ANTIMICROBIAL ACTIVITY OF EGG WHITE PROTEIN-BASED EDIBLE FILMS INCORPORATED WITH THYME AND HOPS LIQUID EXTRACTS ON HAMBURGERS

Antimicrobial activity of egg white protein-based edible films (EWP) incorporated with 5% thyme (TV), 5% hops (HL), and 2.5% thyme + 2.5% hops (TH) liquid extracts was evaluated on hamburgers during refrigerated storage (4 °C). Physical properties such as color and thickness of the films were determined, and according to the results, it was determined that the addition of the extract decreased the L* value, increased a* and b* values, slightly increased the thickness value in the films. The average total viable count, yeast-mold, coliform group bacteria, Staphylococcus spp., and Pseudomonas spp. numbers of the hamburgers varied between 6.12-8.43 log CFU/g, 2.50-5.46 log CFU/g, 4.87-7.35 log CFU/g, 4.15-6.17 log CFU/g, and 6.10-9.22 log CFU/g, respectively. The groups with hops extract supplements have always had the lowest number of coliforms, indicating that hops extract has higher antimicrobial activity on the coliform group bacteria compared to especially the control group (p<0.05). The film application reduced the brightness, and the thyme extract increased the yellowness in the hamburgers. The redness was not affected by storage and treatment factors. While the pH value is very close to each other in the film-packaged groups, it exhibits a constantly increasing slope in the control group. Abbreviations: C, control group unpackaged with film; EWP, antimicrobial-free film; TV, 5% (v/v) thyme (Thymus vulgaris L.) extract added film; HL, 5% (v/v) hops (Humulus lupulus L.) extract added film; TH, 2.5% (v/v) thyme extract + 2.5% (v/v) hops extract added film