Tuning the physical and functional properties of whey protein edible films: Effect of pH and inclusion of antioxidants from spent coffee grounds

This study presents a food waste valorization scheme targeting to the production of novel whey protein edible films. Initially, the effect of pH of whey protein on the physical properties of films was studied. Whey protein edible films were subsequently supplemented by an antioxidant-rich extract derived from spent coffee grounds targeting to improve the functional properties of films. The results showed significant changes at different pH, indicating that, depending on the intended application, films' properties can be controlled by shifting pH of whey protein solution. Inclusion of antioxidants resulted in edible films with UV-light resistance properties, whereas the mechanical properties and in particular tensile strength and elastic (Young's) modulus were increased. Water vapor permeability of films was considerably increased by the inclusion of antioxidants, compared to control films. Additionally, whey films enriched with phenolic compounds from spent coffee grounds presented high antioxidant activity (73.2%), which was decreased only 16.8% after a 12-month storage period. The proposed valorization scheme resulted in the development of edible films with tailor-made properties conforming with the pillars of Circular Economy.