Fats: Physical properties

Abstract

The physical properties of fats and oils are of great practical importance so it is necessary to understand the makeup of these materials and how they should be used (1-9). Thus, many technical applications of fatty materials, including their uses in edible products, depend on the oiliness, surface activity, solubility, melting behavior, or other physical properties peculiar to long-chain compounds (10). Because fats and oils are mainly composed of mixtures of triacylglycerols, the physical properties of these molecules are going to determine the physical characteristics of the oil or fat. Thus, these characteristics are dependent on such factors as seed or plant source, degree of unsaturation, length of carbon chains, isomeric forms of the constituent fatty acids, molecular structure of the triacylglycerols, and processing. This chapter will review the most important physical properties of triacylglycerol molecules as well as of the most common edible fats and oils. Crystallization from solution is usually a slow process that first requires supercooling and then leads to nucleation and crystal growth. A high degree of supercooling will be conductive to nucleation, and very small crystals will be formed. At temperatures closer to the crystallization point, crystal growth will be favored and large crystals will be formed (2). Once formed, crystals, which may be stable or metastable, are able either to modify their habit or undergo phase transitions, respectively. Both processes result in polymorphic behavior, a behavior common to fats and other lipids (11-22).