Acid-Catalyzed Hydrolysis of Lactose in Whey and Aqueous Solutions

Abstract

Lactose in fresh cottage cheese whey and aqueous solutions was successfully hydrolyzed in .5, 1, 2, and 3 Normal hydrochloric acid at 50, 60 and 70C. First-order rate constants and half-times were calculated from glucose released by hydrolysis. Rates in both whey and aqueous lactose solutions were comparable at 50 and 60C whereas at 70C whey lactose rates appeared consistently lower than aqueous lactose rates (by approximately 10 to 20%). This was attributed to loss of free glucose through the browning reaction. Undesirable side reactions were minimized by conducting the hydrolysis at temperatures well below 100C. The data demonstrate the feasibility of using mineral acid for whey lactose hydrolysis.Hydrolysis of lactose in whey (both acid and sweet) and aqueous solutions was unsuccessful at pH 4.7 and 90C being less than 1% after 96h of heat treatment. Hydrolysis was also insignificant in acid whey and aqueous lactose solutions containing 5 and 10% lactic acid after treatment for 150h at 60C.