Microbiological hygiene and food safety assessment of urban aquaponic farming

Aquaponic production presents a promising approach in developing sustainable (urban) food systems, through combined production of plants and aquatic organisms for food. A commercial aquaponic farm was subjected to a longitudinal microbiological assessment of hygiene and food safety. Foodborne pathogenic bacteria (Salmonella spp., and Listeria monocytogenes), indicator bacteria (generic E. coli, coliforms, and Enterobacteriaceae) and total plate counts were determined during two distinct two-month production periods, focused on basil production from seed to mature plant and all water streams composing the irrigation water. The results indicated no direct food safety concerns to consumers, with neither Salmonella spp., nor Listeria monocytogenes detected on the ready-to-market basil leaves. The soilless substrate and irrigation water were identified as major risk factors for introducing and spreading foodborne pathogenic bacteria within the aquaponic environment. Overall, E. coli was present (LOD 1 CFU/100 mL or 10 CFU/g) in 21.1 % of samples and Salmonella spp. was detected in 8 out of 94 analyses. Generic E. coli was not a suitable marker for Salmonella spp. presence in irrigation water within the aquaponic farm. Strong correlations were found between Enterobacteriaceae and coliforms in water samples, however, elevated levels were not linked to positive Salmonella spp. detection. To mitigate microbiological food safety risks in aquaponics, the use of fit-for-purpose water, establishing a water quality monitoring plan, implementing effective UV treatment and applying appropriate cleaning and disinfection protocols are recommended. The implementation of tailored good agricultural practices (GAP) is key to ensure safe food production within aquaponic farming.