Evaluation of the Level of Toxic Contaminants and Essential Molecules in the Context of the Re-Use of Tuna Fishery Industry by-Products

The tuna fish processing industry produces more than 50% of waste and by-products (scales, head, viscera, etc.) that are usually discarded or used to produce low added value products such as fish meals. However, these waste materials still contain molecules essential for the human diet, such as essential metals, vitamins, omega-3 fatty acids, amino acids, and proteins of high nutritional value. The re-use of such wastes for the production of dietary supplements for human consumption would perfectly fit with the concept of Blue Economy, defined as the sustainable use of ocean resources for economic growth, improved livelihoods, and jobs while preserving the health of the ocean ecosystem. Moreover, waste product revenue will be a key factor in maintaining long-term profitability of industrial food processing. In this work, the yellowfin tuna ( Thunnus albacares ) was used as a model for fish processing by-products, as it is a large epipelagic species widely distributed in the tropical and subtropical waters of the major oceans. The determination of heavy metals and histamine is an essential control point for the re-utilization of the wastes. Then, they must be monitored in all the processes leading to the formulation of new high-quality products. Inductively coupled plasma–mass spectrometry and a fast gas chromatographic–mass spectrometry methods were validated and applied for the determination of metals and histamine and amino acids, respectively. In particular, both essential and heavy metals and histamine and amino acids were quantified in tuna fish by-products. The presence of essential metals and essential amino acids in the analyzed samples represents the strength point of the proposed model, which aims to valorize by-products and reduce the disposal of wastes.