Crystallization in Emulsions: A Thermo-Optical Method to Determine Single Crystallization Events in Droplet Clusters

Delivery systems with a solid dispersed phase can be produced in a melt emulsification process. For this, dispersed particles are melted, disrupted, and crystallized in a liquid continuous phase (melt emulsification). Different to bulk crystallization, droplets in oil-in-water emulsions show individual crystallization behavior, which differs from droplet to droplet. Therefore, emulsion droplets may form liquid, amorphous, and crystalline structures during the crystallization process. The resulting particle size, shape, and physical state influence the application properties of these colloidal systems and have to be known in formulation research. To characterize crystallization behavior of single droplets in micro emulsions (range 1 µm to several hundred µm), a direct thermo-optical method was developed. It allows simultaneous determination of size, size distribution, and morphology of single droplets within droplet clusters. As it is also possible to differentiate between liquid, amorphous, and crystalline structures, we introduce a crystallization index, CIi, in dispersions with a crystalline dispersed phase. Application of the thermo-optical approach on hexadecane-in-water model emulsion showed the ability of the method to detect single crystallization events of droplets within emulsion clusters, providing detailed information about crystallization processes in dispersions

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

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

Verarbeitungseigenschaften und gesundheitliche Qualität von industriell hergestellten Möhrensäften aus ökologisch erzeugten Möhren

Die Eignung aus Japan stammender Möhren (Daucus carota L. var. Nutri Red) für ökologischen Anbau und Bio-Saftherstellung nach gewerblichen/industriellen Standardverfahren wurde im Rahmen des Projektes geprüft. Diese Möhren enthalten das gesundheitsfördernde Carotinoid Lycopin, das sonst fast ausschließlich in Tomaten vorkommt. Die Carotinoidgehalte der frischen Möhren (Lycopin, Beta-Carotin, Phytoen, Phytofluen) bleiben während der Saftherstellung nach einem Standardverfahren weitgehend erhalten; cis-Isomere des Lycopins entstehen nicht. Wasserlösliche Inhaltsstoffe mit einem hohen antioxidativen Potential und damit möglicherweise gesundheitsfördernder Wirkung reichern sich im Saft an. Aus ökologisch erzeugten Nutri Red-Möhren kann damit ein ernährungsphysiologisch hochwertiger Bio-Saft erzeugt werden. Aus einem vom Projektpartner Fruchtsaft Bayer & Co. produzierten Direktsaft wurde vom Projektpartner Haus Rabenhorst ein marktfähiger Prototyp entwickelt, der als "Bio-Lycopin-Möhrensaft" im Rahmen einer Marktanalyse zur Zeit in Apotheken, Reformhäusern und im Naturkosthandel angeboten wird. Ein erheblicher Anteil der gesundheitsfördernden Carotinoide wird während der Saftherstellung nach Standardverfahren im nicht weiter verwertbaren Pressrückstand angereichert. Untersuchungen im Labormaßstab haben gezeigt, dass zellgewebemodifizierende Enzyme den Carotinoidgehalt der Säfte durch Nutzung der "Reserven" im Pressrück-stand erheblich steigern können. Kritisch ist die optimale Durchmischung einer En-zymkombination aus jeweils 10 g Zellulase und Pektinase je kg Möhrenmaische z.B. durch Verdünnung mit vorab hergestelltem Möhrensaft. Neben den mit über 50 % deutlich höheren Carotinoidgehalten wird mir diesem Verfahren gleichzeitig die Saftausbeute um ca. 10 % gesteigert. So erzeugter Saft enthält je kg 70 mg all-trans-Lycopin, 40 mg all-trans-Beta-Carotin und insgesamt 125 mg Carotinoide. Die Verfahrensübertragung in den Pilotmaßstab sollte wiederholt werden

Impact of effervescent atomization on oil drop size distribution of atomized oil-in-water emulsions

In this work the application of effervescent atomization to spray drying of food liquids like emulsions is explored. Therefore the influence of the atomization process on the breakup of oil drops inside the emulsion is investigated. It is expected that the oil drop size distribution of the emulsion is influenced by the stress inside the nozzle orifice and the following atomization. According to Grace the viscosity ratio between disperse and continuous phase is a crucial factor for drop breakup. A model oil-in-water emulsion was used. The viscosity of the continuous phase was adjusted by adding maltodextrin or gelatinized corn starch thus varying the viscosity ratio in the range between 15 and 0.1. The dry matter content and corresponding viscosity show only low influence on the spray drop size distribution. However, the atomized emulsions contain mostly smaller oil drops compared to the original emulsions. The influence of the atomization on the oil drop size distribution decrease with decreasing viscosity ratios. An influence of increasing stress due to increased atomization gas mass flow is present but less significant. The viscosity ratio thus allows controlling the influence of the atomization on the oil drop size distribution in the spray. The invariance of the spray drop size distribution on minor changes in fluid properties like viscosity is a favorable characteristic in food processing where such changes are common

Surfactant Concentration Regime in Miniemulsion Polymerization for the Formation of MMA Nanodroplets by High-Pressure Homogenization

This article focuses on the adequate surfactant concentration regime in which MMA droplets are stabilized sufficiently against coalescence during high-pressure homogenization but still no diffusion processes from droplets to micelles take place in the polymerization. Monomer miniemulsions with different surfactant concentrations were prepared with different energy inputs. Emulsions result that depend either on the surfactant concentration or on the energy input of the homogenization process. For both cases, the occupancy of the interface is compared as a function of the droplet size. It is shown that the surfactant concentration needed for the stabilization of a specified interface area decreases with increasing droplet size. For the dependence of droplet size on the energy input, it is shown that more surfactant can be applied before emulsion polymerization starts, but the applicable surfactant concentration is lower than the cmc and also depends on droplet size

Infrared spectroscopy of bilberry extract water-in-oil emulsions: Sensing the Water-Oil Interface

Water-in-oil (w/o) emulsions are of great interest in many areas of the life sciences, including food technology, bioprocess engineering, and pharmaceuticals. Such emulsions are complex multi-component systems and the molecular mechanisms which lead to a stable emulsion are yet to be fully understood. In this work, attenuated total reflection (ATR) infrared (IR) spectroscopy is applied to a series of w/o emulsions of an aqueous anthocyanin-rich bilberry extract dispersed in a medium chain triglyceride (MCT) oil phase. The content of the emulsifier polyglycerin-polyricinoleat (PGPR) has been varied systematically in order to investigate whether or not its concentration has an impact on the molecular stabilization mechanisms. The molecular stabilization is accessed by a careful analysis of the IR spectrum, where changes in the vibrational frequencies and signal strengths indicate alterations of the molecular environment at the water/oil interface. The results suggest that adding emulsifier in excess of 1% by weight does not lead to an enhanced stabilization of the emulsion

Effect of Atomizer Geometry and Rheological Properties on Effervescent Atomization of Aqueous Polyvinylpyrrolidone Solutions

The investigated effervescent atomizer is a special type of internal mixing pneumatic atomizer with a significantly reduced atomization gas consumption compared to conventional external mixing pneumatic atomizers. First the concentration influence of aqueous polyvinylpyrrolidone (PVP) solutions of concentrations from 15 to 45 % on the spray drop size distribution was investigated. As a significant increase in Sauter mean diameter and distribution width was only observed for concentrations above 40 % a change in breakup mechanism is assumed. This assumption is supported by the fact that also the improved model of Lund failed in the prediction of drop size at these concentrations. An essential challenge is the large width of the spray drop size distribution which is assumed to be connected to the spray pulsation. Therefore, the influence of nozzle orifice elongation and gas injection hole diameter reduction were investigated. Both depict no significant influence on Sauter mean diameter itself but reduced the standard deviation of Sauter mean diameter and the standard deviation of the distribution width enhancing thus the reproducibility of the spray characteristics. Also, reduction of the gas injection hole diameter reduced slightly the width of the distribution itself. The pulsation frequency of the spray was measured by high frequency laser diffraction spectroscopy. Nozzle orifice elongation and gas injection hole diameter reduction increased both the pulsation frequency as well as an increasing air-liquid mass ratio. The actual impact of the pulsation on the drop size distribution was not investigated in this work but will be future subject

Modeling of drop sizes from effervescent atomization of gelatinized starch suspensions

The applicability of previously published models for prediction of representative drop sizes resulting from effervescent atomization has been evaluated for usage with gelatinized starch suspensions. The calculated results are in qualitative agreement with experimental ones, but show an over prediction and reduced sensitivity to material properties. Analysis of the models shows that the material properties are neglected in a significant step