| 1. |
- Nuzzo, Marine, et al.
(författare)
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Confocal Raman microscopy for mapping phase segregation in individually dried particles composed of lactose and macromolecules
- 2015
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 481, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- The quality of powder is determined by its functionality such as dissolution, encapsulation and flowability. The functionality of powder is in turn determined by their primary properties such as morphology and composition which need to be studied. Hence morphology and surface composition has been largely investigated in spray dried powders and individually dried particles. On the contrary, there is only scarce information regarding the internal structure. With the aim of acquiring a better understanding of the localization of different ingredients in spray dried powders we have used confocal Raman microscopy to investigate the internal microstructure of individually dried particles. In this study three different macromolecules have been investigated: bovine serum albumin, hydroxypropyl methyl cellulose, and triblock co-polymer poloxamer in a lactose matrix are compared at various macromolecule to lactose ratios. The surface and internal component distribution in response to the macromolecule concentration has been established. For the first time phase segregation in particles during a short drying time range is shown. Macromolecules were enriched at the surface of the dried particles and a macromolecule depleted layer was observed below the surface. Macromolecule enriched domains were found segregated from the amorphous lactose matrix in the internal part of the particles. Confocal Raman microscopy was found to be a powerful tool for internal mapping in individually dried particles.
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| 2. |
- Nuzzo, Marine
(författare)
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Microstructure of spray dried particles at different scales of drying
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spray drying is a preferred method to produce dry powder of thermally sensitive materials such as food and pharmaceuticals. Drying conditions and formulation determine primary properties such as morphology and composition that finally provide functionality such as dissolution, encapsulation and flowability. Even though spray drying is a well-established method to produce dry powder numerous challenges are still encountered before we have a full understanding of the process. Indeed, the droplets undergo fast water evaporation, dimensional changes and temperature changes. It has previously been shown that adsorption of macromolecules at the droplet surface and phase segregation can occur while drying which will influence the particle properties. The first objective of this work was to provide a deeper understanding on how the surface morphology of powder particles depends on the surface properties of the components. The second objective was to explore how the internal microstructural depends on key properties of the components. The third objective was to investigate how well the particle morphology, surface and internal microstructure in single particle drying can predict the corresponding properties in full scale spray drying. Three lactose-macromolecule (protein, poloxamer, modified cellulose) feeds were dried in a single particle dryer and in a laboratory spray dryer. The impact of the concentration of the polymer on the surface rheology of the feed was observed. The morphology, surface composition and internal composition of the dried particle were observed by scanning electron microscopy (SEM), X-ray electron microscopy (XPS), and confocal Raman microscopy. (Paper I and II). To further investigate the internal microstructure and phase separation a two polymer feed (modified cellulose and maltodextrin) was spray dried at various dryer scales and at different solids content and ratios. The internal morphology was studied by confocal Raman microscopy. (Paper III). To evaluate the influence of the droplet breakup on the microstructure different atomization speed and oil droplet size in an acacia gum, maltodextrin and sunflower oil emulsion was spray dried. The characteristics of the powder were analyzed by LV-SEM and confocal Raman microscopy. (Paper IV). The aim of the last study was to reveal the morphology and internal microstructure correlation of whole milk powder spray dried in a single particle dryer, laboratory dryer, pilot plant dryer and a full scale dryer. LV-SEM imaging and confocal Raman microscopy were the techniques used to characterize these particles. (Paper V). The results show that interfacial properties of the components in the formulation can explain the dried particle morphology, although other factors such as the drying conditions and feed concentration also play a role. Particle surface composition is found to be influenced by the adsorption rate of macromolecules in the liquid feed. Even though spray drying is a fast drying process we found that ingredients can phase separate while drying. Further, although the particle size and drying time differs, analogies in individually dried particles, laboratory dried particles, pilot plant dried particles and full scale dried particles were found in terms of powder morphology, surface composition and internal composition.
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| 3. |
- Nuzzo, Marine, et al.
(författare)
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Phase segregation in individually dried particles composed of biopolymers
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:40, s. 10946-10954
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Tidskriftsartikel (refereegranskat)abstract
- Mixing of two biopolymers can results in phase separation due to their thermodynamically incompatibility under certain conditions. This phenomenon was first reported when the solution was allowed to equilibrate, but it has later been observed also as a consequence of drying. The challenges of this study were to observe phase segregation by confocal Raman microscopy and LV-SEM on dried film, individually dried particles, and spray dried particles. The influence of the solid content and the phase ratio (composition) of a HPMC/maltodextrin mixture on the localization of the ingredients in the individually dried particles was investigated. We observed that phase segregation of HPMC and maltodextrin is induced by solvent evaporation in film drying, single particle drying, as well as spray drying. The phase ratio is an important parameter that influences the localization of the HPMC-enriched phase and maltodextrin-enriched phase, i.e., to the particle surface, to the core, or in a more or less bicontinuous pattern. The drying time, affected by the solids content, was found to control the level of advancement of the phase segregation.
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| 4. |
- Nuzzo, Marine, et al.
(författare)
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Surface Composition and Morphology of Particles Dried Individually and by Spray Drying
- 2015
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Ingår i: Drying Technology. - : Informa UK Limited. - 1532-2300 .- 0737-3937. ; 33:6, s. 757-767
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates how the morphology of spray-dried particles is related to the formulation and properties of the components in the formulation. Further, the scale effects in comparisons of levitation-dried single particles and spray-dried particles in a lab-scale spray dryer have been addressed. The Drying Kinetics Analyzer (TM) generates single particles from a levitated drop under simulated spray-drying conditions. A set of surface-active polymers (bovine serum albumin, hydroxypropyl methyl cellulose, and triblock co-polymer Poloxamer), in combination with lactose, were analyzed for their dynamic surface properties in solution, and their effect on particle morphology and surface composition were determined by low-vacuum SEM and XPS analyses. The morphology obtained in spray drying was reproduced in the single-particle drying. The surface compositions were also similar, but higher levels of surface-active materials were found at the surface of the single particles as compared to the spray-dried particles. Further, the adsorption rate of surface-active compounds at the drop surface estimated by dynamic surface tension was found to be an important parameter to estimate the surface composition at different drying scales. The particle morphology was primarily determined by the surface rheological properties of the feed solution and, to a lesser extent, by the surface composition.
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