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ABSTRACT
The physical characteristics of milk powders used in chocolate can have significant impact on the processing conditions needed to make that chocolate and the physical and organoleptic properties of the finished product. Four milk powders with different particle characteristics (size, shape, density) and "free" milk fat levels (easily extracted with organic solvent) were evaluated for their effect on the processing conditions and characteristics of chocolates in which they were used. Many aspects of chocolate manufacture and storage (tempering conditions, melt rheology, hardness, bloom stability) were dependent on the level of free milk fat in the milk powder. However, particle characteristics of the milk powder also influenced the physical and sensory properties of the final products.
(Key words: milk powder, chocolate, milk fat, rheological property)
Abbreviation key: AMF = anhydrous milk fat, HFW = powder made by drying cream and skim milk powder together, LSN = low-heat, spray-dried skim (nonfat) milk powder, LSW = low-heat, spray-dried whole milk powder, RDW = roller-dried whole milk powder, SMP = skim milk powder, WMP = whole milk powder.
INTRODUCTION
Over the years, a number of different types of milk powders have been explored for use in chocolates (Haylock, 1995). These include roller-dried and spray-dried whole milk powders (WMP), high-fat powders, buttermilk powders, whey powders, and skim milk powder sprayed with anhydrous milk fat (AMF) or cream. The characteristics of these powders are quite different, although they may have similar composition. Characteristics of milk powders of specific importance to milk chocolate manufacture include degree of free fat, particle size and structure, and air inclusion (Twomey and Keogh, 1998). Powders that contain high free fat, or fat that is easily extractable and can interact directly with the cocoa butter in chocolate, typically have been desired by milk chocolate manufacturers (Hansen and Hansen, 1990). The high free fat level results in reduced chocolate viscosity, making it easier to process the chocolate and providing an economy in cocoa butter savings (cocoa butter is usually added to control viscosity).
Numerous factors, not just free fat level, affect the properties of chocolates made with milk powder addition. Table 1 summarizes the properties of milk powders that can potentially influence chocolate characteristics. Characteristics such as particle size and density, internal structure, color, and...