General Reaction Characteristics of Dextrinization

Much work has been performed on the pyrolysis of starch at temperatures near 200°, for it is under these conditions that many commercial dextrins are prepared. 

It should be noted that there are three important classes of industrial pyrodextrin, and each of these has its own characteristic color, viscosity, and solubility in cold water. The types of dextrin are  

White dextrins, formed when starch is heated at low temperatures (79-120°) in the presence of acid catalysts, usually hydrochloric acid, for short times (3-8 hr.). Under these conditions, no color develops in the product. 

Yellow, or canary, dextrins, formed when starch is heated at higher temperatures (150-220°) in the presence of acidic catalysts for longer times (6-18 hr.). The product then has a yellow to brownish color. 

British Gums, formed when starch is heated at temperatures of 130-220° for periods of 10-20 hr. Considerable color develops before solubility in water is achieved. 

---