Recent advance on lignin-containing nanocelluloses: The key role of lignin

Nanocelluloses (NCs) isolated from lignocellulosic resources usually require harsh chemical pretreatments to remove lignin, which face constraints such as high energy consumption and inefficient resource utilization. An alternative strategy involving the partial retention of lignin can be adopted to endow NCs with better versatility and functionality. The resulting lignin-containing nanocelluloses (LNCs) generally possess better mechanical property, thermal stability, barrier property, antioxidant activity, and surface hydrophobicity than lignin-free NCs, which have attracted extensive interest as a promising green nanomaterial for numerous applications. This review provides a comprehensive overview of the recent advances in the preparation, properties, and food application of LNCs. The effect of residual lignin on the preparation and properties of LNCs is discussed. Furthermore, the key roles of lignin in the properties of LNCs, including particle size, crystalline structure, dispersibility, thermal, mechanical, antibacterial, rheological and adhesion properties, are summarized comprehensively. Furthermore, capitalizing on their dietary fiber and nanostructure properties, the food applications of LNCs in the forms of films, gels and emulsions are also discussed. Finally, the challenges and opportunities regarding the development of LNCs are provided.