Preparation of antimicrobial and edible films containing spirulina in different patterns and formulations and food packaging applications

In this study, bilayer films with a striped pattern and antimicrobial activity were produced using chitosan (2% w/w) and carboxymethyl cellulose (2% w/w) as the base, incorporating spirulina and three different concentrations of propolis extract (1.5%, 3%, and 6% v/v) for their antimicrobial effects. Structural characterizations of the produced films were determined by FT-IR, SEM, EDX and TGA analyses. In addition, swelling degree, water solubility, permeability, opacity, thickness, mechanical properties (tensile strength and % elongation), antioxidant activity and antimicrobial anilysis of the films were performed. Finally, the film with ideal properties was selected and applied to food packaging with cherry tomatoes (Solanum lycopersicum var. cerasiforme). The degree of swelling of the produced edible bilayer films increased as the PE concentration increased in all samples (F15 and F30) except for the F60 sample containing the highest concentration of PE compared to the control film. The water solubility ratios of the films were 62% for FK film, 71.3% for F15, 73.3% for F30 and 73.3% for F60. Optical transmittance and opacity properties of the films were evaluated separately for the transparent and colored parts of the films. Subsequently, it was determined that the colored region of the films showed good efficiency in forming a barrier against light with the spirulina doped into the structure of the film and increasing PE concentration compared to the transparent parts. The lowest opacity value in the films was found to be 0.163 ± 0.003 in the FS film, which refers to the transparent region, while the highest opacity value was found to be 1.843 ± 0.003 in the F30 film. The elongation values of the films showed the lowest value in the F30 sample containing 3% PE and the highest value in the F15 sample containing 1.5% PE. Regarding the tensile strength, it was found that the film containing 1.5% PE increased from 13.05 MPa to 15.32 MPa compared to the control and this value decreased with increasing PE concentration. The antioxidant activity of edible bilayer films increased with the increase in PE concentration and DPPH and ABTS radical scavenging activity also increased. The colored part and the transparent (FS) part of the spirulina-added (F15, F30, F60) line-patterned double-layer edible film samples containing PE at different ratios were evaluated separately and all film samples showed antimicrobial activity against E. coli, S. aureus and C. albicans. It was determined that edible bilayer films extended the shelf life of cherry tomato samples up to 21 days. As a result, with this study, edible bilayer films with antioxidant and antimicrobial properties were developed.