Heike P. Schuchmann

Emulsification in High-Pressure Homogenizers

High‐pressure homogenizers are frequently employed for the homogenization of low‐viscosity emulsions containing a proportion of disperse phase which is not too high. High‐pressure homogenizers essentially consist of a high‐pressure pump and a homogenizing nozzle. The design of the homogenizing nozzle influences the flow of the emulsion in the nozzle itself and hence the results of droplet disruption. It is shown which mechanism in frequently used homogenizing nozzles is usually responsible for disruption. Experimental results reveal the effects of the dispersed phase content and the viscosity of the disperse and continuous phases in different nozzles. The results can be explained on the basis of the mechanisms of disruption. Finally, the homogenizing nozzles presented are directly compared with one another.

Influences of Drying and Storage of Lycopene-Rich Carrots on the Carotenoid Content

ABSTRACT The stability of β-carotene and lycopene was investigated during convective air and inert gas drying, microwave vacuum drying, and freeze-drying for lycopene containing carrots (Daucus carota L. cv. Nutri Red). After convection drying at temperatures below 70°C, β-carotene and lycopene contents remained unchanged independent of the drying medium. Freeze-drying did not show any advantage to convection-drying regarding carotenoid retention. Microwave vacuum–drying led to dry products with high carotenoid retention within very short drying times of about 2 h. Storage in air and in inert gas (nitrogen) containers was studied for convection-dried products, observing a better retention of carotenoids when using inert gas for a period of up to 6 months. After convection- and microwave vacuum–drying, an even better carotenoid extractability could be observed. No changes in the isomere fractions could be detected in any case.

In vitro toxicity of amorphous silica nanoparticles in human colon carcinoma cells

Abstract The use of nanostructured silica (SiO2) particles is no longer restricted to biomedical and (bio-) technological fields but rather finding applications in products of the food industry. Thus, our studies on the toxicological relevance of SiO2 nanoparticles focused on cytotoxic effects, the modulation of the cellular redox status and the impact on DNA integrity in human colon carcinoma cells (HT29). The results indicate that these SiO2 nanoparticles stimulate the proliferation of HT29 cells, depending on the incubation time and the particle size. The cytotoxicity of the investigated SiO2 nanoparticles was found to depend on the concentration, size and on the FCS content of the culture medium. Furthermore, SiO2 seem to interfere with glutathione biosynthesis. The results indicate further that effects of SiO2 NPs are not mediated by oxidative stress but by interference with the MAPK/ERK1/2 as well as the Nrf2/ARE signalling pathways. Additionally, investigations regarding DNA integrity revealed no substantial (oxidative) DNA damage.

Stability of anthocyanin-rich w/o/w-emulsions designed for intestinal release in gastrointestinal environment.

Anthocyanins belong to the most important hydrophilic plant pigments. Outside their natural environment, these molecules are extremely unstable. Encapsulating them in submicron-sized containers is one possibility to stabilize them for the use in bioactivity studies or functional foods. The containers have to be designed for a target release in the human gastrointestinal system. In this contribution, an anthocyanin-rich bilberry extract was encapsulated in the inner aqueous phase of water-in-oil-in-water-double emulsions. The physical stability as well as the release of free fatty acids and encapsulated, bioactive substances from the emulsions during an in vitro gastrointestinal passage were investigated. The focus was on the influence of emulsion microstructural parameters (for example, inner and outer droplet size, disperse phase content) and required additives (emulsifier systems), respectively. It could be shown that it is possible to stabilize anthocyanins in the inner phase of double emulsions. The release rate of free fatty acids during incubation was independent of the emulsifier used. However, the exterior (O/W)-emulsifier has an impact on the stability of multiple emulsions in gastrointestinal environment and, thus, the location of release. Long-chained emulsifiers like whey proteins are most suitable to transport a maximum amount of bioactive substances to the effective location, being the small intestine for anthocyanins. In addition, it was shown that the dominating release mechanism for entrapped matter was coalescence of the interior W(1) -droplets with the surrounding W(2) -phase.

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.

Evaluation of Long Term Stability of Model Emulsions by Multisample Analytical Centrifugation

Emulsion-based products are found within the chemical and agrochemical, cosmetic, pharmaceutical, and food industries. As emulsion structures are thermodynamically unstable, shelf-life stability is a main aspect in product and process development. The objective of this work was to evaluate multisample analytical centrifugation with STEP-technology as an accelerated test for predicting the long-term stability of emulsions. Therefore, model emulsions were designed that exhibited creaming, coalescence, flocculation, and Ostwald ripening as the dominating instability mechanism.

Production of W/O/W (water-in-oil-in-water) multiple emulsions: droplet breakup and release of water.

We investigate breakup of W/O/W double emulsion droplets at high viscosity ratios and coalescence of inner water droplets dependent on the dispersed phase content (DPC) of the inner emulsion. The rheological analyses of the inner emulsions confirm the behavior expected from literature - increasing viscosity with increasing DPC and elastic behavior for high DPC. The resulting droplet sizes seem to be influenced only by the viscosity ratio calculated using the viscosity of the inner emulsion. An influence of the elastic properties of the inner emulsions could not be observed. Moreover, breakup of double emulsion droplets seems to follow the same rules as breakup of Newtonian droplets. In the second part of the paper we focus on the release of water from double emulsions by coalescence. A direct correlation between resulting double emulsion droplet sizes and encapsulation efficiency was found for each system. The initial inner dispersed phase content has a big influence on the release rate. This can partly be explained by the influence of the dispersed phase content on collision rate. Moreover, it was found that for high internal phase concentrations inner droplets coalesce with each other. The so formed bigger inner droplets seem to increase the overall release rate.

Food Engineering at Multiple Scales: Case Studies, Challenges and the Future—A European Perspective

Abstract A selection of Food Engineering research including food structure engineering, novel emulsification processes, liquid and dry fractionation, Food Engineering challenges and research with comments on European Food Engineering education is covered. Food structure engineering is discussed by using structure formation in freezing and dehydration processes as examples for mixing of water as powder and encapsulation and protection of sensitive active components. Furthermore, a strength parameter is defined for the quantification of material properties in dehydration and storage. Methods to produce uniform emulsion droplets in membrane emulsification are presented as well as the use of whey protein fibrils in layer-by-layer interface engineering for encapsulates. Emulsion particles may also be produced to act as multiple reactors for food applications. Future Food Engineering must provide solutions for sustainable food systems and provide technologies allowing energy and water efficiency as well as waste recycling. Dry fractionation provides a novel solution for an energy and water saving separation process applicable to protein purification. Magnetic separation of particles advances protein recovery from wastewater streams. Food Engineering research is moving toward manufacturing of tailor-made foods, sustainable use of resources and research at disciplinary interfaces. Modern food engineers contribute to innovations in food processing methods and utilization of structure–property relationships and reverse engineering principles for systematic use of information of consumer needs to process innovation. Food structure engineering, emulsion engineering, micro- and nanotechnologies, and sustainability of food processing are examples of significant areas of Food Engineering research and innovation. These areas will contribute to future Food Engineering and novel food processes to be adapted by the food industry, including process and product development to achieve improvements in public health and quality of life. Food Engineering skills and real industry problem solving as part of academic programs must show increasing visibility besides emphasized training in communication and other soft skills.

Differential scanning calorimetry (DSC) in multiple W/O/W emulsions

Multiple water-in-oil-in-water (W/O/W) emulsions offer a huge potential as encapsulation systems in different food, cosmetic, and pharmaceutical applications. Because of their complex structure, however, it is difficult to characterize these systems. Typical measurement techniques to determine the size and stability of the inner water droplets encapsulated in the oil droplets show limitations and inaccuracies. Determining the total amount of water in the inner droplets is most often done by indirect methods to date. We describe an analytical method based on differential scanning calorimetry (DSC) for characterizing the total amount of encapsulated water droplets and their stability in W/O/W multiple emulsions. It uses the possibility to directly determine the latent heat of freezing of water droplets of the same size and composition as in the multiple emulsions. The amount of water in the inner droplets of a W/O/W emulsion can thus be calculated very accurately. It is shown that this method enables furthermore detecting multi-modalities in the size distribution of inner water droplets in W/O/W emulsions. Changes in droplet size distribution of the inner droplets occurring during the second emulsification step of processing or during storage can be detected. DSC thus offers a powerful tool to characterize the structure of multiple W/O/W emulsions.

Effect of Molecular Weight Reduction, Acetylation and Esterification on the Emulsification Properties of Citrus Pectin

Citrus pectin was chemically and thermally modified in order to increase the hydrophobic character of the molecule and its adsorptivity to the oil–water interface. The degree of acetylation and methylesterification was increased and the molecular weight was reduced. The emulsion formation and stabilization properties of these modified pectins were evaluated by surface and interfacial tension measurements and emulsification experiments. For the production of emulsions, a high pressure homogenizer was used. The viscosity ratio between oil and emulsion phase was adjusted by varying the amount of added sucrose. Pectins with a higher degree of methylesterification (DE) decrease the interfacial tension significantly compared to the unmodified pectin. Pectins with increased degree of acetylation (DAc), however, show higher interfacial tension values. In emulsification experiments, pectins with a reduced molecular weight do neither significantly reduce droplet sizes nor improve emulsion stability. Pectins with increased DE or DAc reduce the Sauter mean diameter d3,2 of emulsions significantly and, in case of an DE increase, also show excellent long term stability. Their performance is also superior to sugar beet pectin under comparable experimental conditions.