Emulsifying and stabilizing properties of functionalized orange pulp fibers

The present work describes the emulsifying properties of dried orange pulp fibers. Their surface activity is believed to originate from the proteins (∼8%) and pectins (∼35%), while the cellulose (>45%) enables the fibers to act as thickener. The surface activity of the dried fibers was compared to the one of their pre-activated counterparts. High pressure homogenization at 700 bar prior drying was used for this, which allowed obtaining significantly finer emulsions. Rheology of the emulsions demonstrated that at same fiber:water ratio, a critical concentration (c*) of 3.1 wt% was found when using pre-activated fibers. This corresponded well with the c* of suspensions without oil. The non-activated fiber emulsions had a much higher c*. Interestingly, no coalescence could be observed at room temperature during 2 weeks when G′ reached 345 Pa. CLSM imaging demonstrated increased amounts of proteins at the oil-water interface in activated fiber emulsions, which explained their higher surface activity.