Structure-property relations of TEMPO-oxidized bamboo nanocellulose-based aerogels and films in food packaging applications.

Bamboo, as a renewable biomass resource, presents significant potential for sustainable food packaging applications. In this study, cellulose nanofibrils were extracted from bamboo powder via sequential acid/alkali purification, TEMPO oxidation, and high-intensity ultrasonication. The resulting bamboo oxidized nanocellulose (BONC) was fabricated into aerogels via ice-templating and into films via casting to systematically investigate their fundamental properties. Purification effectively increased cellulose content from 56.29% to 95.71% by removing lignin and hemicellulose, while preserving the cellulose I crystalline structure. Oxidation enhanced dispersion and reduced the average fibril diameter from 13.45 nm (BNC) to 7.38 nm (BONC). For aerogels, increasing suspension concentration elevated density and compressive strength while reducing porosity. Lower freezing temperatures (-196 °C) yielded finer, more uniform pores, enhancing thermal insulation and structural integrity; conversely, directional freezing (DF) induced anisotropic architectures with superior axial mechanical strength but inferior thermal insulation. Notably, the high porosity (> 99%) and interconnected channels of aerogels resulted in excessive gas permeability and water absorption, precluding their standalone use as modified atmosphere layers. In contrast, BONC films exhibited concentration-dependent barrier properties, with the 1.0 wt% film reducing O₂ to 18.9% and increasing CO₂ to 3.67%. Therefore, the two forms of packaging materials can serve different purposes. These results establish a fundamental understanding of processing-structure-property relationships in bamboo-derived nanocellulose materials and lay an experimental foundation for the development of high-performance food packaging materials.