Lecture+08

Gelatinizationandretrogradationmcgeep458seefigures

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Unformatted text preview: ysaccharides (McGee p.804‐5) Starch is deposited in plants as granules. It is a storage carbohydrate of plants, such as cereal grains (wheat, rice, corn); root vegetables (potatoes); legume seeds (beans, lentils). Starch polymers are composed of glucose units, forming two types of chain: a linear chain called amylose and a branched chain called amylopectin. Gelatinization and Retrogradation (McGee p.458, see figures). Bread staling and starch retrogradation (McGee p.541‐2 “The Staling Process..”). Reheating may reverse bread staling. Retrogradation proceeds more quickly in the fridge. Sweeteners from corn: corn syrup and high‐fructose corn syrup (HFCS); see McGee p.677. Corn contains ~70% starch, which can be hydrolyzed by enzymes and acids. Enzymatic hydrolysis of starch can be carried out by amylases. There are different types of amylases; which split starch differently, some in a random attack, others split from the end of the chain. A complete hydrolysis of starch produces only glucose. Frequently, starch hydrolysis is not complete, as in the production of the most common grade of corn syrup, which contains glucose, maltose and dextrins . These syrups are viscous, l...
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