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| 2. |
- Elversson, J, et al.
(författare)
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Droplet and particle size relationship and shell thickness of inhalable lactose particles during spray drying
- 2003
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Ingår i: Journal of Pharmaceutical Sciences. - : Wiley. - 0022-3549 .- 1520-6017. ; 92, s. 900-910
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Tidskriftsartikel (refereegranskat)abstract
- To find means of controlling the size and density of particles intended for inhalation the relationship between droplet and particle size during spray drying was investigated. Lactose solutions were atomized with a two-fluid nozzle and dried in a laboratory spray drier. The effects of nozzle orifice diameter, atomization airflow and feed concentration on droplet and particle size were examined. Mass median diameter of both droplets and particles were analyzed with laser diffraction. In addition, scanning electron microscopy and transmission electron microscopy were used for studies of particle shape and morphology. It was demonstrated that nozzle orifice diameter and airflow, but not feed concentration controlled the droplet size during atomization. Increasing droplet size increased particle size but the effect was also influenced by feed concentration. Particles from solutions of a low concentration (1% w/w) were smaller than those from higher concentrations (5-20% w/w). This may be partly explained by lower yields at higher feed concentrations, but may also be related to differences in drying rate. Spray-dried lactose solutions formed hollow particles, and it was suggested that the shell thickness of the particles increased with increasing feed concentration
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| 3. |
- Millqvist-Fureby, Anna, et al.
(författare)
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An aqueous polymer two-phase system as carrier in the spray-drying of biological material
- 2000
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 225, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- This investigation describes a novel concept in formulation of carrier systems for spray-drying of biological materials. As carrier materials a system composed of poly (vinyl pyrrolidone) (PVP) and dextran was used. This system yields an aqueous two-phase system in which each phase is enriched in one of the polymers. By varying the composition of the system, the effective structure of a 'stirred' such system can be varied, covering the entire range from dextran continuous to PVP continuous. This facilitates encapsulation of either of these polymers in a spray-drying operation. In an attempt to investigate the spray-drying from such a system, the surface composition of the spray-dried powder obtained from various compositions of the two-phase system was analysed by electron spectroscopy for chemical analysis (ESCA), providing information on the distribution of the polymers in the powder and thus also in the spray droplets. The two-phase system was applied for spray-drying of live bacteria. The survival rate of the bacteria depended on the composition of the two-phase system. The storage stability of the bacteria in these formulations was investigated after storage at room temperature under dry conditions for four weeks, and it was found that the survival rate was 10-45%. The results therefore show that this type of formulation holds promise for future applications for micro-organisms as well as other sensitive biological materials such as proteins.
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| 4. |
- Millqvist-Fureby, Anna
(författare)
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Characterisation of spray-dried emulsions with mixed fat phases
- 2003
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Ingår i: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 31, s. 65-79
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Tidskriftsartikel (refereegranskat)abstract
- Fat encapsulation in spray-dried protein-stabilised emulsions is known to depend on the choice of protein, the emulsion droplet size, and the melting point of the fat. However, the fat encapsulation may also depend on the fat crystal habit. Fats may crystallise in three different α, ß' and ß, of which the ß-form is thermodynamically stable. The α-form is obtained in rapidly cooled fats, and it can then transform into the ß'-form during storage, and this crystal form is finally transformed into the ß-form. In order to investigate the effect of different fat phases on the spray-dried emulsions, two solid fats were studied: fully hardened rapeseed oil (ß-stable) and fully hardened palm oil (ß'-stable). The solid fats were used on their own or in mixtures with rapeseed oil, in order to provide fat phases with different properties. The emulsion composition was chosen as to mimic the composition of whole milk, i.e. 40% lactose, 30% sodium caseinate and 30% fat on a dry weight basis. The dried powders were stored under dry conditions at 4 or 37 °C in order to investigate the changes in the fat crystals and surface composition of the powders with time. The surface composition was analysed using electron spectroscopy for chemical analysis. Evaluation of the data showed that surface coverage of fat varied depending on the composition of the fat phase. The ratio of lactose to protein remained constant, which implies that the fat was present as `islands' on a surface composed of lactose and protein. The hardened palm oil crystallised initially in the α- or ß'-form (depending on the ratio of hardened fat to oil), and during storage, the crystal form gradually changed into the ß'-form. In powders containing hardened rapeseed oil only the stable ß-form was found, even in fresh samples. The surface coverage of fat was reduced after storage, whereas the ratio of lactose to protein at the surface remained unchanged. The emulsion droplet size in emulsions prepared at a low homogenisation pressure was considerably increased after spray-drying and reconstitution, whilst the emulsion droplet size was well preserved in emulsions prepared at high homogenisation pressure
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| 5. |
- Millqvist-Fureby, Anna, et al.
(författare)
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Surface composition of spray-dried milk protein-stabilised emulsions in relation to pre-heat treatment of proteins
- 2001
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Ingår i: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 21, s. 47-58
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Tidskriftsartikel (refereegranskat)abstract
- Several important technical properties of spray-dried food powders depend on particle-liquid interactions (e.g. wettability, dispersability) and particle-particle interactions (e.g. flowability). It can be assumed that the chemical composition of the surface layer of the particles to a large extent determine these properties. The present study has been aimed to investigate the relation between the surface composition of spray-dried milk protein-stabilised emulsions and pre-heat treatment of the proteins. Solutions of WPC were heat-treated at low (60-90°C) and high (140°C) temperature and the degree of denaturation was determined, prior to the preparation of emulsions with rapeseed oil. The surface composition of the dry powders were established by using ESCA (electron spectroscopy of chemical analysis).The emulsions were characterised by droplet size distribution before spray drying and after dissolution of the powders. Also free fat extractions and estimations of wettability (dissolution rates) were performed. The powder surface coverage of protein decreased with increasing degree of protein denaturation before the emulsification, whereas the emulsion droplet size increased both before spray drying and after reconstitution of powders. The free fat extraction as well as the dissolution rate, whereof the latter decreased with increasing surface fat coverage, correlated well with the fat coverage of the powder surface.
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