The Influence of Salting Procedures on the Characteristics of Heavy Salted Cod

The production of heavy salted cod (bacalao) has changed from being a single-step process salting to a multistep
procedure. The aim of this study was to gain a deeper understanding of water retention and yields of heavy
salted cod as influenced by salting procedures. The effects of different pre-salting methods (injection and
brining, brining only, and pickling) were compared to a single kench salting step. The products were evaluated at
different stages of the process: after pre-salting, dry salting, storage and rehydration, with regard to changes in
yields, chemical content and salt-induced changes in muscle proteins and microstructure.
Injection was significantly different from other methods in increasing weight yields through brining, dry salting
and rehydration. Salt concentrations of the brine did not influence the weight yields of dry-salted and rehydrated
products. However, salt concentrations >20% had negative effects on the colour and commercial quality of the
salted products. Addition of phosphates increased weight yield of salted but not of rehydrated products. Effects
on quality varied between trials; both negative and positive effects were observed.
Strong salting-out effects on proteins were seen due to high salt contents in the salted products regardless of the
procedures applied. The effects of salting procedures on yields and quality of heavy salted cod products were
related to the pathway of solubilisation, denaturation and aggregation of proteins in the muscle. Myosin was less
aggregated when injection was applied during pre-salting. A greater degree of protein aggregation correlated
with higher initial salt concentrations and dehydration during the first days of salting, which was obtained with
brining, pickling and kench salting. In addition, these methods resulted in stronger enzymatic degradation of
proteins, shown as an increase in lower molecular weight subunits.
The connective tissue in the muscle was believed to play an important role in water retention of the muscle.
Microstructural analysis of the dry-salted fillets showed that the intercellular spaces in injected and brined fillets
were increased compared to only brining. However, the cross-sectional area of the fish fibres was similar in both
groups.
Based on this, the main reason for higher weight yields of injected products after salting and rehydration were
believed to result from irreversible effects on the connective tissue in the muscle and better retention of myosin
structure, thereby better water-holding. The drawback of the wet-salting methods (brining and injection) was that
the yield of nitrogenous compounds was lower for injected and brine-salted fillets. However, the main changes
were due to higher losses of non-protein nitrogen, which is more likely to influence the organoleptic properties
of the products than the weight yields.