Lignin Nanoparticles with High Phenolic Content as Efficient Antioxidant and Sun-Blocker for Food and Cosmetics

Lignin has received significant attention as a waste product from industrial and agricultural processing, yet technical lignins are typically low in phenolic contents and its use scenarios are still largely limited. Herein, we report highly phenolic lignin nanoparticles (HP-LNPs) obtained by alkaline treatments followed by a enzymatic treatment using laccase. Urea and H2O2 were used in the alkaline treatments to enhance the LNPs with antioxidant properties and to cut down the absorption in the visible range. As a result, the HP-LNPs (N-U-L-lignin) exhibited excellent antioxidant properties, with scavenging rates of 76.12 +/- 5.64% and 51.50 +/- 4.26% for DPPH and PTIO radicals, respectively. The whiteness value of the HP-LNPs (N-H-L-lignin) increased from 43.50 to 56.39, thereby qualifying them as a natural anti-UV filler in sunscreens. We have also demonstrated, for the first time, that LNPs can be directly used for food preservation: the shelf life of fruits, such as bananas, was extended by 7 days.