Lignin particles as a possible carrier for bioactive in food industry

There is a growth interest by industry and scientific community in find natural polymers with potential to replace synthetic ones. In this sense, lignin, a byproduct of pulp and paper industry, has been highlighted due to its intrinsic properties, such as antimicrobial, antioxidant and chemical structure that enable its functionalization. The aim of this study was to evaluate the production of lignin particles through solvent shifting method to further encapsule an active and applied it into food. Kraft lignin was added to an 70.0 % and 75.0% ethanol solution, with final concentration of 10 mg.mL-1 and 4.60 mg.mL-1, respectively. After solubilization, the solution was filtered, Mili-Q® water was added and the solution stirred overnight to form the lignin particles. The removal of ethanol was performed by evaporation. Size and zeta potential of the lignin nanoparticles were performed in a ZetaSizer Nano-ZS (Malvern Instruments, United Kingdom) at 25 °C, immediately and 30 days after particle formation. The particle size was 95.19 nm and zeta potential -28.1 mV to particles formed from ethanol 70.0 % and final concentration of 10 mg.mL-1. For particles formed from ethanol 75.0 % and final concentration of 4.60 mg.mL-1, particle size and zeta potential were lower (49.02 nm and -32.26 mV). After 30 days, particles made in ethanol 70.0 % showed a slight increase in size (110.0 nm) and zeta potential remained the same (-29.26mV). On the other hand, particles made in ethanol 75.0 % showed the same size (50.36 nm) and a slight increase in zeta potential (-35.56 mV).
These results show the hydrophilicity of the solvent is important to solubilize lignin and consequently to form the particles, since among the forces that driven the self-assembly are the hydrogen bonds. The slight modifications both in size and zeta shows a stable system. In addition to system stability, as the solvent used was ethanol, which is widely used in food industries, the methodology proposed in this study shows a great potential to be used to encapsule bioactive aiming future applications in food industry.