Stabilization of oil continuous emulsions with colloidal particles from water-insoluble plant proteins

Emulsions stabilized by surface active particles are becoming an attractive alternative to conventional surfactant-stabilized emulsions. Biobased, environmentally friendly, and edible particles are particularly interesting for applications in foods, agriculture, and consumer products. Previously, water insoluble proteins such as prolamins have been only used as a platform for stabilization of water continuous emulsions. In this paper, we investigate the ability of zein particles to stabilize oil continuous emulsions. We synthesized and used zein particles in the form of (i) an aqueous, or (ii) an oil suspension. Aqueous suspensions of zein particles resulted in water-in-oil (w/o) emulsions that were generally stable for more than an hour, with up to 30 vol% water as the dispersed phase. Cryo-SEM images show that only a small fraction of zein particles are adsorbed at the oil-water interface as Pickering stabilizers. Adding an oil soluble surfactant (lecithin) prior to emulsification with zein particles in an aqueous suspension promoted the formation of oil-continuous emulsion with phase inversion point at 40 vol% of water. Zein particles suspended in oil produced less stable emulsions, which showed reversible phase inversion attributed to the electrostatic repulsion of hydrophilic protein loops above their isoelectric point. Our results show that zein particles act as a predominantly hydrophilic stabilizer that requires control prior to emulsification to form w/o emulsions. These emulsions, however, have only a limited stability

Fabrication of Environmentally Biodegradable Lignin Nanoparticles

We developed a method for the fabrication of novel biodegradable nanoparticles (NPs) from lignin which are apparently non-toxic for microalgae and yeast. We compare two alternative methods for the synthesis of lignin NPs which result in particles of very different stability upon change of pH. The first method is based on precipitation of low-sulfonated lignin from an ethylene glycol solution by using diluted acidic aqueous solutions, which yields lignin NPs that are stable over a wide range of pH. The second approach is based on the acidic precipitation of lignin from a high-pH aqueous solution which produces NPs stable only at low pH. Our study reveals that lignin NPs from the ethylene glycol-based precipitation contain densely packed lignin domains which explain the stability of the NPs even at high pH. We characterised the properties of the produced lignin NPs and determined their loading capacities with hydrophilic actives. The results suggest that these NPs are highly porous and consist of smaller lignin domains. Tests with microalgae like Chlamydomonas reinhardtii and yeast incubated in lignin NP dispersions indicated that these NPs lack measurable effect on the viability of these microorganisms. Such biodegradable and environmentally compatible NPs can find applications as drug delivery vehicles, stabilisers of cosmetic and pharmaceutical formulations, or in other areas where they may replace more expensive and potentially toxic nanomaterials

Preparation of Reinforced Anisometric Patchy Supraparticles for Self Propulsion

The preparation of fumed silica based anisometric supraparticles with well defined catalytically active patches suitable for self propulsion is presented here. These sub millimeter sized particles can self propel as they contain Pt covered magnetite Fe3O4 nanoparticles, where the Pt can decompose catalytically a fuel like H2O2 and thereby propel the supraparticles. By their magnetic properties, the catalytically active nanoparticles can be concentrated in patches on the supraparticle surface. The goal is to obtain robust supraparticles with well defined patchiness and long time stability during self propulsion through evaporation induced self assembly EISA on a superhydrophobic surface. The latter is a major issue as oxygen evolution can lead to the disintegration of the supraparticles. Therefore, enhanced mechanical stability is sought using a number of different additives, where the best results are obtained by incorporating polystyrene microspheres followed by heat treatment or reinforcement with microfibrillated cellulose MFC and sodium trisilicate Na2SiO3 . The detailed internal structure of the different types of particles is investigated by confocal micro X ray fluorescence spectroscopy CMXRF , which allows for precisely locating the catalytic Fe3O4 Pt nanoparticles within the supraparticles with a resolution in the m range. The insights on the supraparticle structure, together with their long time stability, allow fabricating optimized patchy supraparticles for potential applications in propulsion enhanced catalysi