Silver Gelled Chitosan Films: Preparation, Inclusion of Sunflower Seed Oil, and Application in Bread Packaging

Abstract

Silver gelled chitosan (CS-Ag) films with improved mechanical traits were prepared via a simple technique, which comprised freezing the CS solution, and then pouring the AgNO₃ solution onto it. This resulted in the creation of uniform and mechanically stable CS-Ag films due to the slow diffusion of AgNO₃ into the frozen solid CS. The films were characterized via scan electron microscopy (SEM) and energy-dispersive X-ray (EDX). Their antimicrobial and mechanical traits were inspected. The tensile strength (TS) of the 1.5% (w/w) AgNO₃ processed CS-Ag films reached 22.42 ± 0.89 MPa and its elongation at break was 33.01 ± 2.67%. The water vapor transmission rate (WVTR) of this film was also inspected and it was 167.77 g/m²day. This value was reduced to 146.95 and 120.68 g/m²day, after the inclusion of sunflower seed oil (SFO) within the CS-Ag films at 5% and 8% (w/w), respectively, and this reflected the increased water resistance of the SFO-CS-Ag films. The inclusion of SFO at concentration ≥ 5% (w/w) also increased the films antimicrobial traits when Aspergillus and Rhizopus species were inspected. On the other hand, the TS of the SFO-CS-Ag films was reduced to 15.13 ± 1.61 MPa and 10.17 ± 0.77 MPa for the 5% and 8% SFO, respectively. Nonetheless, these values were still within 8.3–31.4 MPa TS range of the frequently utilized packaging material; low-density polyethylene. Thus, the 5% and 8% (w/w) SFO-CS-Ag films were utilized to package white bread. The 8% (w/w) SFO-CS-Ag film efficiently preserved bread as no fungal growth observed for 10 storage days.