PH-Responsive Sodium Alginate Edible Films Incorporated with Grape Seed Proanthocyanidins and Thyme Essential Oil for Pork Preservation

To meet the demand for edible packaging materials that possess both pH-responsive properties and antibacterial performance in the field of meat preservation, this study developed an edible GSP-TEO-SA film using sodium alginate (SA) as the film-forming substrate, thyme essential oil (TEO) as the antibacterial agent, and grape seed proanthocyanidins (GSP) as the pH-responsive component. The effects of GSP and TEO addition on the structure, mechanical properties, antioxidant activity, and antibacterial activity of the edible film were systematically evaluated, and its practical application effectiveness in pork preservation was investigated. The results indicated that the addition of 0.5% GSP significantly enhanced the tensile strength, UV barrier properties, and antioxidant efficacy of the edible film (p < 0.05). The incorporation of 1% TEO increased the hydrophobicity of the film. When GSP and TEO were present simultaneously, the tensile strength and elongation at break of the film increased to their maximum values, reaching 3.81 ± 0.04 MPa and 57.76 ± 1.97%, respectively. Furthermore, the film exhibited the lowest water vapor transmission rate and the largest contact angle of 65.70°. Fourier transform infrared spectroscopy and thermogravimetric analysis revealed altered or strengthened hydrogen-bonding interactions within the GSP-TEO-SA film, leading to a denser and more stable structure. In pork preservation applications, both the GSP-SA film and the GSP-TEO-SA film exhibited color changes, with the most pronounced alteration observed in the GSP-TEO-SA film. Meanwhile, during storage, the GSP-TEO-SA film effectively inhibited the increases in pH, TVB-N content, and total viable count. In conclusion, the GSP-TEO-SA film holds great promise for meat preservation applications.