淀粉及变性淀粉外文资料.ppt

Chapter 4 The Carbohydrates: Sugars, Starches, and Fibers The Chemist’s View of Carbohydrates Carbohydrates are made of carbon, hydrogen and oxygen atoms. These atoms form chemical bonds that follow the laws of nature. The Simple Carbohydrates Monosaccharrides are single sugars (most are hexoses). Glucose serves as the essential energy source, and is commonly known as blood sugar or dextrose. Fructose is the sweetest, occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup. Galactose rarely occurs naturally as a single sugar. The Simple Carbohydrates Disaccharides are pairs of monosaccharides, one of which is always glucose Condensation reactions link monosaccharides together. Hydrolysis reactions split molecules and commonly occur during digestion. Maltose consists of two glucose units. It is produced during the germination of seeds and fermentation. Sucrose is fructose and glucose combined. It is refined from sugarcane and sugar beets, tastes sweet, and is readily available. Lactose is galactose and glucose combined. It is found in milk and milk products. The Complex Carbohydrates Few (oligosaccharides) or many (polysaccharides) glucose units bound/linked together in straight or branched chains. The Complex Carbohydrates Glycogen Storage form of glucose in the body Provides a rapid release of energy when needed Starches Storage form of glucose in plants Found in grains, tubers, and legumes The Complex Carbohydrates Dietary fibers provide structure in plants, are very diverse, and cannot be broken down by human enzymes. Soluble fibers are viscous and can be digested by intestinal bacteria (this property is also known as fermentability). These fibers are found in fruits and vegetables. Insoluble fibers are nonviscous and are not digested by intestinal bacteria. These fibers are found in grains and vegetables. The Complex Carbohydrates Fiber Sources Dietary fibers are found in plant foods. Functional fibers are