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Hydrolyzed Lactose Syrup from Concentrated Sweet Whey Permeates

Department of Food Science, Cornell University, Ithaca, NY 14853

ABSTRACT

Ultrafiltration of reconstituted demineralized sweet whey at 52°C resulted in a clear permeate containing 30.0% lactose, 1.06% total protein, .02% fat, .30% ash, and .10% lactic acid. The lactose hydrolysis rates were examined in 15% lactose whey permeates with yeast or fungal ß galactosidases at their optimum and low temperatures. Permeates containing 30, 22.5, 15, and 7.5% lactose were hydrolyzed with .22 to .66% yeast ß-galactosidase, based on lactose content, at 40°C and pH 6.5 for 5 h. Maximum hydrolysis, about 87 to 100%, occurred in the substrate containing 15% lactose.

An almost colorless, highly sweet syrup was produced by the hydrolyzed permeate containing 15% monosugars subjected to .2% activated carbon and subsequent concentration at 40 to 45°C under vacuum.

During 5-h hydrolysis at 40°C, the standard plate count increased from 5.0 x 1O¹/ml to 1.8 x 1O³/ml. However, during 1, 2, and 3 days of hydrolysis at 5°C, it increased from 4.0 x 10³/ml to 4.1 x 1O¹/ml, 4.8 x 1O¹/ml, and 1.4 x 1O²/ml, respectively.