A novel bio-based time-temperature dependent colorimetric indicator film incorporated with Amaranthus leaf extract for beef freshness tracking

Leveraging amaranthus leaf extract (ALE) as an indicator, polyvinyl alcohol (P), and citric acid (C) as film fabricating materials, an innovative time-temperature indicator (TTI) for beef freshness tracking film, known as PC-ALE was successfully created. The films were characterized in terms of their kinetic modeling, molecular properties, morphological characterization, and physiochemical properties. Arrhenius model was made by utilizing the colorimetric values of TTI films collected from −10 to 35 °C. The correlation coefficient and activation energy of the fitting model were 0.9467, 0.9399, 0.6886, and 123, 57, 95 kJ.mol⁻¹ for ALE containing films with 0.250, 0.375, and 0.500 g, respectively. However, Fourier transform-infrared spectroscopy spectra showed interactions between the molecules. Mechanical properties of the TTI films showed that the addition of ALE enhanced its tensile strength (99.58 to 139.23 MPa) and elongation at break (151.25 to 216.35 %). Due to its optimal colorimetric response, best-fitting reaction kinetic model (R² = 0.9399), significant time-temperature sensitivity, and balanced mechanical properties, PC-ALE-0.375 films are the most suitable for monitoring beef freshness.