Emulsion stability and microfluidics

1. Emulsion stability and microfluidics PhD. Student: K. Muijlwijk, MSc Phone: +31 317 482240 Thesis advisor: Prof. C.G.P.H. Schroën E-mail: kelly.muijlwijk@wur.nl Supervisor: C.C Berton-Carabin URL: www.fpe.wur.nl/UK Research group: Food Process Engineering Research school: VLAG Supported by: NanoNextNL Period: February 2013 – February 2017 • Introduction • Microfluidics can be used to produce emulsions but also to study the stability of emulsion droplets during production and further processing. Earlier work in our group has provided us with various methods to study mainly production of simple emulsions but until now they have not yet been used for more complex food systems. In this project we will investigate the possibility to use microfluidics as a tool to study the stability of food-grade emulsions during production, processing and storage. Figure 2. Snapshots of the collision chamber with oil-in-water emulsion droplets stabilised with 10-3 and 10-8 M SDS.3 Approach Previous research has shown that small droplets with a narrow size distribution can be obtained in Y-junctions (Figure 1).1 So far, only simple surfactants have been used in these micro-channels to produce oil-in-water emulsions. The use of more complex surfactants like proteins are of interest for food applications, since proteins are known to be very efficient stabilisers of interfaces. Y-junctions will be used to produce protein-stabilised emulsion droplets, and also investigate dynamic interfacial tension effects during droplet formation [2]. The effect of processing conditions on the (dynamic) interfacial tension can be determined, and this is necessary information to predict the droplet size. Figure 3. Series of images during a compression experiment with the micro-centrifuge, the last image is the digitalised version used for image analysis.5 Project aim In this project we focus on the production of small protein-stabilised emulsion droplets with microfluidic Y-junctions. Influence of processing parameters on adsorption of proteins to the emulsion interface will be investigated. Next to that, the stability of food-grade emulsions during production and storage will be tested with the micro-channel, collision chamber and micro-centrifuge. Figure 1. Emulsion droplet production at a microfluidic Y-junction.1 Besides droplet formation, also coalescence of droplets (stability) will be investigated. Several methods will be used to mimic the conditions during processing and storage. Stability during processing can be studied in situ with a micro-channel in which droplet contacts can be monitored with a high-speed camera attached to a microscope (Figure 2).3,4 This allows us to follow the collision and possible coalescence of droplet pairs for which the film drainage profile and coalescence time can be calculated. Alongside, a micro-centrifuge can be used for accelerated storage tests of emulsions.5A chip with a dead-end chamber is placed in a micro-centrifuge with an attached microscope and camera. In this set-up, triggered pictures can be made of the emulsion during centrifugation (Figure 3), and in the current project, food related emulsions will be studied. Acknowledgement This work is supported by NanoNextNL, a micro and nanotechnology consortium of the Government of the Netherlands and 130 partners. References 1. M.L.J. Steegmans, K.G.P.H. Schroën, and R.M. Boom, Langmuir, 2009, 25, 3396-3401. 2. M.L.J. Steegmans, A. Warmerdam, K.G.P.H. Schroen, and R.M. Boom, Langmuir, 2009, 25, 9751-9758. 3.. T. Krebs, K. Schroën, and R. Boom, Soft Matter, 2012, 8, 10650-10657. 4. T. Krebs, K. Schroen, and R. Boom, Lab Chip MiniaturisationChem. Biol., 2012, 12, 1060-1070. 5. T. Krebs, D. Ershov, C.G.P.H. Schroen, and R.M. Boom, Soft Matter, 2013, 9, 4026-4035.