Behavior of Salmonella During Preparation of a Fermented Cashew Cheese Analog

Between 2013 and 2021, there were three reported salmonellosis outbreaks in North America linked to the consumption of cashew cheese analogs that were prepared from soaked and fermented cashews. The behavior of Salmonella was evaluated during fermentation of cashews to better understand the risks associated with plant-based fermentations. Single or seven-strain rifampin-resistant Salmonella-inoculated cashews (1–2 log CFU/g) were soaked 1:1 (w/v) in sterile ultrapure water at 4 °C for 24 ± 1 h, drained, and then blended with additional water. Salmonella-inoculated or uninoculated cashews with or without added commercial Lactococcus lactis starter culture (LAB), and with LAB and NaCl (0.8% and 1.6% w/w), citric acid (0.4% w/w), or a combination of NaCl and citric acid, were held at 24 ± 1 °C for up to 72 h. The pH, aerobic plate counts (M17 agar), and Salmonella populations (CHROMagar Salmonella with 50 µg/mL of rifampin) were measured at 0, 24, 48, and 72 h in replicate experiments. When LAB was present, aerobic plate counts increased from ∼8 log CFU/g to ∼9 log CFU/g after 24 h. The pH decreased from an initial pH ∼6 to pH 4.5–5.0 at 24 h in the presence of LAB or at 48 h in the absence of LAB. The presence of LAB significantly (P < 0.0001) impacted populations of Salmonella during the fermentation. There was no significant difference in Salmonella populations between the treatments with LAB alone and the treatments with LAB in combination with added NaCl (P = 0.3484) or citric acid (P = 0.8630). After 24 h, populations of Salmonella increased by 5.3–5.5 log in the absence of LAB and by 0.5–1.7 log in the presence of LAB, with or without added NaCl. These data demonstrate the need to consider a range of control measures for safe preparation of plant-based fermented products.