Biometric, rheological, and nutritional characterisation of soft-shell Mediterranean green crabs (Carcinus aestuarii)

Soft-shell crabs harvested immediately after moulting represent a delicacy among seafood products. Among several species, the soft-shell crabs derived from Mediterranean green crabs (Carcinus aestuarii), known as ‘moeca’ (plur. moeche), stand as culturally and economically valuable products in the Northern Adriatic. Despite their cultural significance, comprehensive information on their bio-metric, rheological, and chemical traits is lacking. This study provides the first integrated characterisation of the quality of moeca, assessing site- and sex-specific variation and comparing them with hard-shell crabs. Two sites, North and South, of the Lagoon of Venice were selected for sampling. A total of 160 soft-shell crabs from the North site and 80 from the South site, along with 40 hard-shell crabs per site, were collected in batches of about 1.2 kg, transported to the laboratory, and immediately analysed for biometry, texture profile analysis, and colour. In addition, whole soft-shell crabs were analysed for proximate composition, mineral, fatty acid, and amino acid profiles. Biometric measurements indicated larger individuals in the southern site, while all crabs were of marketable size (32.6 ± 5.6 mm carapace width). Texture profile analysis revealed softer, more cohesive, and more elastic carapaces in moeche than hard-shell crabs, with significant differences between sites. Site-and sex-related differences were found in carapace brightness and chromatic indices. Modest but significant site-related variations were recorded in protein, lipid, ash, chitin, mineral, and fatty acid profiles. Overall, our findings provide a detailed baseline dataset for the characterisation of moeche,supporting product valorisation strategies such as labelling policies.