Dry-ageing of fish: microbiological and physico-chemical assessment of wild-caught greater amberjack (Seriola dumerili) in a restaurant setting

Dry-ageing is increasingly applied to fish in the restaurant sector, but information on its safety in wild-caught marine species is lacking. This study evaluated the microbiological and physico-chemical evolution of dry-aged greater amberjack (Seriola dumerili) under controlled restaurant conditions. Two batches of wild-caught fish were dry-aged at 1 ± 0.5 °C and 65% relative humidity for up to 21 days and sampled at 0, 14 and 21 days. Microbiological analyses included microbial groups commonly used to assess hygienic and safety criteria, including Listeria monocytogenes, while physico-chemical parameters comprised water activity (aw), pH, muscle color, lipid oxidation, total volatile basic nitrogen (TVBN), and volatile and biogenic amines. Microbial loads differed among tissues and over time. Skin samples displayed higher microbial loads, particularly at early stages. While dorsal muscle generally showed low and stable microbial levels, ventral muscle exhibited heterogeneous trends. Coagulase-positive staphylococci were always below the limit of detection and Listeria monocytogenes was never detected. Aw, pH and lipid oxidation showed limited changes, while TVBN increased over time, exceeding reference limits in all samples by day 21, mainly due to ammonia and dimethylamine accumulation. Biogenic amines, including histamine, remained within acceptable levels. By providing preliminary data, this study contributes to the identification of critical parameters and supports the development of future risk assessment and food safety management strategies for dry-aged fish.