Omar Peñarubia, 29 June 2021

Salting, or salt curing, is one of the oldest methods of fish preservation used by the Romans to produce the famous salt cod, or bacalao. Salted fish has endured because it can be stored for long periods of time and does not necessarily require refrigerated storage. And, when desalted and prepared well, it can taste just like fresh fish!

So what is salting? Basically, salt (food-grade) is added to fish in order to lower what is called the Water Activity (Aw). Fish flesh contains 75-80% water (fatty fish, 60-65 %), and during salting some of this water is removed and replaced by salt. A concentration of between 6–10 % salt in the fish tissue together with the drying effect due to loss of water will prevent the growth of most spoilage bacteria, and hence preventing a loss.

Fish are typically brined (a mixture of salt and water), wet-salted, or dry-salted. It is important to remember that the salting process will have an impact on the quality of the final product, thus it should be carried out under strict hygienic conditions (GHP) to prevent food safety issues such as the development of C. botulinum in vacuum-packed products. Furthermore, maintaining the temperature lower than 8 °C (below 4 °C for fish that may form scombrotoxin) to avoid the formation of histamine in some species is recommended.

Salted fish and fish products should be sound and wholesome, well prepared and packaged in a way that will protect the product from contamination and yet keep the product attractive and safe to eat. In order to maintain the quality of fish, it is important to adopt quick, careful and efficient handling procedures, and to always process top quality fresh fish. The Codex Alimentarius Code of Practice for Fish and Fishery Products is a reference point for good practice and provides guidance on processing of salted and dried salted fish.

Although salted fish can be a robust product, it can be susceptible to loss in quality due to colour change or discolouration brought about by lipid (fat) oxidation and the growth of salt tolerant (halophilic) bacteria and moulds.

The type and quality of salt is hugely important. Salt used should be food grade and not subsequently contaminated with dirt, oil, bilge or other extraneous materials. Halophilic bacteria and moulds can be found in solar salt. Previously used or contaminated salt must not be used.

Mine salt and solar salt of marine origin contain calcium sulphate, magnesium sulphate and chloride while vacuum-processed and refined salt is almost pure sodium chloride. Too much calcium in salt may reduce the rate of salt penetration to the extent that spoilage may occur. If present at too high a concentration, magnesium salts will give rise to unpleasant bitter flavours and may cause spoilage, and thus a loss, during the salting operation.

Additionally, the size of salt crystals matters. Using very fine salt granules could result in the formation of salt clusters, which is not favourable for ensuring the uniform distribution of salt on the fish. On the other hand, very coarse salt granule could result in damage to the fish flesh during salting and may prolong the salting time.

Salting fish has been around for a long time and is probably here to stay. Yet, to produce good quality salted fish that can sell for a high price it is crucial that good salting practice is applied efficiently and safely in order to reduce the risk of loss and ultimately add value to the final product.

Find more information and resources on fish salting here.