Study of solubility and mutarotation equilibrium of lactose in ethanol-water mixtures

Recovery of betaor alpha-lactose and its downstream processing require information about solubility data. Solubilities of lactose in various compositions of ethanol and water were measured gravimetrically. The solubility increased as the temperature increased but decreased with increasing ethanol percentage. The solubility was inversely fitted in a 4th polynomial model with increasing ethanol weight percentage. The simultaneous effects of temperature (T) and ethanol (E) on lactose solubility (Cs) could be expressed in a plane multiple regression of Cs = 11.85 - 0.29E + 0.25T, R2 = 0.80. The ratios of beta/alpha-lactose at equilibrium were measured with Gas Chromatography (GC) and polarimeter and they ranged from 0.08 to 1.37. In ethanol free solutions the ratio of beta/alpha- lactose increased with the rising temperature.