Trisodium phosphate enhanced phage lysis of Listeria monocytogenes growth on fresh-cut produce

•Bacteriophage reduced Listeria monocytogenes on fresh-cut tomatoes and watermelon.•Trisodium phosphate at 30 and 60 mg/ml significantly enhanced phage lysis against L. monocytogenes.•Combination treatment did not affect color parameters of both fresh produce sample.

Combination of bacteriophage and trisodium phosphate (TSP) to inactivate Listeria monocytogenes inoculated on fresh-cut produce was investigated. Fresh-cut tomato and watermelon inoculated with L. monocytogenes cocktail at log 107 CFU/g were treated with Listex P100 bacteriophage (108 PFU/g) alone, and in combination with TSP at 10, 30 and 60 mg/ml using chlorine at 200 mg/L as control. Treated samples were stored at 4 and 10 °C for 6 days. Effect of treatment on pH and colour of treated samples was evaluated. Phage treatment alone significantly (p < 0.05) reduced L. monocytogenes on fresh-cut tomato by approximately 0.5 and 0.6 log CFU/ml and on fresh-cut melon by 1.30 and 1.49 log CFU/ml at 4 and 10 °C respectively. Addition of phage-TSP at 10 mg/ml was only effective on fresh-cut melon, but phage-TSP at 30 and 60 mg/ml approximately reduced inoculated tomato by 1 and 2 logs, and melon by 2 and 5 logs at 4 and 10 °C respectively. Chlorine treatment showed 1-2 log reduction. Phage titer declined rapidly on tomato unlike melon, pH and colour parameters slightly increased with treatment combinations with no impairment on both samples. Phage-TSP combination could serve as effective tool to control listeriosis outbreak in fresh produce.