Biodegradable Nanocomposite Film Based on Gluten/Silica/Calcium Chloride: Physicochemical Properties and Bioactive Compounds Extraction Capacity

In this study, a biodegradable wheat gluten (WG) film containing calcium chloride and nano silica (WG/CaCl 2 /SiO 2 ) was prepared and the physicochemical properties of the film were investigated. Finally, the WG/CaCl 2 /SiO 2 film was used as a polymeric adsorbent for extraction of bioactive compounds from red grape pomace. The properties of the composite film, including thickness, water vapor permeability (WVP), solubility, antioxidant activity and mechanical property were investigated. FT-IR, SEM, XRD and DSC tests were performed to investigate the physical, morphology and thermal properties of film. The results showed that the addition of SiO 2 decreased the WVP because these nanoparticles can fill the porous cavities of the film matrix. Furthermore, SiO 2 caused to improve the water resistance of the film. With the addition of SiO 2 , the antioxidant content of the films increased compared to the control film. The addition of SiO 2 to the film decreased the crystal property and addition of CaCl 2 increased the crystal property of the film. In the second step, the optimum film as adsorbent was used to extract of the bioactive compounds from the red grape pomace. For this purpose, total phenol, flavonoid and anthocyanin content were measured before and after the extraction by film, and the optimum extraction conditions were obtained by the desirability function method. At optimum extraction condition, the phenolic compounds were extracted with 76.9% efficiency and optimum extraction temperature and time were 20.5 °C and 27.1 h, respectively. Due to the low solubility of WG/CaCl 2 /SiO 2 film in water and its appropriate thermal and mechanical stability, the WG/CaCl 2 /SiO 2 film in different aquatic environments can be used to extract bioactive compounds of fruit pomace.