In this work, the tribological behaviour of o/w model emulsions stabilized by native corn starch particles in association with a surface-active olive leaf phenolic extract (OLE) was studied. Preliminarily, starch particles were submitted to a high-pressure homogenization pre-treatment and were then separated, by sedimentation, into small (<5 μm, centered on 2.5 μm) and large (<50 μm, centered on 17 μm) particles. Oil-in-water emulsions (10 % dispersed phase, w/v) were prepared using native corn starch particles in the presence of OLE as an emulsifier and characterized for particle size, microstructure and tribological behaviour. OLE and starch particles were both needed for system structuration, providing stability with different mechanisms. OLE triggered oil droplet formation acting as a low molecular weight emulsifier, while starch particles played a different role in the stabilization of the emulsions based on their size: the small starch particles provide stability by adsorbing onto the o/w interface, while the large particles provide stability by forming an interconnected network in the continuous phase, which embedded OLE-stabilized oil droplets. The tribological study showed that emulsions stabilized by small particles showed higher friction coefficients. In these emulsions, the stable emulsion droplets provided particle lubrication. In emulsions stabilized by large particles, lower friction coefficients were observed, which was due to the low stability of the oil droplets. The oil droplets could easily coalesce under flow, causing the formation of an oil film, which was more efficient in lowering the friction coefficient than the oil droplets stabilized with smaller particles. Such findings demonstrated that the size of starch particles played an important role in the stabilization mechanism of the emulsions as well as of their lubrication properties, and can be used to control different properties of emulsions.
Stability and tribological properties of oil-in-water emulsions stabilized with native corn starch and olive leaves phenolic extracts
Farooq U;Di Mattia C.
;Faieta M.;Pittia P.
2025-01-01
Abstract
In this work, the tribological behaviour of o/w model emulsions stabilized by native corn starch particles in association with a surface-active olive leaf phenolic extract (OLE) was studied. Preliminarily, starch particles were submitted to a high-pressure homogenization pre-treatment and were then separated, by sedimentation, into small (<5 μm, centered on 2.5 μm) and large (<50 μm, centered on 17 μm) particles. Oil-in-water emulsions (10 % dispersed phase, w/v) were prepared using native corn starch particles in the presence of OLE as an emulsifier and characterized for particle size, microstructure and tribological behaviour. OLE and starch particles were both needed for system structuration, providing stability with different mechanisms. OLE triggered oil droplet formation acting as a low molecular weight emulsifier, while starch particles played a different role in the stabilization of the emulsions based on their size: the small starch particles provide stability by adsorbing onto the o/w interface, while the large particles provide stability by forming an interconnected network in the continuous phase, which embedded OLE-stabilized oil droplets. The tribological study showed that emulsions stabilized by small particles showed higher friction coefficients. In these emulsions, the stable emulsion droplets provided particle lubrication. In emulsions stabilized by large particles, lower friction coefficients were observed, which was due to the low stability of the oil droplets. The oil droplets could easily coalesce under flow, causing the formation of an oil film, which was more efficient in lowering the friction coefficient than the oil droplets stabilized with smaller particles. Such findings demonstrated that the size of starch particles played an important role in the stabilization mechanism of the emulsions as well as of their lubrication properties, and can be used to control different properties of emulsions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
