Interfacial properties of green leaf cellulosic particles

Abstract

Cellulosic pulp from sugar beet leaves was fractionated and assessed on its interfacial properties. After pressing leaves to express the juice, the press cake was washed at alkaline pH (pH 9) to remove residual protein, dried, milled and air classified. The obtained cellulosic particles mainly consisted of insoluble dietary fibre (77.8% w/w) with remaining proteins (6.3% w/w) and exhibited considerable interfacial activity. The protein impurities contribute to the surface charge of the particles and provide surface activity, leading to spontaneous diffusion of the particles during the interfacial tension analysis; whereas the particle adsorption kinetics were characteristic of soft particles or Pickering emulsifiers. The interfacial rheology measurements showed abnormal behaviour and unusual drop shape upon deformation, hindering interpretation of the analysis but still suggesting a rigid interface with strong physical particle-particle interactions. Stable oil-in-water emulsions were produced using cellulosic particles, and despite phase separation, the emulsions were stable against coalescence. The results suggested that mostly fine particles (0.04–1.0 μm) were responsible for the interfacial stabilisation, given the small oil droplets obtained (2–5 μm); whereas larger particles (>10 μm) created a network in the continuous phase, which was responsible for the emulsion phase separation. It was concluded that the cellulosic particles had a soft nature and suitable shape to produce stable Pickering emulsions, which can be used as food-grade particles for food and pharma applications.