ABSTRACT
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Starch is produced by higher plants for energy storage and is the second largest biomass produced on earth, next to cellulose. Starch is also the major energy source in human and animal diets. Starch granules, consisting of highly branched amylopectin and primarily linear amylase (Chapter 1), are synthesized by apposition in amyloplasts of plants. Amylopectin and amylose molecules are organized in semicrystalline starch granules, and the outer chains of amylopectin molecules are arranged in double-helical crystalline structures.1 The native granular structure of starch, 2,3 with a specific density about 1.5 g/cm3,economizes the space for energy storage in seeds, grains, and tubers until it is ready to be utilized during germination. Transit starch in leaves, which is synthesized using sunlight and carbon dioxide during the daytime and hydrolyzed to glucose to be transported to storage organs at night, is in flat, small granule forms.4 The granular form of starch present in grains, tubers, and roots facilitates its isolation by gravity and by centrifugation during wet milling. The granular structure of starch also makes it possible to conduct chemical reactions followed by washing to produce chemically modified starches
that are used as commodity products for food and industrial applications.5 Major markets of starch applications are in corn syrups, high-fructose corn syrup, paper, textile, and food industries. In recent years, there is increasing demand in alcohol fuel produced from starch fermentation to partially replace gasoline and to increase the octane number of the fuel. Alcohol containing gasoline has been reported to reduce air pollution. Readers are encouraged to refer to other chapters for information on starch structures1,6 and properties.7
