Hydrolyzed Lactose Syrup from Concentrated Sweet Whey Permeates

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 .I0% lactic acid.The lactose hydrolysis rates were examined in 15% lactose whey permeates with yeast or fungal /3galactosidases at their optimum and low temperatures.Permeates containing 30, 22.5, 15, and 7.5% lactose were hydrolyzed with .22 to .66%yeast 18-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 101/ml to 1.8 x 103lmL However, during 1, 2, and 3 days of hydrolysis at 5°C, it increased from 4.0 x 101/ml to 4.1 x 10 I/ml, 4.8 x 101/ml, and 1.4x 102/ml, respectively.