Smart Packaging for Food Spoilage Assessment Based on Hibiscus sabdariffa L. Anthocyanin-Loaded Chitosan Films

An on-package colorimetric label was fabricated using Hibiscus sabdariffa L. anthocyanin as a freshness indicator because its color depends on pH. The anthocyanins were embedded within a chitosan matrix. The colorimetric labels were applied to estimate the spoilage of fish food during storage at 25 °C for 3 days. According to scanning electron microscopy results, the inclusion of the anthocyanins in chitosan matrix resulted in formation dense and uniform film. The chitosan colorimetric labels had acceptable thicknesses (78–85 µm), moisture contents (14–16%), swelling indices (84–102%), water vapor permeabilities (3.0–3.2 × 10−11 g m/m2 s Pa), tensile strengths (11.3–12.3 MPa), and elongation at breaks (14–39%). It is noteworthy that the label can distinguish fish spoilage by color turn from light brown (fresh) to grayish (spoiled) by the naked-eye, due to alterations in the pH content and formation of volatile basic nitrogen during storage. Our results indicate that all-natural color labels can be an effective method to monitor the fish spoilage during storage, which may improve food quality and sustainability.