Preharvest Control of Salmonella enterica in Microgreens Using Natural Antimicrobials

Abstract

Microgreens are increasingly popular as nutrient-dense fresh produce but are consumed raw and lack effective postharvest kill steps, making preharvest pathogen control essential for food safety. This study evaluated the antimicrobial efficacy of two natural formulations benzyl isothiocyanate (BIT) nanoemulsion (1%, v/v) and Sporan emulsion (2%, v/v) as preharvest interventions against in microgreen production systems. Seeds of five Brassicaceae microgreen species (daikon radish, broccoli, mustard, red cabbage, and red Russian kale) were artificially inoculated with a low-level Salmonella enterica cocktail (4-5 log CFU/ml) and treated with the antimicrobial formulations prior to cultivation. Initial in vitro disk diffusion assays showed that BIT produced significantly larger inhibition zones (10.7 ± 0.4 to 13.8 ± 0.6 mm) against S. enterica and E. coli O157:H7 compared with Sporan (9.0 ± 0.4 to 10.5 ± 0.6 mm) (p < 0.05).Seed decontamination assays demonstrated that BIT reduced S. enterica populations by 1.6 log CFU/g, while Sporan achieved a 1.2 log CFU/g reduction relative to untreated controls (p < 0.05). During a 14 day cultivation period, BIT treatment resulted in significantly lower bacterial populations on plant tissues, with the highest reductions observed in red cabbage (1.21 log CFU/g) and red Russian kale (1.78 log CFU/g) between Days 7 and 14. In contrast, changes in bacterial populations within the growing medium were not significant (p > 0.05), suggesting limited persistence of antimicrobial effects in the soil environment. Both treatments maintained seed germination rates above 60% across most species and did not significantly affect yield, except for a minor reduction in daikon radish under BIT treatment. A notable observation made was that these natural antimicrobial treatments slow the germination process compared to untreated seeds. Overall, the results demonstrate that natural antimicrobial formulations, particularly BIT nanoemulsion, offer effective preharvest interventions for reducing S. enterica contamination in microgreen systems while maintaining crop quality. These findings support the integration of BIT based nano formulations into sustainable food safety management strategies for controlled-environment agriculture.