Starches
Pages 25-30
DOI: https://doi.org/10.1094/1891127012.003
ISBN: 1-891127-01-2
Abstract
Topics Covered
- Gelatinization
- Pasting
- Retrogradation
- Effects of pH, Shear, and other Ingredients
Introduction to Chapter
Native starch granules are essentially insoluble in cold water. Thus, the unique characteristics of many of our foods, from the mouth-feel of gravies to the texture of gum drops and pie fillings, are the results not of inherent properties or behaviors of native granules, but of the changes they undergo when they are heated with water.
The first of these changes are gelatinization and pasting. They are irreversible and dependent in complex ways on the amount of heat and water available to the system. These changes render all or part of the material in granules soluble and consequently able to contribute to food properties such as texture, viscosity, and moisture retention. The third change, retrogradation, involves reassociation of the molecules and occurs after heating. The rate and extent of retrogradation are also dependent on temperature but in a manner different from that of gelatinization and pasting.
This discussion of gelatinization, pasting, and retrogradation focuses solely on granular native starch. It is extremely important to keep in mind that the modification of native starches, via chemical, physical, and/or enzymatic treatment, can dramatically alter their properties—usually making them better suited for food applications. In fact, because of the limitations inherent in native starches, most food products are formulated with their modified counterparts. The modification of starch is discussed in Chapter 4.
Depending upon the botanical source, native starches exhibit different behavior during pasting; i.e., no two types of starches are alike. Because so-called cook-up starch is typically used in food systems at about 2–6% by weight of the final product, the following discussion is based on characteristics at or near this concentration range.
