Shelf-Life Evaluation of Ready-to-Eat Baby Leaf Salads.

Ready-to-eat (RTE) baby-leaf salads (Lactuca sativa L.) are increasingly prevalent in the market due to the possibility of consumption without additional processing. Although these salads are stored under refrigerated conditions, they remain highly perishable and may be associated with foodborne illness, as they can be contaminated with pathogens such as Salmonella spp., Listeria monocytogenes, and Escherichia coli. Therefore, shelf-life evaluation is essential to ensure their microbiological safety and overall quality during storage. This study was conducted to evaluate the shelf life of RTE baby-leaf salads produced following two different washing procedures and stored at 7 °C. Ten production batches were analyzed, with three sampling units per batch at five time points: production day (T0), and after 3, 7, 10, and 11 days of storage. Microbiological and molecular analyses using real-time PCR were performed in accordance with ISO standards or alternative validated methods to monitor spoilage and hygiene indicator microorganisms, including mesophilic microorganisms, coliforms, yeasts, molds, and β-glucuronidase–positive Escherichia coli. Pathogenic microorganisms (Salmonella spp., Listeria monocytogenes, and STEC E. coli) were monitored only at T0, as spoilage organisms are the primary contributors to microbial growth during refrigerated storage. The results showed significant differences among batches for mesophilic microorganisms, coliforms, yeasts, and molds, with mean values ranging from 4.94 to 7.60 log CFU/g for mesophiles, 3.52 to 5.45 log CFU/g for coliforms, 2.13 to 4.42 log CFU/g for yeasts, and 2.88 to 3.88 log CFU/g for molds. At T0, batch variability influenced mesophiles and coliforms, while washing treatments affected mesophiles overall and yeasts within individual batches. Storage time significantly influenced the growth of mesophiles, coliforms, and yeasts, whereas washing treatments did not. Towards the end of shelf life (T7, T10, and T11), microbial loads increased for all batches, with mesophiles and coliforms showing the most pronounced growth in conventionally washed samples, and coliforms and yeasts in combined washed samples. No pathogenic microorganisms were detected in any of the ready-to-eat baby-leaf salad samples. These results highlight the strong influence of storage time and batch variability on the microbiological quality of ready-to-eat baby-leaf salads, while washing treatments had only a minor impact. This information can be useful for designing strategies to maintain the microbiological safety and quality of ready-to-eat salads.