Biocontrol of Listeria monocytogenes ATCC 7644 on fresh-cut tomato (Lycopersicon esculentum) using nisin combined with organic acids.

The biocontrol of Listeria monocytogenes on fresh-cut tomato using nisin and organic acids was investigated. Fresh-cut samples inoculated with 108 CFU/mL of L. monocytogenes, treated with nisin (5,000 IU/mL), a combination of nisin and organic acids (acetic and citric acids at 3 and 5% each), with chlorine at 200 ppm as a control, and stored for six days at 4, 10, and 25°C were used to evaluate certain physicochemical qualities (pH, titratable acidity, soluble solid content, vitamin C content, and color). Nisin treatment significantly (p<0.05) reduced bacterial population by 1.91-3.07 log CFU/mL. Nisin-citric acid combination provided 2.65-3.29 log CFU/mL reduction, while nisin-acetic acid combination provided 2.93-4.15 log CFU/mL reduction. The control treatment provided <1-2 fold log reductions. Slight variations in physicochemical properties of fresh-cut tomato were observed. Nisin and organic acids can be used to improve the microbial safety of fresh-cut tomato.