Apple Peel Extract-Loaded Fish Skin Gelatin/PVA Films: Functional Properties and Soft Cheese Application

• 1Abeer Majeed

  Author

[Background and Objectives: Active packaging films that utilize natural antimicrobial and antioxidant agents are a promising alternative to traditional synthetic preservatives; the aim of this study was to fully characterize active films produced with fish skin gelatin (FSG) and polyvinyl alcohol (PVA) containing varying levels of apple peel extract (APE), which is rich in polyphenolic compounds, and determine the effectiveness of these active films in extending the shelf life of soft cheese during refrigerated storage. Methods: Active films were created containing 0%, 1%, 2%, and 3% APE by mass; the characterization of the films included assessment of physicochemical properties (i.e., thickness, moisture content, water vapor permeability [WVP], solubility), mechanical properties (i.e., tensile strength [TS], elongation at break [EAB], Young's modulus), thermal characterization ((thermal analysis using differential scanning calorimetry [DSC] and thermogravimetric analysis [TGA]), structural characterization (Fourier transform infrared [FTIR] and X-ray diffraction analysis [XRD]), and optical characterization. Antimicrobial efficacy was determined using minimum inhibitory concentration (MIC), agar disc diffusion, and challenge studies on Listeria monocytogenes and Staphylococcus aureus. The release kinetics of polyphenols from the packaging films were estimated using food simulants (3% acetic acid and 10% ethanol) and the modeling was done according to the European Union Regulation No. 10/2011. To determine the efficacy of each film to extend the shelf life of soft cheese, soft cheese wrapped in each of the films was evaluated after 28 days of storage at 4°C by microbiological analysis, based on chemical parameters, thiobarbituric acid (TBA) analysis, and sensory properties evaluated using a 9-point hedonic scale. Total migration of packaging material into soft cheese was determined based on Saudi Food and Drug Authority (SFDA) and European Food Safety Authority (EFSA) regulations. Results: Listeria monocytogenes MIC and Staphylococcus aureus MIC were 6.25 mg/mL and 3.13 mg/mL, respectively, when tested against APE solutions; an increase in antioxidant activity (87.4 ± 1.2%) as measured with 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was observed at the highest concentration (3%) of APE; the WVP of the films with APE was significantly lower (1.82 ± 0.09 × 10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹) at the 3% APE level; and the TS of the films with APE was significantly higher at the 3% APE level (18.6 ± 0.7 MPa). The thermal analysis supported an increase in thermal stability of the films, as indicated by DSC data, where the melting temperature (Tm) of the films with no APE was 68.2°C, while the Tm of the films containing 3% APE was 74.1°C. The decrease in the crystallinity index of the active films, from 42.3% to 28.6%, measured by XRD analysis supports an even distribution of the polyphenols within the active films.

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