Sustainable Cellulose Nanofiber Films from Carrot Pomace as Sprayable Coatings for Food Packaging Applications

In order to limit the excessive use of nonrenewable plastics as materials for food packaging, research into the development of more environmentally friendly packaging materials and practices has grown rapidly over the past few decades. Although cellulose nanofibers (CNF) have emerged as a promising material for such purposes, typically commercial producers utilize already valorized lignocellulosic sources such as wood pulp for CNF production. This can have significant cost implications, and therefore the use of alternative lignocellulosic sources, such as wastes from agricultural processing, is of high interest. Herein, we investigate the use of carrot pomace from both fresh and stale carrots, sourced as agricultural waste (unsellable for retail) from a local Swiss vegetable producer to produce CNF. The use of a one-pot bleaching pretreatment and the energy required for homogenization of the carrot pomace along with the resulting CNF fiber morphology and quality (surface area, degree of polymerization, carbohydrate content) are analyzed. In addition, model films are prepared via vacuum filtration and hot-pressing, whereby film quality, as related to morphological, optical, mechanical, and barrier properties, is assessed. Finally, carrot CNF suspensions are sprayed onto the surface of bananas, demonstrating a substantial delay in enzymatic browning for up to 1 week. The results presented herein represent a significant advancement in the development of sustainable materials for food packaging.