Evaluation of maximum growth rate of Listeria monocytogenes in ready-to-eat fresh-cut papaya and melon

Listeria monocytogenes has been identified on minimally processed fruit and vegetables, and can transmit a severe foodborne disease through the consumption of ready-to-eat (RTE) fresh-cut produce, mostly if the storage conditions are incorrect, and the cold chain is not abided to. The aim of the present work was to evaluate the behaviour of L. monocytogenes in RTE fresh-cut papaya and melon, two low-acid fruits stored in temperature-abuse conditions (10 and 8°C, respectively) during the shelf-life indicated by the producer (7 d). A microbiological challenge test was performed to assess the maximum growth rate (MGR) and the duplication time (Td) of the pathogen, testing three strains separately. We also assessed the behaviour of the indigenous microflora of the fruits. Results demonstrated that papaya and melon were two favourable substrates for L. monocytogenes. The MGR was 0.044 log CFU/g/h with a Td of 6.77 h for papaya, and 0.029 log CFU/g/h with a Td of 10.24 h for melon. The storage of RTE fresh-cut papaya and melon at an abusive temperature above 8°C could encourage the growth of L. monocytogenes with a possible risk to public health.