Whey electrodialysis

The fourth fully developed membrane process is electrodialysis, in which charged membranes are used to separate ions from aqueous solutions under the driving force of an electrical potential difference. The process utilizes an electrodialysis stack, built on the plate-and-frame principle, containing several hundred individual cells formed by a pair of anion- and cation-exchange membranes. The principal current appHcation of electrodialysis is the desalting of brackish groundwater. However, industrial use of the process in the food industry, for example to deionize cheese whey, is growing, as is its use in poUution-control appHcations. 

Leading Examples Electrodialysis has its greatest use in removing salts from brackish water, where feed salinity is around 0.05-0.5 percent. For producing high-purity water, ED can economically reduce solute levels to extremely low levels as a hybrid process in combination with an ion-exchange bed. ED is not economical for the produc tion of potable water from seawater. Paradoxically, it is also used for the concentration of seawater from 3.5 to 20 percent salt. The concentration of monovalent ions and selective removal of divalent ions from seawater uses special membranes. This process is unique to Japan, where by law it is used to produce essentially all of its domestic table salt. ED is very widely used for deashing whey, where the desalted product is a useful food additive, especially for baby food. 

Partly demineralized whey is produced by subjecting whey to electrodialysis or ion exchange processing treatments to prederen-tlally remove polyvalent ions, vacuum concentrated and spray dryed. 

Anon. 1968. Electrodialysis leads to whey profits. Food Eng. 40(1), 158. 

Proteins that remain in whey after removing casein from milk are recovered as whey protein concentrates by precipitation with added polyphosphate or other polyvalent anionic compounds, ultrafiltration, ion exchange adsorption, gel filtration, or a combined acid and heat precipitation process. Whey protein concentrates are also manufactured by a combined process involving electrodialysis, concentration, lactose crystallization, and drying (Richert 1975 Morr 1979 Marshall 1982 Anon. 1982 Muller 1982B). 

Batchelder, B.T. 1987. Electrodialysis applications in whey processing. Bull. Int. Dairy Fed. 212, 84—90. 

Greiter, M., Novalin, S., Wendland, M., Kulbe, K.-D., and Fischer, J. 2002. Desalination of whey by electrodialysis and ion exchange resins Analysis of both processes with regard to sustainability by calculating their cumulative energy demand. J. Memb. Sci. 210, 91-102. 

Mucchetti, G. and Taglietti, P. 1993. Demineralization of whey and ultrafiltration permeate by electrodialysis. Scienza e Tecnica Lattiero-Casearia 44, 51-62. 

Perez, A., Andres, L.J., Alvarez, R., Coca, J., and Hill, C.G. 1994. Electrodialysis of whey permeates and retentates obtained by ultrafiltration. J. Food Process Eng. 17, 177-190. 

The two water desalination applications described above represent the majority of the market for electrodialysis separation systems. A small application exists in softening water, and recently a market has grown in the food industry to desalt whey and to remove tannic acid from wine and citric acid from fruit juice. A number of other applications exist in wastewater treatment, particularly regeneration of waste acids used in metal pickling operations and removal of heavy metals from electroplating rinse waters [11]. These applications rely on the ability of electrodialysis membranes to separate electrolytes from nonelectrolytes and to separate multivalent from univalent ions. 

Electrodialysis is a well-proven technology with a multitude of systems operating worldwide. In Europe and Japan, electrodialysis dominates as a desalting process with total plant capacity exceeding that of reverse osmosis and distillation [3]. Electrodialysis with monopolar membranes is applied to different food systems, to demineralization of whey [5-8], organic acids [9], and sugar [10,11], separation of amino acids [12] and blood treatments [13], wine stabilization [14—16], fruit juice deacidification [17-19], and separation of proteins [20-22]. These applications use the sole property of dilution-concentration of monopolar lEMs in a stack of as many as 300 in an electrodialysis cell. 

During electrodialysis treatment, total Mg " " concentration in the STW diminished from 980 to 800 ppm in 30 min a 18.4% decrease from the initial concentration. This decrease in Mg concentration is due to Mg migration, from the STW solution to the concentrate compartment where its concentration increases proportionally. Eor cheese whey and skimmed milk, Hiraoka et al. [165] showed that at the early period of demineralization and CP are initially removed followed by calcium, magnesium, and phosphoms. However, deashing rate of about 60% and 30% for cheese whey and skimmed milk, respectively, had to be reached before Mg started to migrate. In our case, about 22% of demineralization was reached at the end of the ED configuration. 

Recently, Lin et al. [184] used EDBM technology for acidification and decreasing the ionic strength of a fresh cheddar cheese whey. In this study, EDBM process was carried out with or without preliminary decrease of whey mineral salts content by conventional electrodialysis to obtain precipitates with high level of lipids (Figure 21.36). After centrifugation of the treated whey, composition of floes and precipitation yields was determined. 

Whey centrifugation at 1000 g during 5 min (process 1) allowed a 20.8% recovery of cheddar cheese whey initial lipids (Table 21.10). The other components, proteins and lactose were precipitated at a lower rate (1.1% and 0.6%, respectively). A 32.1 % whey lipid precipitation was obtained in process 2 consisting of an electroacidification to reach a pH value of 3.7 before the centrifugation step. This represents a 54% increase of precipitation rate in comparison with process 1, with proteins and lactose precipitation levels quite similar (1.9% and 0.9%, respectively). Demineralization step before electroacidification had only small effect on the precipitation level Similar precipitation levels for lipids and lactose were obtained in comparison with process 2 values except for proteins. Conventional electrodialysis allowed an increase of protein precipitation from 1.9% to 3.3% (Table 21.11). 

FIGURE 21.36 Cheddar cheese whey treatment hy conventional electrodialysis and EDBM before final centrifugation. 

Batchelder BT. Electrodialysis applications in whey processing. International Whey Conference, Chicago, IE, October 28, 1986. Paper no TP 343 ST. 

Perez A, Andres LJ, Alvarez R, Coca J, and Hill CG. Electrodialysis of whey permeates and retentates obtained by ultrahltration. J. Food Proc. Eng. 1994 17 177-190. 

Hiraoka Y, Itoh K, and Taneya S. Demineralization of cheese whey and skimmed milk by electrodialysis with ion exchange membranes. Milchwiss 1979 34 397-400. 

Food industry and medical supplies Edible salt production from seawater,23 demineralization of whey,24 recovery of amino acids from fermentation liquor,25 separation of amino acids,26 preparation of lactic acid27, gluconic acid28 amino acids,29 etc. from their salts, stabilization of grape juice30 and pre-treatment of wine,31 deacidification of sour orange juice,32 desalination of soups, desalination of soybean sauce,33 continuous fermentation in the presence of electrodialysis,34 de-ionization of sugar solution.35... 

Figure 6.18 Complete and effective demineralization of whey by electrodialysis in combination with ion exchange resins (after softening the whey with a cation exchange resin column, electrodialysis is performed to complete removal of the minerals economically).

S. Okonogi, Progress in practice of membrane separation techniques in dairy industry, Nihon Shokuhin Kougyou Gakkaishi (J. Food Ind. Jpn.), 1985, 32, 144—155 Y. Kobuchi and H. Motomura, Demineralization of whey by multistage continuous electrodialysis, International Membrane Technology Conference, Nov. 8-10 (1983), Sydney. 

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