Polysaccharides.ppt
- 1. Polysaccharides Mrs. R.Subha, M.Sc., M.Phil., D.C.T., Assistant Professor of Home Science
- 2. Introduction • Polysaccharides also play important roles in our lives. • Starch is the most common type of complex carbohydrate which is present in the food we consume. • They are complex carbohydrates formed with a chain of monosaccharides. • The bonds that keep the chain together are glycosidic. • Some common Polysaccharides examples are starch, glycogen, and cellulose.
- 3. • Polysaccharides can also be defined as the long polymers of carbohydrates that are made up of repeating mono- or di-saccharide units joined by glycosidic connections (e.g., glucose, fructose, galactose). • They might be linear or very branching in structure. • Storage Polysaccharides like starch and glycogen, as well as structural Polysaccharides like cellulose and chitin, are just a few examples. • More than 10 monosaccharide units make up a Polysaccharide.
- 4. Characteristics of Polysaccharides • They are not sweet in taste. • Many are insoluble in water. • They are hydrophobic in nature. • They do not form crystals on desiccation. • Can be extracted to form a white powder. • They are high molecular weight carbohydrates. • Inside the cells, they are compact and osmotically inactive. • They consist of hydrogen, carbon, and oxygen. • The hydrogen to oxygen ratio being 2:1.
- 6. 1.Starch • It occurs in cereal grains, pulses, tubers, fruits etc. • It is the major source of energy in diet of man. • Starch is a polymer of glucose. • Starch is a mixture of two substances, about 25% amylose (straight-chain polymer) and 75% amylopectin (branched chain polymer). Because of the structural differences between amylose and amylopectin, they exhibit different properties. • Amylose contributes to gel-formation while Amylopectin is responsible for thickness properties of foods containing starch. • Amylose & Amylopectin chains in granules – semi- crystalline structure – retards their digestion by pancreatic amylase
- 7. Starch classification • Starch has been classified as • rapidly digestible starch • slowly digestible starch • resistant starch ( depending upon its digestion profile)
- 10. Resistant starch • Starch and Starch degradation products escapes digestion in small intestine & available for fermentation by microflora in large intestine. • The body cannot easily digest this form of starch, and it can pass through the digestive system untouched, similar to dietary fiber. • It may support healthy intestinal microflora. RS1 - physically inaccessible starch exists in grains, seeds, and beans & in processed starchy foods ex. Pasta. RS2 - Starch that escapes digestion in Small Intestine because of ungelatinised granules in raw potatoes and unripe bananas highly resistant to hydrolysis by pancreatic amylase. RS3 - retrograded amylose formed during cooling of gelatinized starch (foods that undergo cooking then cooling)such as rice and cornflakes. RS4 – produced by modifying the starch to introduce chemical bonds that leave starch not readily digested - chemically modified starches is bread.
- 11. 2. Dextrins • Degradation products of starch in which polymers broken down to smaller units by partial hydrolysis • Main source of CHO in proprietary preparation – used as oral supplements for tube feeding. • Liquid glucose – mixture of dextrins, maltose, glucose and water – used in products easily assimilated form to patients who are seriously ill. • They are larger molecules than sucrose/glucose & have less osmotic effect.
- 12. Nonstarch polysaccharides (NSPs) • occur naturally in many foods. • The physiochemical and biological properties of these compounds correspond to dietary fiber. • Ex. Arabinose, Xylose, Mannose, Galactose, Glucose and Uronic acids
- 13. Reference • Srilakshmi B.(2022). Nutrition Science. 7th Edition. New Age International (P) Ltd., • http://ecoursesonline.iasri.res.in/mod/page/vi ew.php?id=90238 • https://byjus.com/biology/polysaccharides/ • https://www.vedantu.com/chemistry/polysac charides