. |
- Mira, Isabel, et al.
(författare)
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On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. : Part I. Pasting and calorimetric studies
- 2007
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 68:4, s. 665-678
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Tidskriftsartikel (refereegranskat)abstract
- Pasting and calorimetric studies of normal and waxy wheat starch were performed in the presence of a series of ionic (sulphates, trimethyl ammonium bromides) and non-ionic (monoglycerides, maltosides) short (12 carbon atoms) and long (16 carbon atoms) n-alkyl chain surfactants. With the exception of the alkyl ammonium bromides, all of the short chain surfactants lower the pasting temperature (PT) in normal wheat starch, while the long chain surfactants have the opposite effect. Contrary, regardless of their chain length, all ionic surfactants lower the PT in waxy wheat starch while the non-ionic surfactants induce small, sometimes almost negligible changes in the PT. Calorimetric studies revealed the absence of a direct connection between the effect of surfactants on the onset of the starch gelatinization transition and the PT. However, in the presence of all surfactants, except the alkyl ammonium bromides, the PT of normal wheat starch was found to lie within or very close the temperature range within which the dissociation of the amylose-surfactant complexes takes place. Waxy wheat starch, in contrast, pasted at temperatures that fell within the temperature range of the starch gelatinization transition. This is taken as evidence of the existence of a correlation between the PT and the dissociation of the amylose-surfactant complexes.
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| 19. |
- Mira, I, et al.
(författare)
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On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. Part II. A confocal laser scanning microscopy study
- 2007
-
Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 68, s. 637-646
-
Tidskriftsartikel (refereegranskat)abstract
- The location and penetration patterns of two fluorescently-labelled, surface active molecules into normal and waxy wheat starch granules prior, during and after the temperature-induced gelatinisation were studied by means of confocal laser scanning microscopy (CLSM). Amphiphilic dyes were found to have a tendency to penetrate wheat starch granules in aqueous suspension. The penetration patterns were however found to be dependent on the contact time, type of starch and the chain length of the amphiphilic dye. The penetration of amphiphilic dyes through the starch granule matrix proved to be less restricted in waxy than in normal wheat starch. For a given type of starch, the penetration of the longer chain dye was more constrained than that of the shorter chain one. The extent to which the dye diffuses into the granule matrix as it gelatinizes is also affected by the chain length of the dye, diffusion of the shorter chain dye occurring more profusely and at lower temperatures than for the longer chain one. These differences are suggested to be related to the dissociation temperature of the AM-amphiphilic dye complexes.
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| 20. |
- Nacos, M.K., et al.
(författare)
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Kenaf xylan – A source of biologically active acidic oligosaccharides
- 2006
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 66:1, s. 126-134
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Tidskriftsartikel (refereegranskat)abstract
- Two xylose-rich hemicellulose fractions were obtained from kenaf wood (Hibiscus cannabinus L.) through a series of sequential extractions which dissociated xylans from other cell wall components. These fractions were subsequently used as substrates for the production of biologically active aldouronic acids. Incubation of the xylans with a family 10 Thermoascus aurantiacus endoxylanase resulted in the isolation of an aldotetrauronic acid as the main acidic oligosaccharide in the hydrolysis products. Enzymic hydrolysis with a family 11 Sporotrichum thermophile endoxylanase instead resulted in the isolation of a aldopentauronic acid as the main acidic oligosaccharide. The identity and purity of both xylans and aldouronic acids were assessed with solid-state FT-IR, solid-state and solution 13C NMR spectroscopy.
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