Freshness assessment of European hake (Merluccius merluccius), chub mackerel (Scomber japonicus), horse mackerel (Trachurus spp.). A practical guide.

In the last few years Italian consumers have been showing a growing interest in seafood. This is mostly down to two factors: firstly, a few scandals hitting the food industry, which raised widespread concerns about the healthiness of meat, and secondly, the emergence of in-depth studies highlighting the nutritional importance of fish, molluscs, and crustaceans. They are generally regarded as excellent sources of various minerals, fat- and water-soluble vitamins, and high-quality proteins. In fact they are now seen as valuable alternatives to other typical high-protein foods such as meat, eggs, and cheese. A distinctive feature of fish, though – especially seafish – is its lipidic components, high in polyunsaturated fatty acids (PUFAs) of the n-3 (or ω-3) family. Such fatty acids are capable of preventing various cardiovascular pathologies, especially in those who eat quite frequently even small amounts of fish (30 g per day or two 100-g servings per week). Yet, for all its indisputable nutritional properties, seafood also has a critical feature: it is highly perishable. In fact, when it comes to fish, it is the so-called freshness quality which raises the most concerns, whether you are a consumer, a restaurateur or a wholesaler. The freshness of seafood can be evaluated by chemical, physical, microbiological or sensorial methods. However, the first three approaches, apparently more repeatable and reproducible, need to be validated through sensory evaluation. In other words, when it comes to assessing certain product qualities, it is our senses we have to rely on, just like the average customer does. This is why sensory analysis has always been regarded – and is still regarded – as the primary way to evaluate seafood freshness. For quite some time now the European Union (EU) has adopted an official method for the sensory evaluation of fish freshness. Its enforcement, though, has been far from straightforward. This has led some researchers from North Europe to create an alternative method, named Quality Index Method or QIM. These two different approaches will be discussed throughout this practical guide, which was born out of an agreement between Manfredonia consortium for the wholesale fish market (Consorzio per il Mercato Ittico all'Ingrosso, Manfredonia, Apulia region, South Italy) and the Department of Veterinary Morphophysiology and Animal Production at Bologna University. The agreement dealt with the nutritional, technological, and sensory profiling of three species quite commonly caught in the Gulf of Manfredonia: European hake (Merluccius merluccius), chub mackerel (Scomber japonicus), and horse mackerel (Trachurus spp.). This practical guide was prepared with various goals in mind: a. to show how the two sensory methods of freshness evaluation, so different in their approaches, should be applied; b. to produce a photographic guide about the freshness indicators of these three species which can be used for both the training of assessors and during the normal use of whichever scheme (EU or QIM) one might opt for. The aim is to improve consistency of judgement among the assessors themselves by improving both repeatability and reproducibility of either approaches, thus enhancing their credibility; c. to convince potential users that sensory approach, with all its subtleties, is far from trivial and that, if used correctly, can be both practical and effective.