Modulation of physicochemical and antioxidant properties of Pickering emulsions using colloidal lignin particles based on kraft softwood and hardwood acetone fractions

Colloidal lignin particles (CLPs) emerge as a sustainable alternative to traditional, fossil-based emulsion stabilizers. However, effectively outperforming the conventional ingredients requires addressing the challenges posed by lignin heterogeneity and structural complexity. In this study, one-step acetone fractionation was applied to softwood and hardwood kraft lignins to tackle the issue. The resulting soluble (AS) and insoluble (AI) fractions, along with the pristine lignins, underwent thorough characterization and were used to create CLPs through the hydrotropic precipitation. The acetone fraction-derived CLPs were tested for the first time as Pickering stabilizers. Notably, a strong correlation emerged between the structural traits of each lignin sample and the properties of the resulting Pickering emulsions. Such correlation allowed for a fine-tuning of their physicochemical and antioxidant features. The AS fractions, characterized by higher phenolic OH content and lower molecular weight, led to CLPs with larger sizes and reduced hydrophilic character compared to those derived from AI- and pristine lignins. The fraction-derived CLPs exhibited superior emulsifying capacity and imparted long-term stability to the formed emulsions. Moreover, the resulting Pickering emulsions showed high potential as antioxidant agents, proving their ability as multifunctional systems. Overall, this work demonstrates how the unique properties of lignin can be selectively enhanced through acetone fractionation method and seamlessly transferred to Pickering emulsions. This advancement promotes the use of lignin in high-value-added sectors such as cosmetics and personal care.