Prestigious national and international experts presented their latest findings on particle characterization and particle size distribution, dispersion parameter determination, stability testing, shelf-life prediction and adhesion testing, covering very different applications from the industry and academia – all of them measured with LUM devices [1].

Stability evaluation and shelf-life prediction was clearly the focus topic of most of the speakers at 2019’s conference – 13 out of 22 contributions presented this subject.
In the evening of the first conference day, LUM invited the guests to an exclusive guided tour through the Tierpark, Europe’s largest animal park, followed by an abundant gala dinner in the Tierpark Restaurant Patagona.

The opening plenary lecture of the conference was one of the fillet pieces among all of the contributions. Wolfgang Peukert, Chair of the Institute of Particle Technology (LFG) of the Friedrich-Alexander-University Erlangen-Nuremberg and Spokesperson of the Interdisciplinary Centre for Functional Particle Systems (FPS) as well as of CRC 1411, Design of Particulate Products, lectured on “Progress in particle characterization by sedimentation analysis”.  His profound overview on recent theoretical and experimental achievements of analytical centrifugation and future developments in progress laid a prefect foundation for the coming conference talks and discussion [2].

Stability Testing and Shelf-Life Prediction
Another highlight of the conference was the second day’s lecture of Supratim Ghosh, professor at the University of Saskatchewan in Canada. Professor Ghosh presented recent advancements in food science. Using a LUMiSizer® his team is engaged with 1) the enhanced creaming stability of lentil protein-stabilized nanoemulsion gels compared to liquid nanoemulsions, 2) the storage stability of lentil protein-stabilized nanoemulsions containing excess proteins, 3) the stability of emulsions made with lentil protein-fenugreek gum complexes and 4) the improved stability of coarse oil-in-water (O/W) emulsions by the synergetic actions of two lipophilic emulsifiers.

Firstly, his research results showed a nearly unlimited storage stability of lentil protein-stabilized nanoemulsion gels in comparison to conventional liquid nanoemulsions. Secondly, Ghosh analyzed aging of lentil protein-stabilized nanoemulsions containing excess proteins by change in droplet size distribution and instability index. Optimum stability resulted for nanoemulsions containing 2% of lentil protein isolate, which was in line with prediction by instability index obtained by accelerated creaming but was not detected by Zeta potential. In addition, LUMiSizer was used to optimize processing conditions to enhance lentil protein emulsifier properties. Further, his experiments proved a significantly lower creaming velocity of lentil protein isolate-fenugreek gum (LPI-FG)-complex emulsions compared to emulsions stabilized with individual polymers like lentil protein isolate, fenugreek or gum Arabicum. Thus, LPI-FG complexes are a more efficient stabilizer for beverage emulsions. Last but not least, Ghosh proved that the combined use of the emulsifiers monoglyceride and polyglycerol polyricinoleate displayed a considerably higher stability compared to emulsions compounded with each of the emulsifiers individually. He concluded that application of LUMiSizer in food colloid research provided a novel and effective means of understanding and predicting their stability that would not have been possible otherwise [3].

Steven P. Armes from the Department of Chemistry at the University of Sheffield introduced Pickering nanoemulsions sterically stabilized by block copolymer nanoparticles. Ostwald ripening is a critical destabilization process for nanoemulsions in general. Aqueous solubility of oil dictates long term stability. LUMiSizer is much more reliable than DLS for assessing long term Pickering nanoemulsion stability [4].

Several representatives of renowned companies from the food, cosmetics and consumer goods industries also presented their latest findings.

Anna Kuzmicheva from PepsiCo Company in Moscow described how she used the LUMiFuge to assess the individual stability out of a range of different milk-juice and dairy product recipes, thus determining the ideal amount of pulp and whole cells respectively choosing the most appropriate skimmed milk powder as raw material with regard to sedimentation velocity. Another interesting aspect of her talk was the use of LUMiFuge as an easy means to detect adulteration in milk products. Hence, Kuzmicheva considered analytical centrifugation as a convenient tool for R&D – especially for shelf-life prediction- and quality control purposes in the food industry.

Especially in the cosmetics and consumer goods industry, time to market is an important success factor, when it comes to developing and accessing new product formulations. Accordingly, Andrea Kargerová from the Brno University of Technology [5], Richard Lehmann from BCL Dr. Lehmann GmbH & Co. KG [6] and Stanislav Jaracz from Colgate Palmolive unanimously concluded that LUMiFuge® and LUMiSizer are effective and time-saving tools for determining product stability and predicting the shelf-life of improved or new product formulations.

HP Inc. from San Diego also took advantage of the accelerated stability testing with the LUMiSizer. Representative Yubai Bi explained in his presentation how he was able to predict the stability of wax-containing inkjets. For this purpose, he determined the scattering and absorbing power of wax and colorants as well as the pigment settling rate and wax creaming rate of the ink formulations.

Process optimization
Holger Rautschek from Wacker Chemie AG reported on various applications as diverse as protection of buildings against weathering, process optimization of a silicon emulsion for the cosmetic industry, stability of an antifoam as well as on emulsifier selection and optimization of production processes. Exemplarily he showed that determination of the instability index with the LUMiFuge was a better indicator of storage stability than particle size [7].

KRONOS International representative Sven Böhm explained how he combined a lab centrifuge and a LUMiReader® X-Ray in order to evaluate the sedimentation and re-dispersing properties of highly filled Titanium Dioxide dispersions [8].

In addition to speakers directly from the industry, participants from academia and research organizations presented their research results on process development. Merouane Khammar from Natural Resources Canada introduced the audience into the processes of bitumen recovery from tar sands. He focused on filtering centrifuges for the separation of mineral particles from solvent diluted bitumen. Khammar used custom-made filtration cells for laboratory experiments of solvent extraction in a LUMiFuge to obtain unsaturated flow properties for large scale applications in continuous filtering centrifuges [9].

Alex van Silfhout from the Utrecht of University and his team aimed to find the utmost stable ferrofluid suitable for the magnetic density separation of plastic waste from water. This technology has a high potential for the recycling industry as it takes advantage of the fact that solid particles dispersed in ferrofluid levitate if they are exposed to an external magnetic field. A key requirement for this application is the stability of the ferrofluid colloidal dispersions in the magnetic field applied. To this end, he measured the sedimentation rate of magnetic nanoparticles before and after exposed to magnetic field with the LUMiReader X-Ray [10].

Klaus-Hendrik Mittenzwey from Optosphere Spectoscopy GbR, Berlin explained an easy and convenient method of determining fat, protein and dry matter in milk with the newly developed LUMiFlector by means of Multi-Reflectance-Spectroscopy (MRS – Technology) [11].

Presentations of academia presented also new applications and approaches by LUM instruments to characterize dispersed particles and dispersion products.  Timothy N. Hunter from the Chemical & Nuclear Engineering School as part of the University of Leeds gave a talk on “Incorporation of centrifugal and DLVO forces into simulations of dispersion sedimentation and validation with LUMiSizer data” [12].

Thanks to Albert P. Philipse from the University of Utrecht and his team, the participants learned how analytical ultra-centrifugation allows the simultaneous determination of colloid or protein charge and mass.

Shin-ichi Takeda from Takeda Colloid Techno-Consulting Co. Ltd. proved that sedimentation techniques compared to Dynamic Light Scattering and laser diffraction methods are a time-saving and convenient way to determine Hansen Solubility (Dispersibility) Parameters of dispersions.

Adhesion testing
In the field of materials and adhesion testing Uwe Beck from the German Federal Institute for Materials Research and Testing (BAM) contributed with a presentation about tensile and compressive testing with an analytical centrifuge. According to Beck, devices like the multi-sample LUMiFrac® make it possible to determine in an efficient way, e.g., the assembly, bonding or adhesive strength for multiple samples compared to traditional single-sample testing methods. In addition, no clamping is required anymore. With the help of the guiding sleeve tangential forces can be avoided and, furthermore, neither Euler nor Coriolis forces affect the testing results. Finally, Beck claimed the efficiency of the new centrifugal material testing hence it works according to EN 15870, ENISO 4624, EN ISO 6506/6507, VDI/VDE 2616 and DIN EN ISO/IEC 17025 which makes it a perfect tool for research and development as well as for quality control matters [13].

Mark Zimmermann and his team from the Fraunhofer Institute for Applied Polymer Research IAP work on a basic system for the production of multivalent anisotropic colloids by creating patchy silica particles with the help of microcontact printing with polymeric inks. With the LUMiFrac they successfully developed a printing apparatus using microcontact printing materials, springs and centrifugation [14].

Young Scientist Award
Since 2014 LUM traditionally honors a promising young scientist who has gained outstanding research results in the fields of particle- and dispersion analysis or material testing. In 2019 three candidates were shortlisted, all of them used a LUMiSizer for their studies. Two of them, Chi Diem Doan and Kunal Kadiya, both mentees of Supratim Ghosh, came from the University of Saskatchewan in Canada.

Chi Diem Doan investigated the feasibility of using pea protein nanoparticles (PPN) for manufacturing so-called Pickering emulsions. These emulsions are a worthwhile application with numerous possibilities for use in the food, cosmetics and pharmaceutical industries. For this purpose, she compared the stability of PPN-emulsions and soluble molecular pea protein-stabilized emulsions (PPS) at different pH-levels. Creaming stability measurements with LUMiSizer proved an outstanding stability of PPN-emulsions compared to PPS-emulsions, even over several months [15].

The second candidate from Canada, Kunal Kadiya, examined the influence of the emulsifier concentration and inter-droplet interactions on the oil droplet-effective volume fraction as well as the rheological behavior of concentrated nanoemulsions. His studies aimed to provide important insights for the R&D-departments of various industrial manufacturers of such emulsions. On this occasion, Kadiya investigated the stability of DLVO and non-DLVO colloids in regard to gelation and creaming stability. Using both, the anionic emulsifier sodium dodecyl sulphate and the food-gradient anionic emulsifier Citrem (Citric acid esters of mono- and diglycerides), he tested and compared the stability of the nanoemulsions and predicted the gelation using accelerated gravitational separation. He came to the conclusion that the inter-droplet-forces and the rheology of nanoemulsions can be manipulated by removing excess emulsifier from the continuous phase. This procedure helps to increase the stability against gravitational separation and the shelf-life significantly. For a more basic understanding he evaluated the inter-droplet interactions using a set of compressional – dilatational cycles. This allowed to predict the mechanism of gelation of nanoemulsions [16].

The third nominated candidate was Richard-Sebastian Moeller from the Karlsruhe Institute of Technology, Germany. He presented a rather particular topic from the baker’s trade which was part of his dissertation. In his lecture “From the Life of Proving Cloths” Richard-Sebastian described how he found a method to help bakers extending the service period of so-called proving cloths. He described that bakers often have troubles removing the dough balls without leaving any residues on the cloth after placing the dough balls on the proving cloth for rising – which is also a matter of hygiene. Moeller analyzed the dough adhesion with a self-constructed cell. Testing several methods, he found out that brushing the proving cloth in between increases the hairiness of the material – thus the adhesion of dough is reduced considerably. With his research results he helped the baker’s trade to extend the service period of proving cloths significantly between the washes with a simple additional process step [17].

It was a very close decision but due to the great contribution of his work for the whole bakers’ guild, especially in the light of sustainability and resource saving, LUM awarded Richard-Sebastian Moeller with the Young Scientist Award 2019 including a trophy money of 1,000 Euro.

The next LUM Young Scientist Award will be awarded at the 10th International Conference for Dispersion Analysis and Materials Testing – taking place in Berlin from January 25-26, 2021.

The Call for Papers and Registration for 2021 are available on https://conference2021.lum-gmbh.com/.

References:
[1] Abstracts of the 9th International Conference on Dispersion Analysis & Materials Testing in Berlin, Germany, 22-23 May, 2019, https://www.dispersion-letters.com/ available online on 25.5.2020 09:46
[2] D. Lerche, L. Rodriguez, T. Sobisch, S. Süß, D. Segets, W. Peukert: Profiling particle surface by Hansen Parameters to predict particle-particle and particle-liquid interaction; XVIth International Conference on Surface Forces, 2018, Book of Abstracts, Abstract O10, P.36
[3] M. Primozic, A. Duchek, M. Nickerson, S. Ghosh: Formation, stability and in vitro digestibility of nanoemulsions stabilized by high-pressure homogenized lentil proteins isolate; Food Hydrocolloids, 77, 2018, 126-141
[4] K. L. Thompson, M. J. Derry, F. L. Hatton, S. P. Armes: Long-Term Stability of n‑Alkane-in-Water Pickering Nanoemulsions: Effect of Aqueous Solubility of Droplet Phase on Ostwald Ripening; Langmuir, 34, 2018, 9289−9297
[5] J. Smilek, M. Lastuvkova, K. Vlachova, L. Oharek, A. Kargerova, O. Machacek and J. Roupec: Sedimentation analysis of magnetorheological fluids stabilized by amphiphilic compounds studied by analytical centrifuge; 32nd Conference of The European Colloid and Interface Society, 2018, Book of Abstracts PP3.10, P. 225
[6] Bio-Chemisches Laboratorium Dr. Lehmann GmbH & Co. KG: Survey of Galenic Stability of Dispersed Systems via the Optical Centrifuge; Version: 1.1, available online on 11.02.2015
[7] H. Rautschek, S. Kröner, R. Schröck, C. Spörk: Process for continuous production of stable silicone emulsions; Patent Application, 2017, WO2017046017 A1
[8]  T. Sobisch, D. Lerche, T. Koch: Delayed sedimentation induced by osmotic effect in polymer free aqueous suspensions, https://www.researchgate.net/publication/337195353_Delayed_sedimentation_induced_by_osmotic_effect_in_polymer_free_aqueous_suspensions, available online on 25.5.2020 9:21
[9] M. Khammar, Y. Zhu, Y. Xu: Centrifugal recovery of solvent-diluted bitumen from oil sands; Minerals Engineering, 136, 2019, 8-17
[10] A. v. Silfhout, B. Erné: Magnetic detection of nanoparticle sedimentation in magnetized ferrofluids; Journal of Magnetism and Magnetic Materials, 472, 2019, 53-58
[11] P. Dumeier, K.-H. Mittenzwey, G. Sinn, D. Lerche: Off- and In-line monitoring of processed milk by MRS-Technology, Filtech 2019, Köln, Germany, 22-24 October 2019, https://filtech.de/conference/conference-review/abstract-information?abstract_id=822 available online on 25.5.2020, 09:24
[12] E. Antonopoulou, C. F. Rohmann-Shaw, T. C. Sykes, O. J. Cayre, T. N. Hunter, P. K. Jimack: Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force; Physics of Fluids 30, 030702 (2018); https://doi.org/10.1063/1.5010735
[13] S. Hielscher, U. Beck, T. Lange, D. Grunwald, J. M. Stockmann, D. Lerche, U. Rietz: Die Zentrifuge als universelles Prüfsystem für Beanspruchungen auf Zug und Druck; Beitrag zu einem Tagungsband 13. ThGOT Thementage Grenz- und Oberflächentechnik und 11. Thüringer Biomaterial-Kolloquium, INNOVENT e.V., 2018, Germany
[14] M. Zimmermann: Multifunctional Patchy Silica Particles via Microcontact Printing; Univ.-Diss. zur Erlangung des akademischen Grades "doctor rerum naturalium", Mathematisch-Naturwissenschaftliche Fakultät, Institut für Polymermaterialien und Polymertechnologien der Universität Potsdam, Germany, 2019
[15] C. D. Doan, S. Ghosh: Formation and Stability of Pea Proteins Nanoparticles Using Ethanol-Induced Desolvation; Nanomaterials 2019, 9(7), 949
[16] K. Kadiya, S. Ghosh: Conversion of viscous oil-in-water nanoemulsions into viscoelastic gels upon removal of excess ionic emulsifier; Langmuir 2019, 35, 52, 17061-17074
[17] R.-S. Moeller: Adhesion and cleanability of surfaces in the baker’s trade; Journal of Food Engineering, Volume 194, February 2017, 99-108