Antimicrobial Olive Leaf Gelatin films for enhancing the quality of cold-smoked Salmon

Abstract Olive leaf was evaluated as antimicrobial/antioxidant ingredient in edible films intended for cold-smoked fish preservation. Olive leaf powder (OLP) and its water/ethanol extract (OLE) were previously tested against Listeria monocytogenes , Escherichia coli O157:H7 and Salmonella enterica. Antimicrobial and antioxidant capacity, color and water vapor permeability (WVP) of OLE-gelatin films (0, 1.88, 3.75 and 5.63% w/w) were determined. OLP and OLE showed antibacterial activity against L . monocytogenes in agar diffusion tests, and non-effect was observed on E. coli and S. enterica . Antimicrobial and antioxidant activities of the films increased with increasing OLE concentration in their formulations. Film lightness was not significantly affected by OLE. In contrast, a * decreased and b * increased with increasing OLE concentration. Addition of 3.75 and 5.63% of OLE also increased WVP of the films. A film formulation with 5.63% OLE was considered optimal for further tests against L. monocytogenes in inoculated cold-smoked salmon. The films significantly reduced the growth of this pathogen on the fish over storage.