Heike Karbstein

Developments in the continuous mechanical production of oil-in-water macro-emulsions

Abstract Emulsification processes are determined both by droplet disruption and droplet re-coalescence. This paper explains the fundamentals of droplet disruption in laminar and turbulent flow. Emulsification results from different continuous emulsification machines are compared with respect to the energy density (specific volumetric energy input) achieved. This is the first time that such a comparison has been made for both droplet disruption itself and droplet disruption superimposed by re-coalescence.

Adsorption kinetics of emulsifiers at oil—water interfaces and their effect on mechanical emulsification

Abstract The bursting membrane method of measuring the adsorption of emulsifier molecules at oil—water interfaces is presented. For the emulsifiers dodecyl alcohol-10-glycol ether, a whey protein concentrate and egg yolk the adsorption kinetics are measured. It is shown that this method is applicable to determine the adsorption kinetics. Oil—water emulsions have been prepared with the above-mentioned emulsifiers. The influence of the adsorption kinetics of these emulsifiers on the emulsification result is shown.

Structure stability and crystallization behavior of water in oil in water (WOW) double emulsions during their characterization by differential scanning calorimetry (DSC)

Water in oil in water (WOW) double emulsions are of great interest for the encapsulation of valuable substances. Nevertheless, the stabilization against inner water loss is still a challenging issue that impedes systematical research on the impact of the formulation. One common and applied technique to characterize the amount of inner water encapsulated in double emulsions is based on differential scanning calorimetry (DSC). Thereby, WOW double emulsions are frozen and thawed according to a defined method and afterward the amount of encapsulated water is calculated based on the DSC measurement result. For systematical investigations on the formulations’ impact on the encapsulation efficiency (EE), structure stability during this freezing and thawing procedure is required to be independent of formulation changes, whereby the EE is defined as the ratio between the amount of inner water after a specific time and the initial amount of water used for preparation of the double emulsion. In this study, we focused on the structural stability of double emulsions during their characterization by DSC. We prepared WOW double emulsions with varied formulations and characterized them considering inner and outer droplet size distribution (laser diffraction), microstructure (microscope), and EE (DSC). In some cases, the EE values determined by DSC were not reproducible and contradicted microscopic pictures and measured droplet size distributions. By using a polarizing microscope with temperature-controlled sample chamber, structure changes during the freezing and thawing procedure could be observed. Contact-induced crystallization, water diffusion as well as the spread of the phase transition temperature are discussed as reasons for the barely reproducible and sometimes contradictory results. Based on our findings, it is recommended for further studies on double emulsions to examine the structure stability during the DSC measurements.

Serial combination drying processes: A measure to improve quality of dried carrot disks and to reduce drying time

ABSTRACT Conventional drying processes like hot air-drying (HAD), freeze-drying (FD) and microwave vacuum drying (MVD) have specific advantages and disadvantages concerning product quality and drying time. Recent studies have shown that serial combinations of these processes can lead to better product quality (water content, color, hardness, rehydration, volume, and ingredient retention) and favorable process parameters (shorter time, less energy consumption). However, little is known about the timing of the changeover point between the different processes. In this study, we investigated the development of quality parameters (volume retention, rehydration properties) during FD, HAD, and MVD either as a single or as a serial combination process with varying changeover point. Therefore, carrot disks were processed in a modular drying processor to different final relative moisture contents. On this basis, recommendations were derived for certain combinations of drying processes to achieve desired product quality parameters, partially with shorter drying times.

Fabrication of Nanoemulsions by Rotor-Stator Emulsification

Abstract Rotor-stator emulsification devices are versatile tools for the production of fine emulsions in various industrial sectors. These devices are particularly useful when high viscous emulsions need to be processed and when emulsifiers with slow adsorption kinetics are used. In these cases, rotor-stator devices are capable of generating much smaller droplets than, e.g., high-pressure homogenizers. This chapter presents different rotor-stator devices for batch and continuous processes, such as high-shear mixers, disperser discs, colloid mills, and in-line gear-rim devices, and outlines possible modes of operation. Furthermore, basic concepts are explained that help to manipulate the emulsion droplet size generated in rotor-stator devices. Different process and formulation parameters and how they influence the emulsion droplet size are discussed in detail to optimize emulsion processes toward nanoemulsion production. Finally, examples of successful nanoemulsion preparation by rotor-stator devices are given.