The fate of Salmonella enterica and Listeria monocytogenes in the pulp of eight native Brazilian and exotic fruits

Abstract

Despite the wide variety of native and exotic fruits in Brazil, there is limited understanding of their ability to support pathogens during storage. This study aimed to evaluate the behavior of Salmonella enterica and Listeria monocytogenes inoculated into the pulp of eight fruits native and exotic to Brazil: Jenipapo (Genipa americana L.), Umbu (Spondias tuberosa Arruda), Mana ´ (Solanum sessiliflorum), Caja-manga ´ (Spondias dulcis), Physalis (Physalis angulata L.), Feijoa (Acca sellowiana), Cupuaçu (Theobroma grandiflorum) (average pH < 3.3) and in a low acidy fruit: Abiu (Pouteria caimito) (pH 6.11). The pathogens were inoculated into the different fruits and stored at 10, 20, 30 and 37 ◦C for up to 12 h and 6 days, respectively. Among the fruits evaluated, Abiu was the only one that allowed Salmonella growth, showing higher δ-values at 20 and 30 ◦C (5.6 log CFU/g for both temperatures). For Physalis and Feijoa, there was a small reduction in the pathogen concentration (<1 log-cycle), mainly at 10 and 20 ◦C, indicating its ability to remain in the matrices. For the other fruits, notable negative δ-values were ob tained, indicating a tendency towards microbial inactivation. The survival potential was significantly affected by temperature in Abiu, Mana´, Cupuaçu, and Caja-manga ´ (p < 0.05). The same phenomena regarding δ-value were observed for L. monocytogenes population, with the greatest survival potential observed at 20 ◦C in Abiu (3.3 log CFU/g). Regarding the exponential growth rates in Abiu, the highest values were observed at 30 and 37 ◦C, both for Salmonella (4.6 and 4.9 log (CFU/g)/day, respectively) and for L. monocytogenes (2.8 and 2.7 log (CFU/g)/ day, respectively), with no significant difference between both temperatures. Regarding microbial inactivation, L. monocytogenes showed greater resistance than Salmonella in practically all matrices. Jenipapo and Umbu were the pulps that, in general, had the greatest effect on reducing the population of pathogens. Furthermore, the increase in storage temperature seems to favor the increase on inactivation rates. In conclusion, Salmonella and L. monocytogenes can grow only in Abiu pulp, although they can survive in some acidic tropical fruits kept at refrigeration and abusive temperatures.