ABSTRACT
Fresh milk is an example of a naturally occurring emulsion that can be consumed directly by human beings. In practice, however, most milk is subjected to a number of processing operations prior to consumption to ensure its safety, to extend its shelf-life, and to create new products. Processing operations, such as homogenization, pasteurization, whipping, 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 (Chapter 12). Unlike dairy products, most other food emulsions are manufactured by combining raw materials that are not normally found together in nature. 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 it contains, as well as the production method used to fabricate 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 efciency of emulsion formation. In general, the homogenization methods used to form emulsions can be divided into two categories: high-energy and low-energy methods. High-energy methods typically use specialized equipment (homogenizers) capable of generating intense disruptive forces to intermingle and disrupt oil and water phases. On the other hand, low-energy methods rely on the spontaneous formation of small droplets (usually in surfactant, oil, and water systems) when conditions such as temperature or composition are changed in a specic manner. Most food emulsions are currently produced by highenergy methods, and so they will be the main focus of this chapter. However, low-energy methods are utilized for certain specialist applications within the food industry (e.g., production of some beverage emulsions), and so they will also be considered.
