Influence of lactic, citric and phosphoric acids on the properties of concentrated lactose solutions.

Physicochemical and thermal characteristics of concentrated lactose solutions containing 0.05, 1, or 4% (w/w) of three acids commonly used in the food industry, i.e., lactic, citric, and phosphoric acid, were studied. Properties of both lactose and water were affected by all acids studied. Thermographic analysis showed that interactions between water and acids hindered evaporation of water from most of lactose solutions. This effect was mostly related to the formation of a strong hydration layer around lactose molecules by hydrogen bonds. Acid-induced hydrolysis of lactose into glucose and galactose varied depending on the concentration, hydrolytic power of acids and molecular interactions in the system. The study concluded that the varying physical, chemical, structural and thermal characteristics of lactose as affected by the presence of different acids was mainly due to the manipulation of water-lactose interactions, whereas the hydrolysis of lactose by the acids plays a smaller role.