Concentration of whey

Membrane Sep r tion. The separation of components ofhquid milk products can be accompHshed with semipermeable membranes by either ultrafiltration (qv) or hyperfiltration, also called reverse osmosis (qv) (30). With ultrafiltration (UF) the membrane selectively prevents the passage of large molecules such as protein. In reverse osmosis (RO) different small, low molecular weight molecules are separated. Both procedures require that pressure be maintained and that the energy needed is a cost item. The materials from which the membranes are made are similar for both processes and include cellulose acetate, poly(vinyl chloride), poly(vinyHdene diduoride), nylon, and polyamide (see AFembrane technology). Membranes are commonly used for the concentration of whey and milk for cheesemaking (31). For example, membranes with 100 and 200 p.m are used to obtain a 4 1 reduction of skimmed milk. 

Whey concentration, both of whole whey and ultrafiltration permeate, is practiced successfully, but the solubility of lactose hmits the practical concentration of whey to about 20 percent total sohds, about a 4x concentration fac tor. (Membranes do not tolerate sohds forming on their surface.) Nanofiltration is used to soften water and clean up streams where complete removal of monovalent ions is either unnecessary or undesirable. Because of the ionic character of most NF membranes, they reject polyvalent ions much more readily than monovalent ions. NF is used to treat salt whey, the whey expressed after NaCl is added to curd. Nanofiltration permits the NaCl to permeate while retaining the other whey components, which may then be blended with ordinaiy whey. NF is also used to deacidify whey produced by the addition of HCl to milk in the production of casein. 

Reverse osmosis (RO) pressure difference desalination of sea/brackish water concentration of whey and fruit juice waste water treatment... 

Electrophoresis on cellulose acetate strips has also been used for the rapid resolution of whey proteins (Bell and Stone 1979). Samples of a 10 1 concentrate of whey are applied to cellulose acetate strips which have been saturated with Tris-barbiturate buffer, pH 8.6, ionic strength 0.097, and the electrophoresis is performed at 225 V for 1 hr. This procedure separates not only the major whey proteins but also their genetic variants. 

The principal current applications of UF are the separation of oil from emulsified ofl wastes recovery of paint from electro-coat paint rinse tanks and the concentration of whey, a by-product in cheese making In all of these applications, the proces is governed by cake formation. Under these circumstances, the only requirements of the UF membrane are ... 

Application of RO in the partial demineralization or pre-concentration of whey, and the treatment of dairy effluents. 

Application of NF in the simultaneous demineralization and concentration of whey, concentration of lactose from the permeate of the UF whey, and the purification of membrane cleaning solutions. 

To date, the fractionation and concentration of whey proteins from cheese whey remain to be one of the more successful industrial applications of UF [22-24]. Due to flux decline during operation, however, Mulvihill and Ennis [38] reported that the practical limit for whey concentration by UF in modem plants is around 24% total solids, with a protein total solids ratio limit of -0.72 1. DF is used to achieve a higher ratio of protein to total solids, -0.80 1, and a total solids content of about 28% [38]. 

Today direct concentration of whey is known and accepted as an exceedingly attractive supplement or alternative to evaporation. 

Set up 12 test tubes (10 X 100 mm, colorimetric tubes) and add water and proteins according to the top three rows of Table E4.2 Tube 1 is used as a blank and tubes 2 through 6 are for construction of a standard calibration curve. Tubes 7 to 10 are duplicates of two different concentrations of the isolated a-lactalbumin solution, and tubes 11 and 12 are two concentrations of whey. Water is added to give a final volume of 1 0 mL m each tube Add 5,0 mL of dilute Bradford dye reagent to each tube and mix well by gentle inversion After a period of at least 5 minutes, read for each tube, using tube 1 as a blank The tubes should be read within an hour after adding the... 

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