Prof. Germann's Fluid Dynamics Group
Relationship between dough rheology and surface properties
Funding source: AiF 6472/15 N (in collaboration with Prof. Th. Becker)
A key step in the production of wheat flour dough is the kneading process. The purpose of this process is to develop the dough gluten network and bring air into the dough. While under-kneading results in dough with insufficient gas retention capacity, over-kneading destroys the gluten network. Over-kneading also leads to smaller water absorption capacity and impairs the dough’s ability to rise. The rheological characteristics of wheat flour dough are very important parameters for the evaluation of not only the wheat quality, but also the quality of the final product. As off-line rheological measurements involve an undesired time delay, such measurements are infeasible in practice. Therefore, the kneading process is currently controlled using visual and haptic information from experienced personnel. The goal of this project is to develop a simulation tool to predict the quality of bread during the kneading process. An improved damage function model will be employed to describe the dough matrix, whereas the air bubbles are described using a volume-of-fluid method. Information from laser scattering will be utilized to update the dynamic boundary conditions. The computational approach will be verified by correlating the rheological data (e.g., bulk porosity, surface properties) with the sensory characteristics of baked bread. Fig. 3 shows one of the mixing geometries examined in this project.
Fig. 1: Spiral-kneader geometry used for numerical simulations.
Rinsing and mixing phase generation of ultrafiltration spiral wound membranes after milk concentration
Funding source: AiF 6474/15 N (in collaboration with Prof. U. Kulozik)
Little is known about the mixing-phase generation of spiral wound membranes (SWMs) following the concentration of milk by ultrafiltration. SWMs are complex devices, and it is assumed that a thorough investigation of water consumption, milk loss, and time requirements will yield very useful insights in terms of options for the overall economical and ecologically sustainable optimization of membrane plants. In the food industry, hygienic conditions are to be maintained by frequent CIP cleaning. Therefore, product losses and water consumption add up to considerable amounts, especially since SWMs are difficult to rinse and clean. A schematic diagram of a SWM module is given in Fig. 4. The aim of this project is to assess the impacts of fluid distribution, fluid flow behaviour, and the technical characteristics of the SWMs and the processing conditions on the amount of mixing phase, i.e., water and time consumption and milk losses at high degrees of concentration. As part of this project, a simulation model for the prediction of mixing-phase generation will be developed und experimentally validated. The simulation results will help to select experimental variables and levels.
Fig. 2: Schematic diagram of a SWM module.
Development of an asymmetric flow field flow fractionation by means of a membrane-hydrogel system for additional protein separation according the principle of gel electrophoresis and implementation of a cleaning program for long-term repeatable and reliable measurement results
Funding source: ZF4025013SB6 (in collaboration with Schambeck GmbH)
Separation of the proteins from urine and their quantification is crucial for early diagnosis of the kidney diseases. Nowadays, quantitative and qualitative marking of proteins in urine is possible in series of different measurements, thus there is still a demand for an universal measuring instrument for a comprehensive characterization of proteins in urine. Therefore, TUM and Schambeck SFD Company will develop a new system for separation of the proteins based on the asymmetric flow field flow fractionation (AF4) method using a membrane-hydrogel system. Besides the conventional separation principle of the AF4 by particle size, an electrical separation field will be applied in order to separate the molecules according to the principle of gel electrophoresis. It is very promising and efficient method, however the available AF4 systems do not always give reproducible results due to contamination of the membrane. Therefore, several different membrane-hydrogel systems will be tested in order to overcome this disadvantage and to guarantee the measurement’s reproducibility. For the best working systems, a procedure for cleaning and regeneration of membrane will be developed. In the next step, a computational simulation will be carried out in order to optimize and improve the working conditions of the separation process for prototype of AF4 flow chamber. The simulation results and model proposed will help to reproduce and predict the separation ability for different types of membrane-hydrogel systems used in AF4 flow chamber.
Fig. 3: Schematic diagram of Gel-AF4 flow chamber for separation of the proteins.
Hydroskin: Development of a novel synthetic skin equivalent of hydrogels and lipid solutions for the true-to-life imitation of age and gender specific characteristics of human skin
Funding source: ZF4025019SB7 (in collaboration with Dermatest GmbH)
To date, extraordinary efforts have been directed towards development of 3D human skin equivalents in vitro, purely from the perspective of ensuring adequate supply to mitigate the challenge of extreme shortage of such skin substitutes. This is especially during medical emergency such as burning, and skin transplants following carcinomas. Efforts have been directed towards involving live cells on 3D scaffolds made of a variety of materials, both synthetic and natural; in addition to employ purely decellularized constructs that mimic the human skin in vivo. As a consequence, several commercial 3D human skin constructs are available. In spite of these, concerns remain. The perspective has been aggravated by undesired circumstances pertaining to prohibitively high costs of these materials, problems of host rejection, inadequate morphogenesis and differentiation of the in vitro constructs, and above all, failure to successfully mimic the complex architecture of the human skin. The current project targets these lacunae. In a collaborative effort, TUM and Dermatest, GmbH will join hands in realizing the development of a lipid and hydrogel based human skin constructs specific to sex (male and female), and to a broad age group range, from neonatal to geriatric stages. The work is novel, and targets in-depth mechanical and microstructural characterizations of real human skins to establish reference points that will be crucial to develop the individual skin layers under culture conditions. The biodegradable hydrogel and lipid based artificial human skin, suited to both age and gender, will be rigorously tested for histological comparisons, with a clear focus on a probable market launch.
Nonequilibrium thermodynamic investigation of the shear banding phenomenon in entangled polyacrylamide solutions
Funding source: DFG 402813701 (in collaboration with Prof. S. Rathgeber)
When soft materials (complex fluids) are subject to strong sheardeformations, these materials can develop localized bands with different shear rates and/or concentrations, known as shear bands. It has been hypothesized that shear banding is caused in polymeric solutions by diffusion. Recently, we developed a thermodynamic polymer model taking into account Fickian diffusion and stress- induced migration. In this model, it is assumed that local gradients in concentration and stress generate a nontrivial velocity difference between the polymeric constituents and the solvent. The advantage of this model is that the differential velocity is treated as state variable. The extra boundary conditions arising from the presence of derivative diffusive terms can be directly imposed with respect to this variable. Microstructural information is therefore not anymore required but is rather an outcome of the model. The goal of this project is to verify the above-mentioned hypothesis using a combined numerical and experimental approach. The model will be systematically studied in two benchmark flows. The computations will be validated by performing a comparison with velocimetry, fluorescence snapshot, and neutron scattering experiments. The development of reliable polymer models is of importance to plastics manufacturing and other sectors like the food and pharmaceutical industries as their future application will allow to better design the textural properties of products and industrial flow processes.
In situ, real-time rheological characterization of alginate gelation
Funding source: DFG 389065834
One challenging issue in rheologyis to characterize materials undergoing fast transient structural changes during a physical process such as the gelation of polysaccharides. To investigate the kinetics of such a process, reliable real-time rheological monitoring is required. The scientific objective of this research project is to elucidate the gelation kinetics of alginate by means ofa novel rheological approach. The impact of the polysaccharide concentration, the molar ratio of calcium to carboxylate ions, the cation type, and the ionic strength will be studied in situby performing an instant infusion of divalent cations into the samples. To achieve such an infusion, the rheometer’s base, where the alginate solutions will be placed, must be modified. To provide a proof for our concept, the custom-made prototype base has been successfully tested using aqueous solutions of 1 and 1.5 wt.% alginate. The instant response of the polysaccharide to the presence of the calcium ions could be successfully recorded.In addition to the in-siturheological characterization, the microstructural changes will simultaneously be recordedusingoptical microscopy. The combined approach can provide new insights into the gelation kinetics of alginate. The findings of this study arealso of industrial relevance as this natural polysaccharide is usedin many applications in the food, cosmetic, and pharmaceutical industries.
Fluid-fluid extractor: development of a microfluidic-demonstrator for measuring the liquid-liquid equilibrium
Funding source: Bavarian Research Foundation (AZ-1285-17), in collaboration with Prof. M. Mincheva and cts GmbH
Separation and purification of fluids are the essential components of the production chain in biotechnology, food, cosmetics, chemicals and pharmaceutical industries. These processes are often very time consuming and expensive. Almost 90% of the product costs are due to the extraction procedure. Therefore, it remains to be the essential part of production optimization in those industries.
One of the frequently used techniques for this purpose is the liquid-liquid extraction. In this method, the component of interest is extracted from the original carrier by mixing it with a solvent that has a high compatibility with the target but is immiscible with the carrier. Here, the equilibrium data are of crucial importance for the optimum selection of the solvent. However, the available methods to estimate them are also very time consuming and expensive.
Fig. 4: Liquid-liquid extraction process.
This research project addresses these issues by contributing to the development of a microfluidic-demonstrator that makes the cost-effective and fast calculation of the multi-component equilibria possible. The final results of this analysis are communicated as a detailed phase-diagram via GUI of the software and can be applied for the industrial scale separation procedures.
Development of a biological degradable, sustainable, multifunctional permutation-matix as sprayable compound for refinement of convenience-products and fresh food regarding conservation, sensorical properties and taste
Funding source: ZF4025025SK7 (in collaboration with Reinert GmbH)
Because of the increasing production of meat food industry is challenged to develop sustainable preservation products therefore. Furthermore, an increasing variety regarding the offering of convenience food products arises, where the desire of the customers concerns a high sustainability of products as well as the preservation of the natural food properties regarding colour, taste and sensorical characteristics. Object of this project is the finding of a integral resolution of these partially opposing requirements and, thus, handling a very important demand. Usually, the food is covered by utilization of a dipping compound which is applied for meat and sausages as well as for cheese and for convenience food. This dipping compound is often contaminated because of the treatment condition and, furthermore, the application of the dipping compound is often very cost intensive regarding personnel. That is why the Reinert group in cooperation with the Chair of Fluid Dynamics of Complex Bio-systems of TU Munich is planning the development of a novel protection layer for food which is comprising biological degradable, lipophilic microbeads in a gelatin solution and is sprayable on food as a protection layer. By this application, the shelf-life, the sensorical properties as well as the taste of the food should be improved.
Fig. 5: Convenience products considered in this project.
Fig. 5: Convenience products considered in this project.
Compositable bioplastics cutlery as an alternative to petroleum plastics
Funding source: ZF4025033SK8 (in collaboration with Hofmann & Voss GmbH, Peiler & Klein GmbH und Loick Biowertstoffe GmbH)
The production of disposable articles made from petrochemical plastics will be banned. According to the EU Commission, one use disposable cutlery, beverage containers, food packaging and a few other consumer items made of conventional plastics are to be banned by 2030 at the latest, according to the plastics strategy of January 2018 and the packaging measures from May 2018. In some European countries, similar measures are expected earlier. For example, France will introduce a ban on non-recyclable disposable cutlery and tableware by 2020. Alternatives to these plastic items are already available, such as wooden cutler and plastics items made of PLA (polylactides). However, those alternative can not replace conventional disposable plastics as PLA is compostable only under industrial conditions and is significantly more fragile and temperature-sensitive and above all, wooden and PLA cutlery are twice to three times as expensive as conventional plastic cutlery. The aim of this project is to develop a green bio-based and biodegradable plastic that can break down into carbon dioxide, water, and biomass. The developed material will be made from renewable materials such as flax mucilage, Zein protein. Bioplastics from renewable resources represent a new generation of plastics that reduces the impact on the environment, both in terms of energy consumption and the amount of greenhouse gas emissions.
Fig. 6: Secondary agricultural product for cutlery production.
Development and characterization of a novel bio-based and bio-degradable polymer to create “green” buildings blocks
Funding source: ZF4025039SB9 (in collaboration with Juchheim Laborgeräte GmbH, Oberpfälzer Kunststofftechnik GmbH, Richter & Stegner Steuerungstechnik GmbH, kama Maschinenbau GmbH)
Sustainability and the idea of new environmentally friendly products is a topic of high interest in society nowadays. It is important to find alternatives to the commercially petroleum-based plastics sold in retail trade as toys, plastic bags, microwave compatible products etc. Today there is already some progress in the field of polymer research to manufacture products that are more compatible with the environment but still either not bio-based or bio-degradable at the same time. The aim of this project is to develop a novel bio-based polymer that is simultaneously totally bio-degradable in nature to avoid any new formation of microplastic particles. The polymer should consist of cellulose as a base and further modified with gelatine and zein protein. We want to offer a “green” alternative to the normal non-degradable plastics that are made of fossil resources to be used in the field of toy industry.
Fig. 7: Plastics; today's material used in the toy industry.
Development of smart mite insecticide capsules using the single emulsion solvent evaporation method
Funding source: ZF4025045A19 (in collaboration with Alpha-Biocare GmbH)
The house dust mites usually infest mattresses, pillows, and carpets and are considered a primary source of allergens and one of the fundamental triggers of mainly allergic respiratory diseases. They also cause sleep disorders and tiredness, which negatively affects work performance and imposes considerable economic consequences. This impact is even more tangible in Europe because of suitable climate conditions for mite growth. According to the annual Asthma survey, 64% of asthma in the UK, and around 5 million asthma cases in Germany was due to dust mites. Correspondingly, the increasingly global market demands led to the production of different kinds of commercial miticides such as mite sprays, biocides, and mite protection cover. Current products are usually limited to contact avoidance or use toxins that often only inhibit mite growth. The aim of the project is the development of a highly effective, long-term mite control agent. This project investigates new environmentally friendly alternatives by encapsulating the new natural acaricides into suitable and biodegradable microparticles using the solvent-emulsion evaporation method. Another advantage is the reduced amount required for the application as the release will be triggered mechanically.
Fig. 8: New environmentally friendly insecticide cycle.