64 MARCH 2022 • WORLD AQUACULTURE • WWW.WA S .ORG dorsal and pectoral fins removed prior to salting (Anenias et al. 1978, Eong and Hui 2010). As most fish are very small, viscera are seldom removed to preserve the form and integrity of the fish (Wernstedt and Spencer 1968, Doe 1998). Salt is introduced through dry salting or brining. Dry salting involves the use of salt and a container, where fish are rubbed with salt prior to incubation for five days (Doe 1998, PNS 2006b). With the high concentration of salt outside the fish, innate water in the flesh is drawn out due to osmosis and swelling of proteins. As proteins swell to their limit, the flesh starts to shrink, thus pushing out innate and absorbed water to the environment (Beatty and Fougere 1957, Boon et al. 2010, Turan and Erkoyuncu 2012). The salt is then left in the proteins as it begins to harden, thus causing the flesh to toughen. The high concentration of salt also ensures no unbound water is available, therefore effectively decreasing the water activity of the product (Boon et al. 2010, Rahman 2009, Turan and Erkoyuncu 2012). A decrease in water activity inhibits growth and proliferation of microorganisms (Bekhit 2017, Boon et al. 2010). Moreover, a high salt concentration causes osmotic shock to microorganisms that forces water out of the microbial cell, leading to cell growth retardation or even death (Boon et al. 2010, Wood 2015). Salting helps in the preservation of fish and also introduces flavor and alters the texture of the flesh, making the fish saltier and tougher (Gudjónsdóttir et al. 2015, Bekhit 2017). Brining also uses the same mechanism although, instead of rubbing salt onto the flesh, fish are immersed in a high-concentration salt solution (Beatty and Fougere 1957, Turan and Erkoyuncu 2012, Bekhit 2017). After salting, fish are washed to remove excess salt. Salted fish are then placed on drying racks, using the sun as the main source of heat. Drying is a method to remove water from a food product through artificial or natural means. Sun-drying is a traditional method that is more convenient and economical for fish processors; it merely requires setting up racks and drying areas that are easily accessible. It is the most popular method of drying in the country as it is easily accessible to farmers and small-scale businesses. This type of drying method depends on the heat generated by the sun and on water evaporation. Sun-drying requires a long time, especially to achieve the desired texture and hardness. It is also more difficult to control due to varying weather conditions and environmental factors, such as humidity, temperature and presence of other living organisms (Boziaris 2013, Gabriel and Alano-Budiao 2015). These factors result in inconsistent quality of dried fish as contamination can occur. Although unconventional, other countries have employed the use of industrial-scale ovens to have more control over the temperature and time exposure to heat (Arvanitoyannis et al. 2012). Some even try to innovate the process by introducing air dryers with heat sensors (Macabutas et al. 2018). Salting and drying of fish are often employed together but fish can also be dried without salting (Arvanitoyannis et al. 2012, Boziaris 2013). Unsalted, dried fish has a shorter shelf-life and less desirable textural properties (Gudjónsdóttir et al. 2015). Salted, non-dried fish is often consumed immediately as it is not suitable for long-term storage. Dried, salted fish products have a moisture content between 18 and 42 percent (Rasul et al. 2018, Zhelyazkov and Stratev 2018). Different drying methods and fish type can greatly affect the moisture content of dried, salted fish products (Rasul et al. 2018, Zhelyazkov and Stratev 2018). The water activity of dried, salted fish ranges from 0.75 to 0.81, which also varies depending on the drying and salting methods used (Fetriyuna et al. 2017, Zhelyazkov and Stratev 2018). The Philippines has a variety of dried, salted fishery products sourced from the wild or from aquaculture. Dried and/or salted mussel (lower left), mackerel (upper left), anchovy (center), slipmouth ponyfish (upper right), and rabbitfish or siganid (lower right) cost between US$ 0.75 to 1.25 per 100 g (Photo: J.A. Ragaza). Dried, salted groupers are considered premium products and usually sold in specialty stores. A 250-g pack costs around US$ 5 to 6 (Photo: J.A. Ragaza).
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