Combined effect of γ-irradiation and antibacterial formulations based on natural compounds for preservation of mother's milk

Abstract

The antibacterial potential of citrus extract, EOs (mediterranean formulation, oregano, lemongrass, cinnamon and clove), organic acids and salts (citric acid, lactic acid and sodium carbonate) was evaluated against E. sakazakii, E. coli O157:H7, S. aureus, L. monocytogenes, S. Typhimurium, B. cereus by determining the minimal inhibitory concentration (MIC). Based on the results, MIC value ranges from 312.5 to 5000 ppm against tested bacterial strains, with citrus extract showing the highest antibacterial activity (312.5 ppm). Four antimicrobial formulations based on quaternary combination of compounds were developed based on the fractional inhibitory concentration (FIC) index. Formulation 1 (Oregano/Mediterranean formulation/Citrus extract/Lactic acid), Formulation 2 (Cinnamon/Lemongrass/Citrus extract/Citric acid), Formulation 3 (Oregano/Mediterranean formulation/Citrus extract/Citric acid), Formulation 4 (Cinnamon/Lemongrass/Citrus extract/Lactic acid) showed a synergistic effect against all tested pathogens. Results demonstrated that bacterial radiosensitivity (1.34–3.99) was increased by the combined treatment of γ-irradiation with developed formulations in frozen mother's milk. Formulation 3 and 4 induced greater radiosensitivity in bacterial strains including sporulated B. cereus (1.90 and 1.89 respectively) compared to formulation 1 and 2. Therefore, the combined treatment can be an effective method to reduce the γ-irradiation dose (kGy) required to eliminate the pathogens and assures the safety of frozen mother's milk.