Synergistic Antimicrobial Effects of Nisin and ε-Poly-L-Lysine on Raw Beef During Cold Storage Against Major Foodborne Pathogens

With increasing consumer demand for natural food preservatives, the use of antimicrobial substances such as nisin and epsilon-poly-L-lysine (ε-PL) in meat products has gained attention. This study aimed to evaluate the synergistic effects of nisin and ε-PL on the viability of key foodborne pathogens—Escherichia coli O157:H7, Salmonella Typhimurium (Gram-negative), and Listeria monocytogenes (Gram-positive)—in raw red meat. In addition, the study evaluated the impact of treatments on physicochemical characteristics and color stability. Two combinations of nisin and ε-PL were tested: Mix 1 (400 IU/g nisin + 20 μg/g ε-PL) and Mix 2 (800 IU/g nisin + 40 μg/g ε-PL), applied to raw beef samples inoculated with the pathogens. Samples were stored at 4 °C for 16 days, and microbiological (pathogen counts, total mesophilic aerobic bacteria, mold, and yeast), physicochemical (pH, water-holding capacity), and color (L*, a*, b*) analyses were performed at intervals (days 0, 4, 8, 12, and 16). Mix 2 showed the most potent antimicrobial activity, decreasing L. monocytogenes counts to 2.15 log CFU/g by day 8. Significant reductions were also recorded for E. coli O157:H7 and Salmonella Typhimurium. Additionally, the mixtures suppressed pH increases, maintained color stability, and improved water retention. In conclusion, the free-form combinations of nisin and ε-PL effectively inhibited microbial growth, preserved meat quality, and extended shelf life, highlighting their potential as natural preservatives in the meat industry. This study provides novel evidence on the synergistic use of free-form nisin and ε-PL in raw beef, offering a valuable contribution to the development of natural preservation methods in meat products.