Characterization of chitosan–nanoclay bionanocomposite active films containing milk thistle extract

• Chitosan/MMT nanocomposites incorporated with S.marinum extract (SME) were prepared.
• MMT and SME content had a great effect on the properties of films.
• Clay induces improvements in physico-mechanical and barrier properties of films.
• The films with SME showed higher antioxidant activities and lower solubility.

Nowadays, bio-based and antioxidant active packaging is attracting significant attention as one of the preferred emerging technologies to prevent sensitive oxidation of foods. In this study, chitosan/nanoclay nanocomposite active films containing three different levels of sodium montmorillonite (MMT) (1, 3 and 5% w/w based on chitosan) and Silybum marianum L. extract (SME) (0.5, 1 and 1.5% v/v) were prepared. The obtained films were characterized in terms of structural, thermal, mechanical, and barrier properties as well as antioxidant behavior. X-ray diffraction patterns confirmed the exfoliated dispersion form of MMT nanolayers. Scanning electron microscopy images showed an increase in films’ surface roughness by the addition of MMT. The results indicated that water vapor permeability and solubility of films reduced significantly (p < 0.05) by incorporation of MMT and SME. The mechanical and optical properties of films were significantly affected by the content of MMT and SME (p < 0.05). Antioxidant properties of the films also were improved by SME incorporation, suggesting that the formulated bionanocomposites could be considered as a promising antioxidant active packaging material.