MICROBIOLOGICAL QUALITY AND SAFETY OF FARMED SEAWEED ALARIA ESCULENTA AND SALMON SALMO SALAR CO-CULTURED IN AN INTEGRATED MULTITROPHIC AQUACULTURE SYSTEM

Although advantages and limitations of Integrated Multi-trophic Aquaculture (IMTA) have been widely reported, few studies have focused on potential effects of IMTA on the microbiological quality and safety of the end products. In the current study, the spoilage potential as well as the presence of pathogenic bacteria in two different species (salmon Salmo salar and seaweed Alaria esculenta) cultured in IMTA system were investigated. In addition, several nutritional parameters were evaluated so as to provide a preliminary view about the nutritional quality of such products. Alaria esculenta and Atlantic salmon were co-cultivated at a pilot scale IMTA site, Lehanagh Pool, operated by the Marine Institute in the west coast of Ireland. Both species were harvested in May 2020. The collected samples were subsequently packaged and sent to the Laboratory of Food Microbiology and Biotechnology (Agricultural University of Athens, Greece) for microbial testing. The received samples were placed in polystyrene trays and stored at different temperatures (0, 5, 10, 15^oC for the seaweed, and 0 and 4^oC for the salmon) for specific time intervals. Microbiological analysis was performed on the day of their arrival at the lab and at certain days of storage, for the estimation of Total Viable Counts (TVC), Pseudomonas spp., Lactic acid bacteria, Enterobacteriaceae, Bacillus spp., B. thermosphacta, Vibrio spp., Aeromonas spp., yeast and moulds, E. coli, Salmonella, Listeria monocytogenes and Staphylococcus aureus. Nutritional analyses, including the determination of protein, fat, carbohydrate, ash and moisture content, were performed on the day the samples arrived at the lab. Products were of acceptable microbial quality (TVC < 7.0 log CFU/g) and safe for human consumption for up to 12 days stored at 0^oC and 8 days stored at 4^oC. The time period for seaweed samples was 8 and 4 days for 0 and 5^oC, respectively, while initial microbial load was in accordance with findings reported by Blikra et al. (2019). It should be noted that bacteria of Enterobacteriaceae family which are considered as hygiene indicator, were at low levels - even below enumeration limit - in both species, while all the examined pathogenic bacteria were absent both at the beginning and at the end of storage. Although further research is intended regarding quality and safety of IMTA products, for example, the detection of antibiotic resistant microbial strains, these preliminary findings provide significant information about the overall microbiological quality of IMTA products. As far as the nutritional quality of the tested samples is concerned, specific nutritional parameters (such as protein, fat and carbohydrate content) were found to be similar to reference values for the same species (non-IMTA).