HPLC and NMR Study of the Reduction of Sweet Whey Permeate

Sweet whey permeate was hydrogenated under high pressure and temperature with Raney Ni as a catalyst. Different reaction conditions, such as reaction time, amount of catalyst, and initial hydrogen pressure and temperature, were studied. The reaction mixtures were analyzed by HPLC and NMR. The major whey component, lactose (4- O -β- d -galactopyranosyl- d -glucose), was converted under these conditions to lactitol (4- O -β- d -galactopyranosyl- d -glucitol) to different degrees. Hydrolysis of lactose to galactose and glucose and further reduction was also observed over a wide temperature range, whereas isomerization of lactose to lactulose (4- O -β- d -galactopyranosyl- d -fructose) and subsequent reduction only occurred above 110 °C. With reaction time of 4 h, an initial hydrogen pressure of 1500 psi, 40.5 g of Raney Ni, and a temperature = 120 °C, sweet whey permeate (42%, 340 g) gives lactitol (85.2 %), lactulitol (1.7%), and sorbitol and dulcitol (0.8%) together with unreacted fat, protein, and salts (12.3%).