© TANUVAS, NATURALLY OCCURRING CARBOHYDRATES IN FOOD

© TANUVAS, 2011 Learning objectives After completing this chapter learner should be able to: 1.understand the structures and purposes of basic components of eukaryotic cell, especially macromolecules, membranes, and organelles 2.understand the terms used to describe chromosome morphology 3.become familiar with diploid chromosome number in livestock and poultry

© TANUVAS, 2011 Introduction Nature commonly utilizes carbohydrates as source of energy, structure- forming material, water-maintaining hydrocolloids and even sex attractants. Amino acids synthesize in the concentrated space and polymerize into proteins on already-available polysaccharide matrices. Carbohydrates are organic compounds containing carbon, hydrogen and oxygen with the general formula C n (H 2 O) n. They may be simple or complex molecules. Important food carbohydrates include simple sugars, dextrins, starches, celluloses, hemicelluloses, pectin, and gums.

© TANUVAS, 2011 They are an important source of energy or fiber in the diet and they are important constituents of food because of their functional properties. They are used as sweeteners, thickeners, stabilizers, gelling agents, and fat replacers. The simplest carbohydrates are called monosaccharides or sugars and they have the general formulae C n H 2n O n. The most common ones contain six carbon atoms. Disaccharide contains two sugar units, trisaccharides contain three, oligosaccharides contain several units, and polysaccharides are complex polymers containing as many as several thousand units of monosaccharides linked by means of glycosidic bonds.

© TANUVAS, 2011 Monosaccharides Monosaccharides are simple carbohydrates containing between three and eight carbon atoms, but only those with five and six carbon atoms are common. Most important ones are glucose and fructose with general formula C 6 H 12 O 6. Glucose is an aldose as it contains an aldehyde group. Fructose is a ketose as it contains a keto group.

© TANUVAS, 2011 Monosaccharide and their natural derivatives Pentoses L-Arabinose D-xylose Plant gums, hemicellulose, saponins, protopectin Accompanies L- arabinose Alcoholic fermentation, furan-2, aldehyde production Reduction to xylitol sucrose substitute; alcoholic fermentation; production of furan-2 aldehyde

© TANUVAS, 2011 Hexoses D-Glucose D-Fructose D-Galactose L-Fucose D-Mannose L-Rhamnose Plants and animals, honey, inverted sugar, saponins Fruit, traces in plant honey, Constituent of milk, dairy products (Milk sugar) algae, plant mucus and gums Oligo-and polysaccharides, plant mucus and gums, saponins, glycosides Algae, plant mucus. Plant mucus and gums, pectins saponins, glycosides Alcoholic fermentation; sweetener ; energy pharmacopeial material; nutrient; food preservative Preparation of dairy products Preparation of mannitol, which is used as an alternative sweetener in food products

© TANUVAS, 2011 Hexuloses D-Fructose D-Glucosylamine L-Sorbose Fruits, honey, inverted sugar maple syrup Chitin, Chitosan Rowan berries Noncavity-causing sweetener; sweetener for diabetics; food humidifier and preservative Pharmaceutical aid; antiarthritic drugs; ion exchanger Synthesis of ascorbic acid

© TANUVAS, 2011 Disaccharides Disaccharide contains two monosaccharides linked together by glycosidic bond. Sucrose or the table sugar is the most common disaccharide. It contains glucose and fructose linked by α -1, 2-glycosidic bond. Maltose contains two glucose units linked by α 1-4 glycosidic bond. Lactose known as milk sugar contains one glucose and one galactose molecules. Maltose is the building block of starch, which contains

© TANUVAS, 2011 Disaccharides Lactose Maltose Sucrose Mammalian 'milk Starch, sugar beet, honey Sprouted grain, hydrolysis of starch Sugar beet, sugar cane, maple syrup Dairy product taste improver; fermenting component of milk Food fermentation; Common sweetener; caramel production; food preservation

© TANUVAS, 2011 Oligosaccharides Oligosaccharides contain 3-10 monosaccharide units linked together by glycosidic bonds. Common ones include raffinose and stachyose. Raffinose is a trisaccharide with galactose, glucose and fructose. Stachyose contains glucose, fructose and two galactose units. Both occur in legumes and dry beans and peas. They are not hydrolyzed or digested by human digestive system and become food for bacteria in the large intestine.

© TANUVAS, 2011 Polysaccharides Polysaccharides contain more than 10 monosaccharide units linked together by glycosidic bond. The most important polysaccharides are starches, pectins and gums. All are complex polymers with different properties, which depend on the mono saccharides that make up the structure the linkage by which they are linked and the degree of branching of the molecules.

© TANUVAS, 2011 Occurrence All organism cells, including those of animals, contain components of carbohydrates in their membranes. Frequently, carbohydrates exist in naturally derivatives forms, including aminated forms, as in chitin and chitosan; esterified; alkylated as in glycosides; oxidized; reduces; or linked to proteins, lipids, and other structures such as glycoproteins. Lower monosaccharides, such as aldotrioses and aldo-and ketotetroses, do not exist naturally in a free state. Glyceraldehyde in phosphorylated form is the product of alcoholic fermentation and glycolic sequence. Erythrose, an aldotetrose, and erythrulose, a ketotetrose, also appear in phosphorylated from in the pentose cycle of glucose, while ketopentose-ribulose can be found as its phosphate ester.

© TANUVAS, 2011 Several common and uncommon carbohydrates (erlose, turanose, trehalose, isomaltose, melecitose) have been found in honey. In nature, various carbohydrates derivatives are also found. Among them are so-called sugar alcohols (auditors). They are the natural products of the reduction of monosaccharide. Algal gums and mucilage’s constitute an abundant group of polysaccharides in plants.