Structural Transitions and Related Physical Properties of Starch

Publisher Summary The functional properties of starch depend on a number of integrated factors, which include polymer composition, molecular structure, interchain organization, and minor constituents such as lipids, phosphate ester groups, and proteins. Chemical, enzymic, and physical modification of starch, with either preservation or destruction of the native granule, broaden the functionality-imparting properties of different starches. The greatest challenge is to relate physicochemical properties and functions of starch with information on various levels of structure. There is a diversity of structures depending on starch source, amylose–amylopectin ratios, lipid, moisture and plasticizer contents, and thermo-mechanical histories. In addition to difficulties in describing and quantifying the structural morphology of starch materials, the ultra structural level of starch also presents a great challenge. This chapter discusses some aspects of phase transition behavior and other material properties of starch, particularly as they pertain to the structural order and interactions of the starch polysaccharides with water, lipids, and other solutes. Understanding the thermally induced structural transitions of starch is helpful in controlling its physical properties and processing behaviors (e.g. plasticization, viscosity), as well as in designing products with improved properties (e.g. texture, stability). The description of the state and phase transition behavior of starch systems is focused on with an emphasis on their molecular organization and their response to various environments (temperature, solvent, other cosolutes). Selected material properties are also discussed in an effort to demonstrate structure–function relationships of this biopolymer mixture in pure systems and in real food products.