Growth potential of Escherichia coli O157:H7 on fresh-cut fruits (melon and pineapple) and vegetables (carrot and escarole) stored under different conditions

Minimally processed fruits and vegetables are ready-to-eat and do not require further treatment at home. These foods are usually stored in a modified atmosphere and should be maintained at refrigerated conditions until consumption. These fruits and vegetables can become contaminated by foodborne pathogens such as Escherichia coli O157:H7, Salmonella and Listeria monocytogenes, and it has been demonstrated that current industrial sanitising washing treatments do not guarantee the total elimination of the pathogen when present. Thus, it is very important to elucidate whether pathogens are able to grow or survive during storage at different conditions. This study was conducted to determine the effect of the type of produce (escarole, carrot, pineapple or melon), package gas composition (air or modified atmosphere) and temperature (5 or 25 degrees C) on the population dynamics of a strain of E. colt O157:H7. For vegetables, the growth in two films, which created different O-2 and CO2 concentrations, and air were compared. At 25 degrees C, growth of E. coli O157:H7 was higher in fresh-cut carrots than in endive, reaching populations between 7.0-8.4 log cfu g(-1) and 5.2-6.3 log cfu g(-1) after 3 days of storage, respectively. In fruits, E. colt O157:H7 grew well in fresh-cut melon regardless of the atmospheric conditions in the package, reaching populations of 8.5 and 8.9 log cfu g(-1) after 1 day of storage in modified atmosphere packaging (MAP) or under air conditions, respectively. No growth was observed in the fresh-cut pineapple. At 5 degrees C, E. coli 0157:H7 did not grow but survived throughout the studied period in all tested commodities. This work emphasises the importance of strict temperature control from processing to consumption, including transportation, distribution, storage and handling in supermarkets and by consumers. (C) 2012 Elsevier Ltd. All rights reserved.