Modeling Behavior of Salmonella spp. and Listeria monocytogenes in Raw and Processed Vegetables

Given the persistent occurrence of foodborne illnesses linked to both raw and processed vegetables, understanding microbial behavior in these foods under distribution conditions is crucial. This study aimed to develop predictive growth models for <i>Salmonella</i> spp. and <i>Listeria monocytogenes</i> in raw (mung bean sprouts, onion, and cabbage) and processed vegetables (shredded cabbage salad, cabbage and onion juices) at various temperatures, ranging from 4 to 36 °C. Growth models were constructed and validated using isolated strains of <i>Salmonella</i> spp. (<i>S</i>. Bareilly, <i>S.</i> Enteritidis, <i>S</i>. Typhimurium) and <i>L. monocytogenes</i> (serotypes 1/2a and 1/2b) from diverse food sources. The minimum growth temperatures for <i>Salmonella</i> varied among different vegetable matrices: 8 °C for mung bean sprouts, 9 °C for both onion and cabbage, and 10 °C for ready-to-eat (RTE) shredded cabbage salad. Both pathogens grew in cabbage juice at temperatures above 17 °C, while neither demonstrated growth in onion juice, even at 36 °C. Notably, <i>Salmonella</i> spp. exhibited faster growth than <i>L. monocytogenes</i> in all tested samples. At 8 °C, the lag time (LT) and specific growth rate (SGR) for <i>Salmonella</i> spp. in mung bean sprouts were approximately tenfold longer and threefold slower, respectively, compared to those at 10 °C. A decrease in refrigerator storage temperature by 1 or 2 degrees significantly prevented the growth of <i>Salmonella</i> in raw vegetables. These findings offer valuable insights into assessing the risk of foodborne illness associated with the consumption of raw and processed vegetables and inform management strategies in mitigating these risks.