Modeling the Inactivation of Listeria innocua and Escherichia coli in Fresh-Cut Tomato Treated with Pulsed Light

The effectiveness of pulsed light (PL) treatments to inhibit microorganisms on fresh-cut tomatoes (Lycopersicon esculentum Mill., cv. Daniela) was investigated. Tomato slices inoculated with Escherichia coli or Listeria innocua were exposed to PL treatments (4, 6, or 8 J cm(-2) fluence) and kept cold at 4 A degrees C for 20 days. L. innocua and E. coli counts, gases in the headspace of the containers (O-2 and CO2), pH, titratable acidity, and soluble solid content were monitored throughout the cold storage. The PL treatments reduced significantly (p < 0.05) initial loads of both microbes. The effect of the PL fluence on the survival number of microoganisms was described by a log-linear model (R (2) = 0.849-0.999). At any fixed time within the cold storing, the microbial counts for untreated samples were always higher than those cut tomatoes that had been previously PL-treated. The behavior of L. innocua and E. coli during the storage were well adjusted (R (2) > 0.930) by Gompertzian models; the studied microorganisms exhibited different patterns during the storage period. On the other hand, O-2 and CO2 partial pressures in containers with fresh-cut tomatoes were also significantly affected by PL treatments (p < 0.05). The highest PL fluence caused the greatest changes of O-2 and CO2 contents. In addition, the application of PL triggered an acceleration of the O-2 consumption during the cold stage. PL treatments might be used to effectively extend the safety of fresh-cut tomatoes over 12 days of storage against E. coli and L. innocua growth.