Towards better microbial safety of fresh produce: Chlorophyllin-based photosensitization for microbial control of foodborne pathogens on cherry tomatoes.

The aim of this study is to evaluate the antimicrobial efficiency of Chlorophyllin-based photosensitization for microbial control of cherry tomatoes. Chlorophyllin-based photosensitization (1.5 × 10 M, 3 J/cm) significantly (2.4 log) reduced the population of naturally distributed surface attached various mesophilic bacteria (microbiota) on tomatoes. Moreover, the population of thermoresistant strains of food pathogens Bacillus cereus and Listeria monocytogenes inoculated on tomatoes was reduced by 1.5 log and 1.6 log respectively after this treatment. Conventional washing with water reduced the population of Listeria on tomato by 0.6 log and Bacillus by 0.8 log. In comparison, hypochlorite treatment reduced Listeria on tomatoes by 1.4 log and Bacillus by 1.6 log. The regrowth of mesophilic bacteria and thermoresistant Listeria on the surface of tomatoes after photosensitization was delayed for 28 days and 14 days respectively. Moreover, photosensitization did not induce harmful effects on main parameter of nutritional quality of tomatoes, i.e. antioxidant activity of tomatoes remained unchanged (27.5 mM Fe/kg). Eventually, this treatment did not induce visible thermal effects in fruit matrix and prolonged the shelf-life of tomatoes by 4 days. In our opinion, chlorophyllin-based photosensitization has a huge potential as alternative to not-chemical food preservation technology, saving water and energy. In addition, fast development of light emitting diodes (LED's) and light sources based on LED technologies make this treatment low cost, environmentally friendly and easy to maintain.