chapter  3
32 Pages

Lipid Phase Behavior

WithK. L. Humphrey, Suresh S. Narine

A phase is a domain, homogenous with respect to chemical composition and physical state [1,2]. Some natural fats are examples of systems of coexisting homogeneous domains that are not necessarily in equilibrium. The phases within a fat system may be categorized in terms of liquid/solid, polymorphic forms, and volume expansion upon crystallization of the fat. Because many physical definitions of a phase exist, it is important to define very carefully what is used as a phase in any particular study of lipids. For example, within the solid phase of a fat there can exist many different polymorphs, and

within each polymorphic type there can exist many different microstructures. Therefore, clear definitions of what constitutes a phase are important in any particular study. The relationship and occurrence of phase change in a fat system is referred to as the phase behavior of the lipid. Phase behavior, such as that obtained through the study of the solid fat content (SFC), dilatometry, melting behavior, and/or polymorphism of a lipid sample, is important in optimizing production processes and maintaining production quality, and has been used in the past to predict important attributes such as mouth-feel and hardness in fat-containing food products. Studies of phase behavior also help to provide a better understanding of the ways in which fat blends interact; an important aspect since the large-scale industrial production of shortenings and other fatcontaining products often require blending of lipids from many different sources.