Multilayer films based on starch and nanocellulose extracted from taro: Evaluation of carvacrol incorporation in the inner layer and application as active separators for Paipa cheese.

Multilayer systems are an innovative strategy to improve biodegradable polymers and incorporate active compounds. In the current work, taro starch-cellulose nanofiber (CNF) three-layer films, consisting of two outer starch-CNF layers and an inner starch layer containing 0, 5, or 10% carvacrol, were developed as biodegradable active separators for Paipa cheese slices. Carvacrol incorporation promoted pores, cracks, and microstructural heterogeneity. Besides, carvacrol increased surface wettability, reducing the water contact angle from 45.44° to 34.97°, but did not significantly affect water vapor permeability (7.06 to 8.17 × 10-10 g·s-1·m-1·Pa-1), transparency (6.9 to 7.2 a.u./mm), swelling (51.9 to 53.9%), water solubility (17.6-19.4%), or moisture content (20.3-22.7%). Tensile strength decreased from 10.05 ± 0.14 MPa in the control film to 3.91 ± 0.15 and 6.49 ± 0.30 MPa in films with 5 and 10% carvacrol, respectively, while elongation at break decreased from 36.48 ± 1.28% to values near 15-16% in the active films. Carvacrol-containing films released the active compound into 50% ethanol, reaching a plateau after approximately 8 h, and showed DPPH radical-scavenging capacity of 7.77-8.00 μmol TE/g film. When applied to Paipa cheese, the separators did not intensify color changes during refrigerated storage but reduced lipid oxidation after 30 days, with TBARS values decreasing from 1.76 mg MDA/kg in control cheese to 0.62 and 0.56 mg MDA/kg in cheeses stored with 5 and 10% carvacrol films, respectively. These results indicate the potential of taro starch-CNF multilayer films as antioxidant biodegradable separators for semi-ripened cheese slices.