Rapid assessment of the effectiveness of antioxidant active packaging—Study with grape pomace and olive leaf extracts

Natural antioxidants are mixtures of different components with their specific partition and diffusion coefficients and the exact description of the release kinetics into foods is, therefore, complex. For practical application however, the interest should be focused on the antioxidant effect rather than on the single compounds release, i.e., it is an approximation to describe the release of a mixture by treating it as single substance. The evaluation of such approach was subject of this study. Film samples coated with Shellac (Shel) and cellulose nitrate (NC), containing olive leaf extract (OLE) and grape pomace extract (GPE) at different concentrations were put in contact with three food simulants, namely W (water), A (10% ethanol) and D1 (50% ethanol), and the antioxidant capacity was assessed by suitably modified ABTS test. The equilibrium antioxidant capacity increased from W to A and D1 for GPE and OLE: the antioxidant levels attained films containing GPE were 0.272, 0.483 and 0.728 Trolox mEq/L at 5% concentration, and 0.705, 0.786 and 0.893 Trolox mEq/L at 10% concentration for W, A and D1 simulants, respectively. The method was also effective at comparing the lacquer retention performances, NC being more effective than the Shel, i.e., it showed a faster release of antioxidant compounds.