Cellulose nanocrystals (CNC) were mixed with either cellulose nanofibril (CNF) or carboxymethylcellulose (CMC) in variable proportions (0/100, 20/80, 40/60, 50/50, 60/40, 80/20 and 100/0) to obtain cast films with acceptable barrier and mechanical properties as replacements for food packaging plastics. Both CNF and CMC improved tensile strength, elongation, UV opacity, air resistance, hydrophobicity (WCA-water contact angle), water vapor transmission rate (WVTR) and oxygen impermeability in pure CNC. WVTR and oxygen permeability were strongly dependent on relative humidity (RH). Interestingly, the greatest effect on WVTR was observed at RH = 90% in films containing CMC in proportions above 60%. CMC- and CNF-containing films had oxygen impermeability up to an RH level of 80% and 60%, respectively. The previous effects were confirmed by food packaging simulation tests, where CMC-containing films proved the best performers. The composite films studied were biodegradable-which constitutes a major environmental related advantage-to an extent proportional to their content in CMC or CNF.

Preparation of nanocrystalline cellulose (NCC) by 62 and 65 % wt. sulfuric acid hydrolysis of cellulase-pretreated fibers was optimized to obtain the highest yield by applying two statistical plans. At optimal conditions (10 U/g odp cellulase, 25 min hydrolysis, 47 °C, 62 wt.% H₂SO₄), high yields (≥80 %) were obtained, including an increase of ~9 points due to the enzyme. Optimal conditions produced nanosized particles of around ~200 nm with reduced surface charge and sulfur content. The optimization allowed reduction of hydrolysis time by 44 % and increase of yield by more than 10 points compared with results in previous work. The effects of cellulase pretreatment were noticeable even under aggressive hydrolysis conditions, emphasizing its possibilities. Zeta potential and polydispersity index indicated that all studied conditions led to good-quality final products, with values around −50 mV and 0.2, respectively. Transmission electron microscopy (TEM) analysis confirmed the presence of NCC. Fourier-transform infrared (FTIR) spectroscopic analysis provided evidence that cellulase treatment increased the crystallinity of both cellulose fibers and NCC, as well as fiber accessibility, supporting the other analyses of NCC.