Biopreservation of fresh-cut melon using the strain Pseudomonas graminis CPA-7

The use of biopreservation is a promising technique to ensure microbial safety of fresh-cut produce. The objective of this work was to test the effectiveness of the strain CPA-7 of Pseudomonas graminis against a cocktail of Salmonella spp. and Listeria monocytogenes on fresh-cut melon, and evaluate its effect on its quality during shelf-life when tested in conditions simulating commercial application. Fresh-cut melon was artificially inoculated with Salmonella spp. and L. monocytogenes and with or without the biopreservative strain at different concentrations and stored at 20, 10 and 5 degrees C. Moreover, the effect of the strain was tested in conditions simulating commercial application. Fresh-cut melon was packaged using passive modified atmosphere (MAP) and AIR conditions and stored at 5 and 10 degrees C. Quality of fresh-cut melon was evaluated in CPA-7 treated and untreated samples. At laboratory scale trials, P. graminis reduced Salmonella and L monocytogenes growth on fresh-cut melon stored at 5, 10 and 20 degrees C. Effectiveness depended on their concentration and on storage temperature. At low pathogen concentration and 20 degrees C, L. monocytogenes growth was reduced between 2.1 and 5.3 log cfu g(-1) units after 2 days of storage and Salmonella growth between 2.0 and 7.3 log cfu g(-1) depending on CPA-7 dose. At 10 degrees C, similar reductions of pathogens were observed after 5 days of storage. In studies simulating commercial conditions, packaging atmosphere and temperature influenced P. graminis effectiveness, with better results in samples packaged under AIR conditions and 10 degrees C. Reduction of pathogen growth was <1-log unit in fresh-cut melon stored in MAP whilst it was >4-log units in AIR. Soluble solids content, titratable acidity, pH and firmness of fresh-cut melon were not significantly different in CPA-7 treated and untreated (control) melon. In general, lightness, chroma and hue values of fresh-cut melon stored in AIR decreased faster in CPA-7 samples than on control ones. At 5 degrees C, CPA-7 treated melon was visually scored lower than untreated melon. P. graminis has demonstrated promising results at 10 degrees C, which is a temperature more compromised for safety. Nevertheless more detailed studies on the modified atmosphere are required because AIR packaging is not recommended due to the rapid loss of quality. (C) 2014 Elsevier B.V. All rights reserved.