Evaluation of the effects of root decontamination of Salmonella spp. using lactic acid bacteria and quality attributes of living cilantro grown (Coriandrum sativum) using the nutrient film technique (NFT)

Between 2000 and 2020, the CDC's National Outbreak Reporting System recorded 43 cilantro-related outbreaks, leading to 970 illnesses and 75 hospitalizations, with no fatalities. Contaminated cilantro has been linked to pathogens like Salmonella and Cyclospora. The Nutrient Film Technique (NFT), which uses water recirculation and exposes only plant roots to nutrient solutions, is ideal for small-rooted plants like herbs but creates conditions favorable for foodborne pathogens like Salmonella. Additionally, contamination can occur in potted plants due to their roots being in constant contact with contaminated growing media or water. This poses a risk as the roots are a direct pathway for pathogens to enter the plant, potentially affecting its edible parts and increasing the risk of foodborne illness. A comprehensive study was conducted to assess the efficacy of cilantro root decontamination of Salmonella using lactic acid bacteria treatments and evaluate its impact on the quality properties of the cilantro plants. Living Cilantro plants (roots attached) were grown following the market standards in NFT units for 21 days of cultivation before evaluation. On day 22, living cilantro plants (roots attached) were inoculated by immersion in a 500 mL Salmonella inoculum containing 4 Log CFU/mL and subsequently placed for 2 hours in a biosafety cabinet to facilitate bacterial adhesion. Three treatments were evaluated in this study: LAB treatments, Lactiguard™, Enterococcus faecium L-20B, and Probicon L28, which were reactivated following the manufacturers' guidelines. Probiotic treatments were prepared at a concentration of 9 Log CFU/mL based on prior in vitro results. A dip wash process treated cilantro roots with LAB solutions for 5 minutes after contamination. Each plant was packaged in compostable polylactic acid (PLA) containers with moisture-absorbing pads and stored at 10º C for 14 days. Samples were collected on days 0, 3, 7, and 14 for bacterial analysis using MRS and XLD agar with TSA overlay containing nalidixic acid (50 µg/mL). Quality assessments included leaf chlorophyll content and plant weight. Statistical analyses indicated that time and treatment affected LAB and Salmonella counts (P > 0.05). Salmonella levels significantly decreased with LAB treatments; by day 3, Lactiguard™ eradicated Salmonella, while Enterococcus faecium showed none after day 7. Probicon L28 reduced Salmonella but required enrichment for verification. Salmonella persisted longer on absorbent pads, while Lactiguard™ completely suppressed it by day 7. Conversely, Enterococcus faecium allowed for Salmonella regrowth by day 7, and Probicon L28 required enrichment for detection throughout the study. By day 14, lactic acid bacteria (LAB) count on cilantro roots and absorbent pads decreased by about 2 log units across treatments. Lactiguard™ consistently maintained the highest LAB counts, despite Probicon L28 showing better initial stability on absorbent pads. Probiotic treatments did not negatively impact post-harvest quality, as indicated by stable chlorophyll levels and minimal weight loss, supporting the use of these bacteria as effective post-harvest interventions.