Synthesis of Lignin Nanoparticles and Their Application in the Stabilization of Water-in-Water Pickering Emulsions: A New Technology for Valorization of Lignin from Sugarcane Bagasse

Water-in-water (w/w) emulsions can mimic biological environments, and their stability is ensured by adding nanoparticles capable of adsorbing at liquid-liquid interfaces. To enhance the properties of w/w emulsions, there is a search for new sources of nanoparticles that are attractive for the food and biomedical fields. Thus, the present study investigated the use of sugarcane bagasse lignin (a cheap, nontoxic, and biodegradable polymer) as a source of nanoparticles for Pickering emulsions with maltodextrin (MD) and polyethylene glycol 6000 (PEG 6000). The nanoparticles were prepared from alkaline lignin (ALNP) and oxidized alkaline lignin (OLNP), and their application was performed using different dosages in the w/w systems (0%, 0.1%, 0.3%, 0.5%, and 1%, wt/wt). The nanoparticles presented different sizes, with OLNPs (327.8 nm) being smaller than ALNPs (689.8 nm). The systems with OLNPs showed better emulsification indices and smaller droplet sizes than systems with ALNPs. The concentration of nanoparticles and the volume of the dispersed phase influence the stability of the studied emulsion. The most promising stabilization results were obtained at a concentration of 1% wt/wt of OLNPs with an emulsification index of up to 63%. These results, combined with the extensive availability of functional groups in lignin, make this polymer a potential candidate for advanced studies of w/w emulsions.