Aim of the present study was to investigate the impact of atomization and drying on the functionality of emulsions with a bilayered oil–water interface consisting of a globular protein (β-lactoglobulin, bLG) and anionic polysaccharides (pectins with varying degree of methoxylation). With regard to the atomization process, the emulsion spray droplet size generally decreased with increasing atomization energy. The spray droplet size distribution was narrower with rotary atomization compared to two-fluid nozzle atomization. The single droplet drying behaviour of the differently stabilized emulsions was similar as examined by acoustic levitation. With more than 95%, microencapsulation efficiency was high in all spray-dried particles. However, a shift in oil droplet size upon reconstitution indicated that oil droplet coalescence occurred within the process which was less pronounced in bilayer emulsions compared to the bLG-stabilised single layer emulsion. Data from interfacial viscoelasticity measurements showed distinct differences, which may explain oil droplet coalescence. The oxidative stability of encapsulated oil was influenced by both the physical state of the emulsions and the different constituents at the o/w-interface with bLG and low methoxylated pectin giving the best protection of the oil.

The aim of this study was to characterize the process of atomization and drying of layer-by-layer emulsions containing lecithin (single layer emulsion) and lecithin/chitosan (bilayer emulsion) and the oxidative stability of the microcapsules during storage. For this purpose, the analysis of the emulsion spray droplet size during two-fluid nozzle and rotary atomization was carried out to identify suitable process parameters. The drying behaviour of single and bilayer emulsions was investigated by calculation of the volume flow density during single-droplet drying during acoustic levitation. In spray-dried solid particles, the oxidative stability in the single layer microcapsules was higher than in the bilayer microcapsules. This was partly attributed to lower microencapsulation efficiency in the bilayer microcapsules compared to the single layer microcapsules. Furthermore, it could be shown, that excess chitosan in the bulk carrier matrix affects the free volume elements and thus oxygen diffusion.

Spray drying processes combine drying under mild conditions, formation of morphology, and shape forming in one process. These spray drying processes can be supplemented by another unit operation aiming at the production of the dry material, e.g. by polymerization. Since single droplets inside a spray are difficult to study, acoustic levitation is used as a model for spray polymerization. In this study the polymerization of the monomer N-vinyl-2pyrrolidone in levitated droplets was investigated. Competing processes of monomer consumption were observed by imaging and Raman spectroscopy. While the consumption by polymerization could only be monitored using Raman spectroscopy, the evaporation process could be observed by imaging as well as Raman spectroscopy. The results from Raman spectroscopy in conjunction with principal components analysis were backed up by image analysis. Because of bandwidth and memory limitations the image analysis was done offline. In order to reduce bandwidth and memory usage, an algorithm was developed that enables droplet features like surface area and volume to be measured online in a single pass. For this algorithm, a suited architecture was derived and implemented on the FPGA of a smart camera. The general feasibility of employing such a smart camera is demonstrated on images obtained by shadowgraphy during acoustic levitation.

During microencapsulation of sensitive (food) ingre dients by spray drying, one important step is the s pray drying process itself, which affects the emulsion droplet size distribution, the emulsion stability with rega rd to the oil droplet size as well as the structural integrity of the interface. The latter has a strong impact on t he encapsulation efficiency and the physical stability of reconstitu ted emulsions. By interfacial engineering the barri er properties and the packing density at the oil/water (o/w) inte rface can be modified. The interface can be enginee red by e.g. layer-by-layer-technology that involves sequential layering of polymers at the o/w-interface of an emu lsion via electrostatic interactions. By that means so-called multilayer emulsions can be obtained. Studies on t he characterization of these multilayer emulsions in relatio n t the spray drying process, especially with resp ect to the type of atomization and the drying behavior are lacking a d literature on the oxidative stability of spraydried multilayer emulsions is scarce. Scope Aim of the present study was to investigate the imp act of atomization and drying on the functionality of emulsions with a modified o/w interface consisting of b eta-lactoglobulin and pectins with varying degree o f methylation. Experimental Approach Beta-lactoglobulin and pectin (low and high methyla ted) were used for preparation of single and multil ayeremulsions containing fish oil. Electrostatic intera ctions were analyzed via zeta potential measurement s. Elasticity of emulsion interfaces was analyzed by droplet shap e analysis. The single droplet drying behavior was characterized by acoustic levitation. Spray droplet and oil droplet size distribution were measured by laser di ff action after two-fluid-nozzle and rotary atomization at differen t energy inputs. Spray drying was carried out at 18 0/70 °C inlet/outlet temperature. The morphology of the par ticles was analyzed by scanning electron microscopy . The oxidative stability of the fish oil was monitored v ia hydroperoxide and propanal content. Major results The single droplet drying behavior of the different ly stabilized emulsions was similar as examined by levitation. With regard to the atomization process, the emulsio n pray droplet size generally decreased with incre asing energy input to the atomizer. In two-fluid nozzle ato mization but not in rotary atomization, the spray d roplet size distribution was markedly influenced by the differe nc s in emulsion viscosity. The spray droplet size distribution was narrower with rotary atomization compared with two-fluid nozzle atomization. The oil droplet size of the emulsions was only slightly affected by the differe nt nergy inputs during atomization. However, in th e reconstituted state, the oil droplet size was higher than i n the original emulsions, which can be attributed t o coalescence. The oxidative stability of the oil was influenced b y oth the physical state of the emulsions and the diff rent constituents at the o/w-interface. For instance, in th e liquid state the oxidative stability was higher i n the original emulsions when compared to the reconstituted emulsi ons. Furthermore, the oxidative stability was affec ted by the type of pectin and thus the intensity of the oi l droplet charge. It can be assumed that in liquid an spray-dried emulsions, not only the particle charge but also th e constitution of the interface itself influences t he oxidative stability of encapsulated oil. * Corresponding author: yvonne.serfert@tu-berlin.de

Aim of the present study was to investigate the imp act of atomization and drying on the functionality of emulsions with an oil/water-interface (o/w-interface) c onsisting of beta-lactoglobulin (single layer emuls ion) and sequentially adsorbed pectins with varying degree of methylation at pH<pI (bilayer emulsions). Thus, the emulsion systems were characterized with respect to their be havior during atomization, their drying behavior in single droplet experiments and the oxidative stability of the dispersed phase (fish oil) during storage of li quid and spray-dried single and bilayer emulsions. The o/w-interface of the emulsions was predominantl y elastic, although the elasticity was higher in si gle layer emulsions compared to bilayer emulsions. The drying behavior of the different emulsions duri ng levitation of single droplets was similar. Regarding the atomization process, the emulsion spray droplet siz generally decreased with increasing energy input irrespective of the type of atomizer. With rotary atomization, the spray droplet size distribution of the different emulsion s was similar. The oxidative stability of the oil w as influenced by both the physical state of the emulsions and the diff rent constituents at the o/w-interface. In th e liquid state, the oxidative stability was higher in the original emulsions when compared to the reconstituted emulsi ons. The differences in oxidative stability in the spray-dri ed emulsions can partly be attributed to the microe ncapsulation efficiency, but also the physical characteristics o f the o/w-interface, which needs to be investigated in more detail.

Acoustic levitation was investigated as a model for spray processes. The influence of different parameters on the drying process of aqueous polyvinylpyrrolidone (PVP) solutions was studied and compared to the evaporation of water. The adequacy of acoustic levitation as model for spray processes was demonstrated. Experiments with water and aqueous PVP solutions indicated no dependency of the droplet size on the drying process for droplets with a diameter between 300 mm and 1.5 mm. Particles dried in an acoustic levitator displayed good accordance of morphology with those obtained in a spray tower. Surprisingly the addition of PVP to water resulted in faster evaporation of the solvent. Mathematical models of single droplets within a spray process typically refer to spherically symmetric droplet geometries. The simulation of other morphologies and their evolution throughout the process is still very challenging. A new drying model based on a fully three-dimensional meshfree approach is under development and shows good agreement to basic established models regarding the drying of a single droplet.

Aim of the present study was to characterize the pr ocess of atomization and drying of layer-by-layer emulsions containing lecithin (single layer emulsio n) and lecithin/chitosan (multilayer emulsion) and the oxidative stability of the spray-dried emulsions du ring storage. For this purpose, the analysis of the emulsion spray droplet size during atomization by two differ ent atomization devices, i.e. two-fluid nozzle and rotary atomizer, was carried out to identify suitable proc ess parameters. The drying behaviour of single laye r nd multilayer emulsions was investigated by single-dro p drying via calculation of the mass transfer durin g acoustic levitation. In spray-dried emulsions, the oxidative stability in the single layer emulsions w as higher than in the multilayer emulsion. This was partly a ttributed to a lower microencapsulation efficiency in the spray-dried multilayer emulsion compared to the spr ay-dried single layer emulsion. Furthermore, it cou ld be shown, that excess chitosan in the bulk carrier mat rix ffects the free volume elements and thus oxyge n diffusion.