Comparative Evaluation of Biocontrol Strategies against Listeria monocytogenes Contamination in Fresh Produce

Abstract:

The historical reliance on chemical sanitizers for controlling Listeria monocytogenes contamination in fresh produce has increasingly been questioned due to concerns regarding chemical residues, environmental sustainability, and the emergence of sanitizer-tolerant strains. This research aimed to evaluate and compare the efficacy of six biocontrol strategies against L. monocytogenes contamination in fresh produce commodities under simulated commercial storage conditions in Lagos, Nigeria. A randomized controlled experimental investigation was conducted from June 2022 to May 2023 at the Lagos Academy of Agricultural Sciences. Six treatment modalities were evaluated: bacteriophage P100 (10⁸ PFU/mL), nisin (2500 IU/mL), Lactobacillus plantarum protective culture (10⁸ CFU/mL), Pediococcus acidilactici fermentate, citric acid wash (2%), and sodium hypochlorite (200 ppm) as the conventional control. Treatments were applied to lettuce, tomato, and cucumber samples artificially inoculated with a five-strain cocktail of L. monocytogenes at approximately 10⁵ CFU/g and monitored over 72 hours at 4°C and 10°C. Bacteriophage P100 demonstrated the greatest overall efficacy with a mean log reduction of 4.2±0.3 log CFU/g at 4°C after 72 hours, followed by nisin (3.6±0.4 log CFU/g) and L. plantarum (3.1±0.5 log CFU/g). The combination of bacteriophage P100 and nisin exhibited synergistic antimicrobial activity, achieving 5.1±0.2 log reduction, significantly exceeding all individual treatments (p<0.001). Temperature significantly influenced treatment efficacy, with all biocontrol agents demonstrating superior performance at 4°C compared to 10°C (p<0.05). Sensory evaluation revealed no significant adverse effects on produce quality for any biocontrol treatment. These findings support the integration of bacteriophage-based biocontrol strategies, particularly in combination with nisin, as effective and sustainable alternatives to chemical sanitization for controlling L. monocytogenes in fresh produce supply chains across West Africa.