| 1. |
- Andersson, Helene, 1983, et al.
(författare)
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Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films
- 2013
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 48:1-2, s. 240-248
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Tidskriftsartikel (refereegranskat)abstract
- Films of ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be used for extended release coatings in oral formulations. The permeability and microstructure of free EC/HPC films with 30% w/w HPC were studied to investigate effects of EC molecular weight. Phase separation during film spraying and subsequent HPC leaching after immersion in aqueous media cause pore formation in such films. It was found that sprayed films were porous throughout the bulk of the films after water immersion. The molecular weight affected HPC leaching, pore morphology and film permeability; increasing the molecular weight resulted in decreasing permeability. A model to distinguish the major factors contributing to diffusion retardation in porous films showed that the trend in permeability was determined predominantly by factors associated with the geometry and arrangement of pores, independent of the diffusing species. The film with the highest molecular weight did, however, show an additional contribution from pore wall/permeant interactions. In addition, rapid drying and increasing molecular weight resulted in smaller pores, which suggest that phase separation kinetics affects the final microstructure of EC/HPC films. Thus, the molecular weight influences the microstructural features of pores, which are crucial for mass transport in EC/HPC films.
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| 2. |
- Andersson, Helene, et al.
(författare)
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Effects of Molecular Weight on Phase Separated Coatings for Controlled Release of Drugs
- 2013
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Ingår i: Annual Transactions of the Nordic Rheology Society. ; , s. 249-
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Tidskriftsartikel (refereegranskat)abstract
- Phase separated films with controlled porosity were made from ethyl cellulose (EC) and 30% w/w hydroxypropyl cellulose (HPC). The molecular weight of EC can be used to modify the mass transfer rate through coatings by effects on microstructure of the film. Processing conditions are, however, affected by the solution rheology, which could influence the film quality when using different molecular weights.
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| 3. |
- Andersson, Helene, 1983, et al.
(författare)
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Extensional flow, viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids
- 2011
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 25:6, s. 1587-1595
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Tidskriftsartikel (refereegranskat)abstract
- Viscoelastic doughs of zein and starch were prepared at 40 degrees C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of beta-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume.
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| 4. |
- Ekberg, Olle, et al.
(författare)
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Flow properties of oral contrast medium formulations depend on the temperature
- 2010
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 51:4, s. 363-367
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Tidskriftsartikel (refereegranskat)abstract
- Background: During the therapeutic videofluoroscopic examination of swallowing, gradation of bolus volume, texture, and viscosity can be implemented to determine the optimal bolus characteristics in that particular patient. When a thickened liquid is given to a dysphagic patient it is served at room temperature. However, in these patients with a delayed oral and/or pharyngeal stage of swallow, the bolus is held for a long time in the oral cavity. The temperature of the thickened liquid thereby increases. Purpose: To study the rheological exploration (variation of viscosity with temperature) of thickened food used for radiologic swallowing examinations in patients with oral and pharyngeal dysfunction, in particular in mixtures of barium sulfate suspensions and in iodine solutions. Material and Methods: Deep-frozen mango purée was thawed at room temperature. It was then mixed with barium sulfate contrast medium to a density of 25% w/w. Resorce® Thicken Up was mixed at room temperature at two concentrations: 4.3% w/w (4.5 g thickener + 100 g distilled water) and 6.0% w/w (4.5 g thickener + 70 g distilled water). The thickener consisted of modified corn starch. Resorce® Thicken Up was also mixed at room temperature with two concentrations of an iodine contrast material, iohexol (Omnipaque®, 350 mg I/ml). The two concentrations were: 4.3% w/w (4.5 g thickener + 100 g iohexol) and 6% w/w (6 g thickener + 100 g iohexol). Measurements were carried out from 20°C to 37°C using a Stresstech HR rheometer. The rheometer was equipped with a concentric cylinder measuring system (inner cylinder 15 mm). Results: The samples containing thickener in water as well as in iohexol showed a dependence on thickener concentration and temperature. The mango purée with barium sulfate displayed very small temperature dependence. The thickener solutions in iohexol had significantly higher viscosity compared with the other thickener solutions and the mango purée. The relative decrease shows that mango purée, the 6% thickener solution in water, and solutions with iohexol exhibited similar relative viscosity change at different temperatures. Conclusion: Our conclusion is therefore that it is important always to make the solution with high precision. It is also of importance to observe how long the patient keeps the bolus in the mouth. This might vary and actually it may not be possible to influence this factor. When different types of thickeners are compared, it is important to take into account the temperature at which the thickener is observed.
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| 5. |
- Filli, Kalep, et al.
(författare)
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Development and characterization of extruded biodegradable foams based on zein and pearl millet flour
- 2011
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Ingår i: Annual Transactions the Nordic Rheology Society. ; 19, s. 139-145
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Konferensbidrag (refereegranskat)abstract
- The aim was to establish a preliminary processing window for extrusion foaming of blends of zein and pearl millet flour and to estimate the properties of the extrudates. The weight ratios of zein:pearl millet flour were 75:25, 72:28 or 70:30 and foamed extrudates with a circular geometry were produced with bulk densities between about 350 and slightly higher than 500 kg/m3. Compounds with a higher zein content tended to give a more foamed structure. The stiffness (modulus) in compression of the foams was in the range 25-50 MPa with higher values at a higher bulk density. At a given density, the specimens with a higher zein content appeared to give a stiffer structure.
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| 6. |
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| 7. |
- Gillgren, T., et al.
(författare)
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Impact of melt rheology on zein foam properties
- 2010
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 45:21, s. 5762-5768
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Tidskriftsartikel (refereegranskat)abstract
- Zein, the main protein fraction in maize, is left as a by-product from bio-ethanol production. The protein has been investigated as a material for a long time, but mainly in the form of films. In contrast, foamed zein is presented in this article. Zein foams may perhaps be used, e.g. as trays for biodegradable food packages or as scaffolds for tissue engineering. A batch method for manufacturing solid foams was successfully developed, the foams being manufactured by evaporation of solvent from zein resins. In order to be suitable for foam formation, a resin must possess gas-retaining properties, which can be predicted by extensional rheology. The presence of plasticizer in some of the resins decreased their extensional viscosity, and this in turn affected the foaming process. Although all the resins displayed strain-hardening behaviour, there was coalescence of pores in all the foams. Insufficient extensional viscosity resulted in the collapse of pore walls during foam expansion. Structure analysis showed, e.g. that most pores were elongated along the main axis of the mould in which the foams were manufactured. The plasticizer content in the resins had no significant effect on the mechanical properties of the foams.
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| 8. |
- Gillgren, T., et al.
(författare)
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Mechanical and Barrier Properties of Films from Millet Protein Pennisetin
- 2011
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Ingår i: Food Biophysics. - : Springer Science and Business Media LLC. - 1557-1858 .- 1557-1866. ; 6:4, s. 474-480
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Tidskriftsartikel (refereegranskat)abstract
- Plastics are one of the most commonly used materials today in an immense range of applications. Since plastics originate from petroleum, which is not a renewable resource, we need to find alternatives to achieve environmentally sustainable goals. One of our most abundant renewable resources is cereals; wheat gluten is recognized as a replacement for synthetic plastics. Another cereal protein is pennisetin from pearl millet, which can grow in more arid areas and is therefore an important crop in times of climate change. In contrast to gluten, the material properties of pennisetin have as yet been relatively unexplored. This work evaluated the mechanical and barrier properties of pennisetin films, including three different plasticizers (glycerol only, glycerol/citric acid mixture, and glycerol/lactic acid/polyethylene glycol mixture). The films were cast from ethanol solutions. It was found that all of the three plasticizers resulted in approximately equal thermomechanical properties in the pennisetin films. However, the glycerol/citric acid mixture seemed to give more beneficial tensile and barrier properties. The advantage of this plasticizer mixture was believed to be due to the altered microstructure of the films. The material properties of pennisetin were found to be fully comparable to those of other cereal protein materials.
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| 9. |
- Gillgren, T., et al.
(författare)
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Modulating rheo-kinetics of native starch films towards improved wet-strength
- 2011
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 83:2, s. 383-391
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Tidskriftsartikel (refereegranskat)abstract
- Starch directly functionalised in the plant by modulation of its biosynthesis by mutagenesis and transgene technology was exploited for its extended functionality beyond the normal variation In this study we investigated the theological and mechanical properties of films from such structurally highly different starch types derived from potato and cereal sources of normal and mutant and transgenic backgrounds A new improved technique was developed to permit the dynamic mechanical analysis of films in the presence of water It was found that the amylose content was decisive for the mechanical properties of the films - an increase in the amylose content resulted in both a higher stress and strain at break Interestingly there was no correlation between the speed of hydration and mechanical water resistance of the films Generally the films were clear and transparent even after wetting Transgenic potato starch with a low content of phosphate displayed an extraordinary combination of high robustness transparency mechanical strength and extensibility even in a wet condition The combination of optimal phosphate and amylose concentrations in this sample probably favoured hydration and amorphisation without compromising the inter-chain interactions of the polysaccharide network.
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| 10. |
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