Untersuchungen über die physikalisch‐technischen Vorgänge beim Homogenisieren von Milch in Hochdruck‐Homogenisiermaschinen

2016

Processes

High-pressure homogenisation is a commonly used technique to produce emulsions with droplets in the micro to nano scale. Due to the flow field in the homogenizer, stresses are transferred to the interface between droplets and continuous phase. Cohesive forces within droplets interact with external stresses. To exceed the cohesive forces, high process pressures are necessary, which might cause a complex flow pattern and large flow velocities. Additionally, the pressure drop can induce cavitation. Inline measurements are a challenge, but necessary to understand droplet break-up in a high-pressure homogenizer. Recently, different optical methods have been used to investigate the flow conditions as well as the droplet deformation and break-up in high-pressure homogenisation, such as high speed imaging, particle and micro particle image velocimetry. In this review, those optical measuring methods are considered critically in their applications and limitations, achievable results and further developments.Keywords: high-pressure homogenisation; optical measurement methods; flow field characterisation; droplet break-up; emulsification MotivationHigh-pressure homogenisation (HPH) is widely used in chemical, pharmaceutical and food industry to produce emulsions with desired properties. Properties of emulsions, like mouth feel, colour, flow behaviour, or stability, depend strongly on their microstructure and thus on the droplet size distribution of the emulsion [1]. However, tailor-made adjustments of the droplet size distribution in emulsions is still challenging due to complexity of interactions of the process conditions and the properties of the formulation. In order to decrease the droplet size distributions, the volume-related energy density E v is increased, most often by increasing the pressure drop ∆p in the disruption unit [2]. Unfortunately, this might also lead to cavitation and cavitation-induced wear at the devices. A change in the homogeniser disruption unit design may also improve droplet breakup. As an example, Microfluidics ® offers so-called T-or Z-shaped disruption units which allow droplet size reduction well below <1 µm for specific formulations. Other manufacturers merchandise specific "energy-efficient" disruption units. Even when these disruption units work fine with some formulations, they do not with others. A deep understanding in the influence of disruption unit design and process parameters on flow patterns and resulting droplet sizes is still missing.One possibility to describe the influence of process conditions, and/or product recipe on resulting droplet sizes is to measure the average droplet size or the droplet size distribution (DSD) of the emulsion after homogenisation. Thus, the influence of different parameters like pressure drop [2][3][4][5], geometry of the device [2,6-9], or formulation [10][11][12][13] can be related to homogenisation efficiency, which allows some mechanistic insight into the high-pressure homogenisation process. However, offline measurements always repre...

Section: Visualisation Of Cavitation During the Hph Processsupporting

confidence: 87%

Section: Why Do We Need Detailed Information On the Hph Process?mentioning

confidence: 99%

Optical Measuring Methods for the Investigation of High-Pressure Homogenisation

Bisten

2016

Processes

“…This has implications particularly for the occurrence of cavitation [45,46]. The ratio of back-pressure and inlet pressure is defined as a Thoma number (Th) [46,47]. It is reported that cavitation decreases with increasing Th and disappears at Thoma numbers of 0.3 < Th < 0.5 [48].…”

Section: Inserting a Second Homogenization Stepmentioning

confidence: 99%

Extending Applications of High-Pressure Homogenization by Using Simultaneous Emulsification and Mixing (SEM)—An Overview

Gall

Runde²,

2016

Processes

Conventional high-pressure homogenization (HPH) is widely used in the pharmaceutical, chemical, and food industries among others. In general, its aim is to produce micron or sub-micron scale emulsions with excellent product characteristics. However, its energy consumption is still very high. Additionally, several limitations and boundaries impede the usage of high-pressure homogenization for special products such as particle loaded or highly concentrated systems. This article gives an overview of approaches that have been used in order to improve the conventional high-pressure homogenization process. Emphasis is put on the 'Simultaneous Emulsification and Mixing' process that has been developed to broaden the application areas of high-pressure homogenization.

“…In der Literatur existieren unterschiedliche Erklärungsansätze [Freudig, 2004] wie Mikroturbulenzen bzw. -jets [Bechtel, 1999], kritische Eigenschwingungen [Kurzhals, 1977] und Tropfenablösungen vom großen Tropfen [Behrend, 2002]. Weiterhin ist auch der Einfluss von Zweiphasengemischen wie Emulsionen auf die Kavitation noch nicht endgültig geklärt.…”

Section: Dimensionslose Beschreibungunclassified

“…Dass die Kavitation beim Emulgieren eine Rolle spielt, ist allerdings nachgewiesen [Riedel, 1973;Kurzhals, 1977;Karbstein, 1994;Behrend, 2002]. Riedel [1973] [Danner, 2001].…”

Section: Dimensionslose Beschreibungunclassified

Simultaneous Emulsification and Mixing

Köhler

Chemie Ingenieur Technik

2012

Das Hochdruckhomogenisieren ist heute eine weitverbreitete Technik in der chemischen, kosmetischen oder pharmazeutischen, aber auch der Erdöl‐ und Lebensmittelindustrie. Allerdings ist diese Technik immer noch wenig verstanden. Die Folgen sind schwer steuerbare Produktqualitäten und ein unnötig hoher Energieverbrauch. Die neu entwickelte simultane Emulgier‐ und Mischtechnik (SEM‐Technik) wird vorgestellt. Mit ihr ist es möglich, ein besseres Verständnis der einzelnen Teilvorgänge beim Hochdruckhomogenisieren, wie dem Zerkleinern und dem Stabilisieren, zu gewinnen und so den Prozess zu optimieren. Dies ermöglicht die Entwicklung neuer Prozesse und Produkte und Energieersparnisse von bis zu 90 %.