Biopolymer-based structuring of liquid oil into soft solids and oleogels using water-continuous emulsions as templates.

Physical trapping of a hydrophobic liquid oil in a matrix of water-soluble biopolymers was achieved using a facile two-step process by first formulating a surfactant-free oil-in-water emulsion stabilized by biopolymers (a protein and a polysaccharide) followed by complete removal of the water phase (by either high- or low-temperature drying of the emulsion) resulting in structured solid systems containing a high concentration of liquid oil (above 97 wt %). The microstructure of these systems was revealed by confocal and cryo-scanning electron microscopy, and the effect of biopolymer concentrations on the consistency of emulsions as well as the dried product was evaluated using a combination of small-amplitude oscillatory shear rheometry and large deformation fracture studies. The oleogel prepared by shearing the dried product showed a high gel strength as well as a certain degree of thixotropic recovery even at high temperatures. Moreover, the reversibility of the process was demonstrated by shearing the dried product in the presence of water to obtain reconstituted emulsions with rheological properties comparable to those of the fresh emulsion.

Edible applications of shellac oleogels: spreads, chocolate paste and cakes.

We demonstrate three potential edible applications of shellac oleogels as (i) a continuous oil phase for preparation of emulsifier-free, structured w/o emulsions (spreads), (ii) a replacer for oil-binders in chocolate paste formulations and (iii) a shortening alternative for cake preparation. Water-in-oil emulsions with up to 60 wt% water were prepared without the need for an emulsifier by simply using shellac oleogels as the continuous oil phase. The water droplets in these emulsions (size < 40 µm) were stabilized via interfacial and bulk crystallization of shellac. Chocolate paste prepared by complete replacement of an oil-binder and a partial replacement of palm oil (∼27%) with a shellac oleogel, showed no sign of 'oiling-out' when stored at elevated temperature (30 °C) for several weeks. Further, cakes prepared using oleogel-based w/o emulsions (20 wt% water) as a shortening alternative showed comparable functionalities (texture and sensory attributes) to the standard cake.