Inactivation of Salmonella in cherry tomato stem scars and quality preservation by pulsed light treatment and antimicrobial wash

The objective of this study was to evaluate the effectiveness of pulsed light (PL) treatment, a novel antimicrobial (LAPEN) wash and combinations thereof in inactivating Salmonella on stem scars of cherry tomato. The treatment effects on background microbiota and sensory quality was also investigated while in storage for 21 days at 10 degrees C. Three serotypes of Salmonella enterica were chosen to prepare inoculum for the current investigation for their link with tomato and produce outbreaks. Stem scars of tomato were spot inoculated before being treated with PL (1-63 J/cm(2)), LAPEN sanitizer (2 min) or combinations of PL with LAPEN Sanitizer. Significant inactivation was observed at low doses of PL. A 30 s treatment equivalent to a dose of 31.5 J/cm(2), was found optimal. The optimal dose provided 2.3 log reduction of Salmonella while a 2 min wash in LAPEN sanitizer provided 2.1 log CFU/g reduction on stem scars. Two possible sequences of PL and LAPEN combinations were explored. For PL-LAPEN combination, inoculated tomatoes were initially exposed to optimum PL dose (31.5 J/ cm(2)) and then washed 2 min in LAPEN sanitizer whereas for LAPEN-PL combination, tomatoes were initially immersed 2 min in LAPEN prior to PL treatment. Treatment of PL-LAPEN demonstrated a strong synergistic inactivation as no Salmonella survivor were detectable after treatment indicating greater than 5 log reduction, whereas LAPEN-PL combination revealed a compound inactivation providing 4.5 logs reduction of the pathogen. The PL-LAPEN treatment not only reduced native microbiota of tomato but also hindered their growth while in storage for three weeks. The firmness and visual appearance quality of tomato were not significantly influenced due to PL-LAPEN combination treatment until day 21, when the texture of treated tomato was significantly influenced. Overall, the results reveal that PL-LAPEN combination treatment can be implemented as a novel approach to enhance microbial safety and quality of cherry tomato.