Lactose: Crystallization, hydrolysis and value-added derivatives

Lactose, the most abundant component of milk of most mammals, has been thoroughly studied for its physico-chemical properties, crystallization behavior and importance as a fermentation medium. Studies of various approaches to lactose modifications to increase its value as a food ingredient or nutraceutical component are more recent and presently predominate the research interest concerning lactose. This review, while summarizing briefly some physico-chemical properties and older studies concerning crystallization behavior (mutarotatory equilibrium, solubility, crystalline habit and form) focuses also on the modification alternatives to increase the utilization of lactose through value-added products. Various approaches to lactose hydrolysis leading to increased solubility, higher sweetness and expanded availability of milk and dairy products for lactose intolerant consumers are compared with an emphasis on crude enzyme extracts. Principles and processes for conversion of lactose to lactitol, lactobionic acid, lactulose, lactosucrose, and galacto-oligosaccharides are highlighted.