Síntese de nanopartículas de lignina do bagaço da cana-de açúcar para aplicação na estabilização de emulsões pickering água/água e encapsulamento de bioativos

Abstract

Lignin, despite being the second most abundant biopolymer on the planet, remains underutilized in the production of value-added products. In response to this, studies have been exploring lignin's applications in various fields, with the production of nanoparticles emerging as a promising avenue for lignin valorization. Lignin nanoparticles have already been tested for their ability to stabilize oil/water (O/W) or water/oil (W/O) Pickering emulsions, including the encapsulation of bioactives such as quercetin, a bioflavonoid with antioxidant and anticancer properties. When consumed orally, quercetin decomposes rapidly in the early stages of digestion, and encapsulation is a strategy to ensure its bioavailability. However, O/W or W/O Pickering emulsions have limitations due to the hydrophobic phase, particularly in applications like probiotic encapsulation, production of low-calorie foods, and formulation of drugs with hydrophilic properties. On the other hand, water/water (W/W) Pickering emulsions can mimic biological environments, with stability ensured by the addition of nanoparticles capable of adsorbing at liquid-liquid interfaces. This study investigated the use of lignin extracted from sugarcane bagasse as a source of nanoparticles for stabilizing W/W Pickering emulsions formed by maltodextrin (MD) and polyethylene glycol (PEG), as well as for stabilizing O/W Pickering emulsions for the encapsulation of quercetin. The MD and PEG system was chosen due to its low cost, the ability to form two phases over a wide concentration range, and its potential for food applications. The nanoparticles were prepared from lignin obtained through alkaline and alkaline oxidative pretreatment. The alkaline oxidized lignin nanoparticles (NPLOs, 327.8 nm) were smaller than the alkaline lignin nanoparticles (NPLs, 689.8 nm). The stability of W/W Pickering emulsions formed from MD and PEG was evaluated in the presence of NPLs and NPLOs at different concentrations (0%, 0.1%, 0.3%, 0.5%, and 1%, w/w). Systems with NPLOs showed better emulsification indices and smaller droplet sizes compared to systems with NPLs. The most significant stabilization results were obtained at a concentration of 1% w/w of NPLOs, with an emulsification index of up to 63% even after two weeks. NPLs and NPLOs were also applied to stabilize O/W Pickering emulsions for the encapsulation of quercetin. In this case, the results indicated a tendency for quercetin to become trapped in the oil phase droplets. At a pH below 3, both types of nanoparticles formed agglomerates in the upper phase. NPLs demonstrated better interaction with the hydrophobic phase, enhancing the encapsulation of quercetin dispersed in this phase. The encapsulated quercetin was incorporated into food systems, and after 24 hours, high-performance liquid chromatography (HPLC) analysis showed that the concentration of quercetin added to cashew juice, in the presence of NPLs, was higher than in the condition without nanoparticles. These results suggest that lignin can be an important source of nanoparticles for stabilizing W/W and O/W Pickering emulsions, with potential applications in the encapsulation of bioactives such as quercetin in O/W Pickering emulsions.