Drying of Pickering emulsions in a viscoelastic network of cellulose microfibrils

Oil-in-water Pickering emulsions at high volume fractions (50 wt % oil) are prepared using cellulose microfibrils (CMF) from plant cell wall materials as emulsifiers and stabilizer. Confocal microscopy is used to monitor the changing CMF network over time and the rate of oil droplet coalescence. Without addition of glycerol the drying emulsion quickly coalesces, and a significant oil separation ensues. The rate of coalescence and the percentage of coalescence droplets and oil separation decrease as the concentration of CMF is increased. Addition of glycerol into the emulsions decreases the extent of droplet coalescence and oil separation. At 10 wt% added glycerol, coalescence could not be prevented but oil separation is minimal: the oil is mainly contained into honeycomb shaped cells made of CMF and glycerol. The results demonstrate the influence of the aqueous phase on the coalescence and film forming properties of CMF stabilized Pickering emulsions.