Improving Oxygen Barrier Performance of Polylactide Film by Using Bleached and Unbleached Nanocellulose From Grape Pomace

ABSTRACT This study investigated two types of lignin‐containing nanocelluloses derived from grape pomace and their applications as coatings on PLA. First, bleached and unbleached grape pomace‐derived nanocelluloses (BGNC and UGNC) were extracted. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) revealed a mix of nanofibrils and well‐defined nanocrystals from BGNC and only nanofibrils from UGNC. BGNC exhibited a higher crystallinity (25.2%) compared to UGNC (20.2%), both with preserved native cellulose type I structure. Thermogravimetric analysis (TGA) showed that residual lignin was present in both samples although strongly reduced after bleaching. BGNC or UGNC coatings were applied via bar‐coating at theoretical thicknesses of 90, 140, and 1540 nm. Due to its higher lignin content, the UGNC‐coated surface was more hydrophobic, an interesting property for packaging, while the BGNC‐coated film showed better oxygen barrier properties thanks to its higher crystallinity and more uniform coating. BGNC‐coated film exhibited a good oxygen barrier with a permeability (OP) of 5.91 × 10 −19 m 3 m/m 2 s Pa at 90 nm thickness, while the UGNC‐coated film only reached 9.40 × 10 −19 m 3 m/m 2 s Pa. The oxygen barrier and hydrophobicity are both promising features, highlighting the potential application of by‐product‐derived nanocelluloses for bio‐based, compostable food packaging and the interest of lower‐impact chemical extractions to develop original properties.