Continuous encapsulation via membrane emulsification and complex coacervation
Creators: name: Barton, Alix
Publisher: name: Loughborough University
Year: 2020
Subjects: subject: 99999 Engineering not elsewhere classified
subject: FOS: Other engineering and technologies

description: Complex Coacervation (CC) is one of the techniques that can be used in industries such as food and pharmaceutical, to encapsulate and protect important compounds or to isolate volatile ones. This research is investigating a novel way of encapsulating emulsions via combining CC with the emulsion producing technique Membrane Emulsification (ME). This combination for encapsulation will then be scaled up and converted to continuous production. Batch scale ME were completed using the Dispersion Cell (DC). Initial experiments were completed using oil in water single emulsions moving on to using water in oil in water double emulsions and eventually progressed to a dispersed phase entrapping 10% (w/w) and 30% (w/w) Ascorbic Acid (AA) solution in the primary water phase. The experiments investigated how emulsion droplet size and CC shell thickness were affected by various parameters. These included: varying the transmembrane flux and the shear on the membrane surface, Total Biopolymer Concentration, pH change, amount of dispersant injected and cooling time. The combination of parameters that produced the thickest CC shell and the most uniform capsules produced by ME in this study were found. Encapsulation efficiency 93% and 96% for the 10% (w/w) and 30% (w/w) AA solutions respectively was also assessed via monitoring AA release over time and verified by titration. Experimentation for the scale up of ME was completed using Azimuthal Oscillating System (AOS). Comparing both DC and AOS, DC flux is a lot higher than the AOS, 147000 L m2 h-1 compared with 793 L m2 h-1 respectively. However, both methods produced droplets of size within the error bars of each other for the same shear stress. For continuous production, ME by AOS was replaced with a Continuous Dispersion Cell (CDC) and integrated with an Oscillatory Flow Reactor (OFR) for continuous CC. CC requires slow cooling of the emulsion to room temperature (≤1ºC min-1) as both shell thickness and encapsulation efficiency are influenced by cooling rate. Residence Time Distribution experiments were performed using in lab made capsules containing the fluorescent 1,3-diphenylisobenzofuran. Optimal conditions were the ones closest to plug flow that also resulted in capsule suspension in the OFR. Close to plug flow conditions were desirable to ensure homogenous conditions regarding temperature for the droplets. The cooling profile inside the OFR was investigated at different flow rates and cooling liquid temperatures. This was done using in-lab made thermotropic Liquid Crystal (LC) capsules of size 80µm with colour change range between 25 and 37ºC. The optimal cooling profile, in the OFR, was found and was then validated by continuous microencapsulation of sunflower oil. Capsule shells were cross-linked by glutaraldehyde to increase their stability and freeze dried. Finally, the Strength of the produced shell was explored using 30% (w/w) AA capsules and a novel method using a different variation of bulk capsule testing. The method has shown potential to be effective, but more research is needed to enhance the technique further.