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Stability of Concentrated, Decolorized, Deionized Hydrolyzed Whey Permeate¹

Department of Food Science, University of Wiscconsin-Madison, Madison 53706

ABSTRACT

Four separate lots of whey permeate from ultrafiltration of sweet cheese whey were deionized and decolorized to remove whey-like flavor and color, treated with ß-galactosidase to hydrolyze lactose, and concentrated. Variables introduced were levels of lactose hydrolysis and total solids; storage temperature; order of deionization, hydrolysis, and decolorization processes; and use of a 75°C posthydrolysis heat treatment. Each batch was evaluated for microbial stability, resistance to crystallization, and flavor after 3 mo storage at 37°C.

Concentration of permeate to less than 60% total solids resulted in microbial instability, and greater than 85% lactose hydrolysis resulted in galactose or lactose crystallization. Heating to 75°C and storing at elevated temperatures (up to 37°C) minimized crystallization. However, heating to 75°C accelerated browning. Flavor evaluation of browned samples suggested that caramelization rather than Maillard browning was the principal factor. Decolorizing with activated carbon after hydrolysis made no difference to the amount of sugar crystallization.

Lactose hydrolysis improved the stability of concentrated, decolorized, deionized hydrolyzed whey permeate. The syrup with longest storage stability was decolorized, 90% deionized, contained 85 to 90% hydrolyzed lactose, was concentrated to 65% total solids, heated to 75°C following concentration, and stored at 30°C.

¹ Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and by Wisconsin Dairies Cooperative, Baraboo, WI.