Antimicrobial Blue Light (aBL) as a potential tool to reduce bacterial spoilage in the fishery chain

Along the fishery chain, a high amount of fish is lost for the activity of spoilage microorganisms originating from the environment, human handling and fish themselves. Different techniques are conventionally used to reduce the growth of bacteria: from cold temperature and icing to high concentration of salts, from drying to natural antimicrobial compounds. In this study, the antimicrobial Blue Light (aBL) was considered as an innovative tool. In particular, the irradiation with light at 410 nm inhibited the growth of most bacteria isolated from skin samples of anchovies and sardines chosen for their worldwide commercial importance. Bacterial strains showed a different sensitivity to light treatment: the ones isolated from anchovy were more sensitive than those from sardine. Investigations were performed on Aeromonas bestiarum, an emerging foodborne pathogen. Upon irra- diation with light at 410 nm (200 J/cm2), a statistically significant decrease of 3 log units was observed. The same fluence rate successfully inhibited the biofilm formation of A. bestiarum, and disrupted 50 % of the adherent biomass of a 24-h old biofilm. The irradiation of Staphyococcus vitulinus compromised its viability and the associated proteolytic activity known to contribute to meat spoilage. In vivo experiments showed that aBL caused a remarkable decrease (at least 50 %) of viable counts of bacteria from anchovy and sardine skin samples conserved at 4 ◦C for one day. In conclusion, these results support the potential use of blue light in reducing the growth of skin microorganisms potentially responsible for loss of food safety, quality and decrease of storage life.