Pearl millet starch-based films reinforced with lignocellulose nanofibers (LCNFs) from peach pits

In the present study, lignocellulose nanofibers (LCNF) with two different lignin concentrations (5% and 7%) were successfully extracted from peach pits through a sequential and controlled process. Peach pits are used for the first time to isolate LCNF. This process involved bleaching of ground peach pits, alkali treatment, and mechanical fibrillation using a planetary ball mill to yield nanoscale fibers with diameters ranging between 3 and 5 nm. The LCNFs obtained through bleaching with 8% NaClO₂ had 7% lignin content and were designated as LCNF-7, while those treated with 16% NaClO₂ had 5% lignin and were referred to as LCNF-5. Further, pearl millet starch was isolated using the wet milling method, and reinforced with LCNFs containing 5% and 7% lignin to develop nanocomposite films. The films were printed with the Clemson Tigers logo and exhibited excellent print quality, with clear reproduction of the distinctive orange and purple hues of the logo. Subsequently, the films were evaluated for their physical, mechanical, and barrier properties, and the starch-based films reinforced with LCNFs containing 7% lignin (L7) exhibited significant improvements. Specifically, the tensile strength and Young's modulus of the L7 reinforced films increased by 7 times and 14 times, respectively, compared to the control starch films. The crystallinity of L7-50 films was recorded as approximately 16.8%, whereas the control films showed crystallinity of about 4%. Moreover, the thermal resistance of the L7 film was slightly higher than that of the control film. The water vapor transmission rate of the L7-50 film decreased from 173 g/(m²·day) to 150 g/(m²·day), suggesting an improvement in barrier performance. Peach pits are used for the first time to isolate LCNF, and these findings provide both theoretical insights and experimental validation for the development of multifunctional, printable, and sustainable films reinforced with LCNFs.