Discrimination between Fresh and Frozen-Thawed Fish Involved in Food Safety and Fraud Protection

• Published in: Foods
• Main Authors: Luca Maria Chiesa, Radmila Pavlovic, Maria Nobile, Federica Di Cesare, Renato Malandra, Davide Pessina, Sara Panseri
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: food safety; freezing; thawing; high resolution mass spectrometry; Atlantic salmon; bullet tuna; Chemical technology; TP1-1185; Salmo salar
• Online Access: https://doi.org/10.3390/foods9121896; https://doaj.org/article/cab40a5d8433459a9d15aace335b2875

This study aims to discriminate fresh fish from frozen/thawed by identification of the key metabolites that are altered during the freezing/thawing processing. Atlantic salmon ( Salmo salar) and bullet tuna ( Auxis rochei ) were selected as they are representative of broad consumption, and susceptible to pathogen contamination. Atlantic salmon samples were subjected to the following regimes: −20 °C (24h) and −35 °C (15 h) freezing, then thawed respectively in the blast chiller and in the cold room and analyzed immediately or after 10 days; (2) bullet tuna samples were frozen at −18 °C and thawed after 15, 30 and 90 days. High resolution mass spectrometry based on untargeted metabolomic analyses and statistical data treatment confirmed significant variations in the quantity of certain metabolites: the amount of l -phenylalanine in salmon increased immediately after thawing while that of anserine decreased. The concentration of l -arginine and its metabolites was altered at the 10th day after thawing rendering them promising markers of salmon freezing/thawing. As regards bullet tuna, compounds resulting from lipid degradation ( l -α-Glyceryl-phosphoryl-choline and N-methyl-ethanolamine phosphate) increased notably during the storage period. This approach could be used to reveal common fraudulent incidents such as deliberate replacement of fresh fish with frozen/thawed, with food safety risks as the primary implication.