Labelling assessment and molecular authentication of squid-based products from two major European cities

This study provides the first assessment of labelling compliance and species authenticity of squid-based products sold in two major EU cities, Brussels and Milan. A total of 198 products were collected from supermarkets, fishmongers and the food service sector. They were analysed through label evaluation and molecular authentication using DNA barcoding (mono-species samples) and DNA metabarcoding (multi-species samples). Mislabelling was detected in 13.3% of products in Brussels and 30.2% in Milan. Substitution patterns frequently involved the replacement of high-value Mediterranean or Northeast Atlantic species with lower-priced imported taxa. When mislabelling rates were recalculated by restricting the analysis to products allowing species-level verification, comparable mislabelling frequencies were observed between the two cities (27.3% for Brussels and 26.5% for Milan). This indicates that differences between cities are largely driven by national seafood nomenclature systems, with the widespread use of umbrella commercial designations in Belgium hindering species-level verification. Statistical analyses indicated no significant association between mislabelling frequency and product category or retailer type. Overall, these results highlight transparency gaps in the squid markets analysed and support the need for harmonised labelling requirements, including mandatory species information for processed products and the food service sector.