ABSTRACT
Fresh milk is an example of a naturally occurring emulsion that can be consumed directly by human beings (Swaisgood, 1996). In practice, however, most milk is subjected to a number of processing operations prior to consumption in order to ensure its safety, to extend its shelf life, and to create new products (Robinson, 1993, 1994; Walstra, 1999). Processing operations, such as homogenization, pasteurization, whipping, chilling, freezing, churning, enzyme treatment, and aging are responsible for the wide range of properties exhibited by dairy products, for example, homogenized milk, cream, ice cream, butter, and cheese (Section 12.2). Unlike dairy products, most other food emulsions are manufactured by combining raw materials that are not normally found together in nature (Dickinson and Stainsby, 1982; Dickinson, 1991; Stauffer, 1999; Friberg et al., 2004). For example, a salad dressing may be prepared using water, proteins from milk, oil from soybeans, vinegar from apples, and polysaccharides from seaweed. The physicochemical and sensory properties of a particular food emulsion depend on the type and concentration of ingredients that it contains, as well as the method used to create it. To improve the quality of existing products, develop new products, and reduce production costs it is important for food manufacturers to have a thorough understanding of the physical processes that take place during emulsion formation. This chapter discusses the physical principles of emulsion formation, the various techniques available for creating emulsions, and the factors that affect the efficiency of emulsion formation. It should be mentioned that this chapter focuses on mechanical methods of producing emulsions, rather than on chemical or spontaneous emulsification methods (Vincent et al., 1998), since these latter methods are rarely used in the food industry.
