Fish is one of the most sensitive products in regard to external environmental conditions, and any slight change can affect their storage conditions. For that reason, all steps taken from the moment we buy it until it is cooked are very important to ensure that the product doesn’t get degraded and retains all its properties intact.
The first thing to consider is the form in which we have acquired the fish. If we bought it fresh, we must clean it before storage, remove its scales and guts and wash its abdominal cavity. To prevent any liquid from leaking and contaminating other food products, you should always store it in an airtight container for it to properly dry. If our intention is to eat the fish in the short term, we can keep it in the fridge (where both white and blue fish can last two or three days). If that’s not the case, it is best to freeze it. In the freezer, blue fish will last between two and three months, while white fish can reach eight months. We also need to have always in mind -especially those lovers of raw or undercooked fish- possible contaminations by parasites, such as the ubiquitous anisakis, which can be harmful to humans when fish is raw, smoked or marinated. Deep freezing (-20 °C) for 48 hours prior to cooking is the best way to end these threats. If we choose simple freezing -or have already bought the fish frozen- the most important thing will be to ensure at all times that the cold chain is not broken; that is, making sure the product does not defrost nor suffer significant changes in storage temperature for too long. In that case, its accelerated degradation is simply inevitable: frost rapidly appears and fish begins to lose water, with the consequent loss of quality and taste. Before consuming, it is also very important the fact that thawing process takes place in the refrigerator and not at room temperature or by any external fluids.
Some much less common techniques at home include cured fish (drying, salting, mojama and smoking, which can be both cold or hot). All these procedures are typically used by professionals who perfectly know how to apply salting and drying operations, the appropriate amounts in each case and the use of thermal alteration, if necessary. Along with these we can find marinade, which consists of applying salt and vinegar on fish conservation, thereby increasing its acidity while water content is reduced and the reproductive capacity of many pathogens, inhibited. Marinade can be cold or hot, and in the first of the two methods (as is the case of the famous anchovies in vinegar) it is always advisable to previously freeze the fresh fish before being subjected to this process, as certain microorganisms -such as the aforementioned anisakis- can resist the action of vinegar for several months.
Finally, we can refer to canned and semipreserved fish, especially frequent when talking about seafood. In these cases, product has been subjected to high temperatures that ensure the elimination of all possible germs. This also allows the preservation of all products in good conditions for a long period of time and, although it is not necessary to keep a cold storage, the advice is to always keep them free of moisture and extreme temperatures. Meanwhile, semipreservation processes are applied in some canned fish, such as anchovies and mackerel. Kept in constant cooling, this method allows a perfect conservation for a long period of time.