Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Lactose is used in many food/pharmaceutical products, despite powders containing amorphous lactose being difficult to handle because they tend to be sticky and are prone to crystallization and powder caking. There is therefore a market for lactose powder with improved functionality to facilitate powder handling. The aim of the proposed project was to produce a value-added, free-flowing and non-caking lactose powder that can be easily blended into other dairy products, such as dry-powder soups or drinks, and non-dairy products such as chocolate bars. The principle of particle coating during spray drying (in-situ coating), which exploits the phenomenon of solute segregation of different components within the drying droplet, was used for the purpose of producing such powders. In this work, spray-dried lactose powders containing low concentrations of edible additives, such as proteins, polymers or fat, were produced in order to investigate the ability of these additives to accumulate at the droplet surface during drying to form a coating that improves powder functional properties and limits powder caking. This thesis presents the results of the trials necessary to develop these coated powder by the use of an

Doctor of Philosophy / Food Science Institute / Jayendra K. Amamcharla / Lactose is commercially produced from whey, whey permeate, or milk permeate as α-lactose monohydrate in crystalline form. Focused Beam Reflectance Measurement (FBRM) as a potential tool for in situ monitoring of lactose crystallization at concentrations relevant to the dairy industry was evaluated. Applicability of FBRM at supersaturated lactose concentrations 50%, 55%, and 60% (w/w) was reported in comparison with Brix values obtained from a Refractometer during isothermal crystallization at temperatures 20ºC and 30ºC. FBRM technique was shown to be a valuable tool for monitoring chord length distributions during lactose crystallization. In a different study, the influence of cooling rate during crystallization of lactose in concentrated permeates was studied. Three cooling rates accounting for approximately 17, 11, and 9 h were applied during lactose crystallization to evaluate the lactose crystal yield and quality of lactose crystals. There was no significant difference (P>0.05) found in lactose crystal yield, mean particle size obtained at the end of crystallization. This study suggested that increasing the cooling rate during lactose crystallization within the range explained in this study can save approximately 8 h of crystallization time. These studies evaluated FBRM as a potential tool to monitor lactose crystal chord lengths and counts. Also, process improvements were suggested to increase the productivity of lactose crystallization process by reducing the crystallization time. In chapters 5 and 6, calcium-reduced milk protein concentrates (MPCs) were used as an ingredient to improve the stability of high-protein dairy beverages. Heat stability increased significantly (P>0.05) in 8% protein solutions made from 20% calcium-reduced MPC. A significant increase in heat stability was observed in beverages formulated with 20% calcium-reduced MPC in the absence of chelating agent. In another study, it was evident that the dairy beverage formulation with 20% calcium-reduced MPC showed no sedimentation and age gelation indicating an improved storage stability. These studies confirmed that 20% calcium reduced MPC contributed towards improved heat stability and storage stability of the high-protein beverages.