E: Food Engineering & Physical Properties JFS E: Food Engineering and Physical Properties Electrodialysis Desalination of Fish Sauce: Electrodialysis Performance and Product Quality NATHAMOL CHINDAPAN,SAKAMON DEVAHASTIN, AND NAPHAPORN CHIEWCHAN ABSTRACT: Fish sauce has a unique, pleasant flavor, but contains high levels of sodium chloride, which is nowadays not desirable for health-conscious consumers. Although many researchers have attempted to solve this problem by substituting sodium with potassium in fish sauce, potassium-based products are still unsuitable for patients with kidney disease. Thus, electrodialysis (ED) desalination of fish sauce was carried out. The rate of salt removal, evo- lution of total soluble solids, and electrical conductivity of the electrodialysis-treated fish sauce were investigated. Moreover, the system performance in terms of yield, energy consumption, and current efficiency were examined. Density, viscosity, ion concentrations (that is, Na + ,K + ), total nitrogen, amino nitrogen, and color were investigated at various values of input voltage (6, 7, and 8 V) and remaining salt concentration (22%, 18%, 14%, 10%, 6%, and 2% [w/w]). The results indicated that an increase in the input voltage led to an increase in the rates of salt removal, electrical conductivity, and total soluble solids. The energy consumption increased whereas current efficiency and yield decreased significantly with an increase in input voltage and the salt removal level. Physicochemical proper- ties of the treated fish sauce, in terms of the total soluble solids, density, viscosity, ion concentrations (that is, Na + , K + ), total nitrogen, and color were significantly affected by the input voltage and the salt-removal level. Keywords: current efficiency, electrodialysis, energy consumption, ion concentration, low-sodium product, physicochemical properties, yield Introduction I t is currently well-known that people with a high intake of di- etary sodium have higher risk of suffering from high blood pres- sure and heart disease. A significant amount of salt may be taken into the human body through consumption of several cooking sauces. Among many types of cooking sauces, fish sauce is a popu- lar product, especially in East and Southeast Asia. This product has a unique and desirable flavor but contains high content of salt. This is because during a traditional production process of fish sauce, a large amount of salt needs to be added to preserve the product and obtain the desired flavor. Although many researchers have at- tempted to solve the previously mentioned problem by substitut- ing sodium with potassium in fish sauce (for example, Chayovan and others 1983), potassium-based fish sauce is still unsuitable for patients with kidney disease (National Kidney Foundation 2009). A technique that can be used for production of low-sodium fish sauce is thus required by the food industry. There are several possible processes that can be used to sepa- rate salt from any solution such as reverse osmosis, chromatogra- phy, nanofiltration, and ultrafiltration, but only a few methods can be applied on an industrial scale. Electrodialysis is one of the sep- aration techniques in which ion-exchange membranes and electric potential are utilized to separate ion species from an aqueous solu- tion (Choi and others 2002). Electrodialysis differs from other mem- brane techniques in that the separation principle is based on the electrical charge instead of the particle size (Baker 2004). Electrodialysis has been widely used for production of drinking water from sea and brackish water (Strathmann 1992; Ortiz and MS 20090295 Submitted 4/3/2009, Accepted 6/2/2009. Authors are with Dept. of Food Engineering, Faculty of Engineering, King Mongkut’s Univ. of Technology Thonburi, 126 Pracha u-tid Rd., Tungkru, Bangkok 10140, Thailand. Direct inquiries to author Devahastin (E-mail: sakamon.dev@kmutt.ac.th). others 2005). In addition, it can be used for water treatment and recovery of available substances from wastewater (Cros and others 2006). Electrodialysis is readily applicable in the food industry as it is easy to control, has high separation efficiency and can be used with feeds that have salt contents over a wide range (Strathmann 1992). In fact, there have already been considerable research ef- forts involving the use of electrodialysis in the food industry, for example, demineralization of raw cottage cheese whey (Johnson and others 1976), protein stability improvement of frozen skim milk and milk concentrate (Lonergan and others 1982), desalination of spent brine from pickled prune production process (Pan and oth- ers 1988), demineralization of whey protein concentrate (WPC) re- tentate and permeate (Perez and others 1993), desalination and acidification of seasoning solution from pickled ume (Japanese apricot) production process (Takatsuji and others 1999) and de- salination of salted duck egg white discarded as waste (Huang and others 1999). In addition, electrodialysis has been used to recover available substances (for example, nutrients, flavor, and aroma compounds) from many food by-products, such as desalination of silage juice to recover lactic acid and amino acid (Thang and others 2005) and desalination of seafood cooking juice to recover flavor and aroma compounds (Cros and others 2004, 2005; Atungulu and others 2007). One important precaution when applying electrodialysis to re- move salt from a food product, which is a different operation from desalination of sea or brackish water, is that the process can remove not only sodium chloride but also other important components in the product (Pan and others 1988). Therefore, a design of an elec- trodialysis system for a food product should involve a careful de- termination of a number of variables that may affect the operation and separation efficiency of the system. These variables include stack configuration, membrane properties, flow velocity, recovery rate and current density (Lee and others 2002). Moreover, feed properties such as pH, temperature, and concentration are factors C  2009 Institute of Food Technologists R  Vol. 74, Nr. 7, 2009—JOURNAL OF FOOD SCIENCE E363 doi: 10.1111/j.1750-3841.2009.01267.x Further reproduction without permission is prohibited