• classify and identify foods that are major sources of monosaccharides, disaccharides, oligosaccharides, and polysaccharides in foods.
• generalize the role(s) of each major category of carbohydrates in foods.

Carbohydrates are generally made up of monosaccharides, disaccharides, oligosaccharides, and polysaccharides. In these categories, the actual chemical structure is represented a number of different ways. However, the basic formula is shown as:

are not carbohydrates, whereas

rhamnose (C6H12)5 is a carbohydrate

Regardless of their category, a carbohydrate has carbon, hydrogen and oxygen in the form of the following saccharose structure:

Why is an understanding of structure important? It is because the molecular components, functional groups, structure and conformation will influence the functional properties of foods. It will influence the way the food behaves under different production, processing and preparation stresses.

If one looks at the following glycosyl structure, it becomes apparent that the characteristics are dependent upon the basic structure:

As noted above, each glycosyl unit has several points of hydrogen bonding. In a glucan there are five oxygens per chain unit that can form hydrogen bonds. Note also the many hydroxyl hydrogens or oxygens which can potentially bond to a water molecule. These hydroxyl groups enhance the "water solubility" of the entire unit. In polysaccharides, the solubility is decreased due to the conformation of the polymer, itself, and the decreased access of these hydrophilic groups.

Just where do we find carbohydrates?

NAME/ CLASSIFICATION	ENDPRODUCTS HYDROLYSIS	BASIC STRUCTURE OF FORMULA	SOURCE, FUNCTION OR CHARACTERISTICS
MONO- SACCHARIDES: HEXOSES
Glucose	glucose		fruits, honey, corn syrup
Fructose	fructose		fruits, honey, corn syrup
Galactose	galactose		does not occur in free form in foods
Mannose	mannose		does not occur in free form in foods
MONO- SACCHARIDES PENTOSES
Ribose	ribose		derived from pentoses of fruits and nucleic acids of meat products & seafood, does not occur in free forms in foods, is an aldose
Xylose	xylose		is an aldose
Arabinose	arabinose		is an aldose

NAME/ CLASSIFICATION	ENDPRODUCTS HYDROLYSIS	BASIC STRUCTURE OF FORMULA	SOURCE, FUNCTION OR CHARACTERISTICS
DISACCHARIDES
sucrose	glucose fructose		beet and cane sugars, molasses, maple syrup, comes in many crystal sizes and grades
lactose	glucose galactose		milk and milk products
maltose	glucose		malt products, low concentrations in plants and processed foods

NAME/ CLASSIFICATION	ENDPRODUCTS HYDROLYSIS	BASIC STRUCTURE OF FORMULA	SOURCE, FUNCTION OR CHARACTERISTICS
POLYSACCHA- RIDES
starch	glucose		branches [amylopectin] contributed viscosity; linear[amylose] contributes gelling when gelatinized; granule is important to viscosity and gel formation
dextrins	glucose		usually considered to be hydrolysis products of incompletely broken down starch fractions
glycogen	glucose	N	meat products and seafood
cellulose	glucose		comprises skeletal structure of plant cell. Indigestible stable cell structural framework of stalks and leaves of vegetables, fruits and coverings of seeds.
hemicellulose	glucose		comprises some of the plant skeletal structure; amorphous heterogeneous substance; pentose and uronic acid predominant
pectic substances	galactose		cell cementing compound; fruits and vegetables; pectin will form gel with appropriate concentration, amount of sugar and pH. Amorphous substances in the matrix of plant skeletal structure; contains minor amounts of neutral monomers such as arabinose, amylose, galactose, mannose
Malin	fructose		matrix
Galactogens	galactose		monomers such as arabinose, xylose, mannose, raffinose
Mannosans	mannose
Raffinose	glucose fructose galactose
Pentosans	pentoses	Basic monomer structure

Although the following listing indicates possible role(s) of carbohydrates, it is not easy to define these in simple systems, let alone complex food systems. For example, in lollipops the sugars, glucose and/or glucose and fructose, will control crystallization. They will also contribute to the structure due to the sugar, sucrose, and serve as a flavor enhancer and sweetener due to all three sugars. In a more complex system such as a pineapple upside down cake, carbohydrates play many roles due to the presence of all categories of carbohydrates. Following is a listing of possible roles:

• agar: Agar is a polysaccharide found in the cell walls of some red algae and is unusual in containing sulfated galactose monomers. It requires nothing but extraction and purification to become agar, but is sometimes chemically modified into agarose for special applications. Agar: gracilaria or gelidium, is the queen of gelling agents. Laminaria has various oddball polysaccharides like laminarin (a storage polysaccharide) and alginic acid (from cell walls). They are chemically different from agar and, to my knowledge, not widely used.
• altrose: an artificially obtained sugar represented by C6H12O6
• amorphous: has no crystalline structure. Amorphous candy are those such as lollipops, marshmallows, caramels.
• amylase: an enzyme that hydrolyzes starch to produce dextrins, maltose, and glucose
• anhydrous: a solid containing no water bound to the molecule as in a hydrate or not water of crystallization.
• aspartame: is a low-calorie sweetener used in a variety of foods and beverages and as a tabletop sweetener. It is about 200 times sweeter than sugar. Aspartame is made by joining two protein components, aspartic acid and phenylalanine.
• beet sugar: is sugar [sucrose] processed from the sugar beet plant.
• beta-amylase: an enzyme that hydrolyzes starch by breaking off two glucose units at a time, thus producing maltose
• calorie: is the amount of energy required to raise the temperature of one milliliter (ml) of water at a standard initial temperature by one degree centigrade (C).
• cane sugar: is a sugar [sucrose] product processed from sugarcane.
• caramel: is a burnt sugar syrup used for flavor and color
• carmelization:sucrose heated past the molten point so that it dehydrates and decomposes; the development of brown color and caramel flavor as dry sugar is heated to a high temperature; chemical decomposition occurs in the sugar.
  is when sugar is melted, dehydrated and the products combine to give a characteristic caramel color and flavorful compounds.
• carbohydrate:are organic compounds that consist of carbon, hydrogen and oxygen. They vary from simple sugars containing from three to seven carbon atoms to very complex polymers. Only the hexoses (sugars with six carbon atoms) and pentoses (sugars with five carbon atoms) and their polymers play important roles in nutrition. Carbohydrates in food provide 4 calories per gram. Plants manufacture and store carbohydrates as their chief source of energy. The glucose synthesized in the leaves of plants is used as the basis for more complex forms of carbohydrates. Classification of carbohydrates relates to their structural core of simple sugars, saccharides. Principal monosaccharides that occur in food are glucose and fructose. Three common disaccharides are sucrose, maltose and lactose. Polysaccharides of interest in nutrition include starch, dextrin, glycogen and cellulose.
• catalyst: a substance that changes the rate of a chemical reaction without being used up in the reaction; enzymes are catalysts
• catalyze: to make a reaction occur at a more rapid rate by the addition of a substance, called a catalyst which itself undergoes no permanent chemical change
• clarifier: is a material or piece of equipment which will remove suspended solids or colloidal materials from a liquid.
• colloidal dispersion: state of subdivision of dispersed particles; intermediate between very small particles in true solution and large particles in suspensior; usually refers to the state of subdivision of dispersed particles; intermediate between very small particles in true solution and large particles in suspension
• color: is an orangey flavoring mixture kept close at hand in Peruvian kitchens, made with oil, garlic, and paprika. Sometimes is spicy hot with Aji peppers.
  is the property of a mateial in which specific visual wavelengths of the electromagnetic spectrum are absorbed and/or reflected.
• complex carbohydrates: carbohydrates made up of many small sugar units joined together, for example, starch and cellulose
• crystalline: the aggregation of molecules of a substance in a set, ordered pattern, forming individual crystals. Crystalline candy generally has sugar crystals.
• crystallization: the formation of crystals from the solidification of dispersed elements in a precise orderly structure.
• crystallize: is to coat and impregnate (fruit or petals) with sugar as a means of preserving them: a box of crystallized fruits. the formation of crystals from the solidification of dispersed elements in a precise orderly structure.
• cyclamate: A sweetener which is 30 times sweeter than sucrose, calorie free and heat stable and works synergistically with other sweeteners. It is approved for tabletop use in Canada and more than 50 countries in Europe, Asia, South America and Africa. Since 1970, however, the use of cyclamate has been banned in the United States on the basis of a study that suggested that cyclamates may be related to the development of bladder tumors in rats. Although 75 subsequent studies have failed to show that cyclamate is carcinogenic, the sweetener has yet to be reapproved for use in the United States.
  any group of non-nutritive sweeteners with general formula C6H11NHSO4H. is an artificial sweetener.
• dextrins: Mixture of soluble compounds formed by partial breakdown of starch by heat, acid or enzymes (complete breakdown yields maltose). Formed when bread is toasted. Nutritionally equivalent to starch; industrially used as adhesives in the sizing of paper and textiles, and as gums.
• disaccharide: sugars composed of two monosaccharide molecules combined, with the elimination of a molecule of water. For example, glucose, C6H12O6, plus fructose, C6H12O6, produces sucrose C12H22O11. Conversely, when a disaccharide is hydrolyzed, either by acid or enzymatically, a molecule of water is added and two monosaccharides result. Also known as dioses or disaccharoses.
• enzyme: Catalyst produced by living cells. Composed of protein and destroyed by heat and protein coagulation; responsible for most of reactions carried out in living tissues. Some are composed of two parts: the apoenzyme, the protein which is inactive alone; and its prosthetic group, a small non-protein molecule normally derived from a vitamin. This differs from a coenzyme, which readily dissociates from the enzyme protein (e.g. pyridoxal phosphate, biotin, thiamin pyrophosphate), while a prosthetic group is covalently bound (e.g. flavin mononucleotide and flavin adenine dinucleotide).
• enzymatic reactions: those that are catalyzed by enzymes, which are special proteins produced by living cells; a catalyst changes the rate of a reaction without itself undergoing permanent change.
• ester: a special linkage involving an alcohol and an organic acid.:
• Fahrenheit: a thermometer scale in which the freezing point of water is 32C and the boiling point is 212C.
• fermentation: Anaerobic metabolism. Used generally of alcohol fermentation of sugars, also production of lactic acid, citric acid, etc., by micro-organisms.
  the transformation of organic molecules into smaller ones by the action of microorganisms; for example, yeast ferments glucose to carbon dioxide and alcohol. The products are used for "esthetics" in beverages and leavening in selected baked products such as bread and rolls.
• fiber indigestible substances: including cellulose, hemicelluloses, and pectin (all polysaccharides), and also lignin, which is a noncarbohydrate material found particularly in woody parts of a vegetable
• galacturonic acid: a chemical molecule very similar to the sugar galactose and containing an organic acid (carboxyl) group in its chemical structure; a derivative of the sugar galactose, with an organic acid group
• gel: a colloidal dispersion that shows some rigidity and will, when unmolded, keep the shape of the container in which it had been placed; a semi-rigid structure at room temperature. This dispersion does show some rigidity or moldability.
• gelatinization of starch:the sum of changes that occur in the first stages of heating starch granules in a moist environment; includes swelling of granules as water is absorbed and disruption of the organized granule structure.
  the swelling of starch granules when heated in the presence of water
• gelation: a colloidal dispersion that shows some rigidity and will, when unmolded, keep the shape of the container in which it had been placed; a semi-rigid structure at room temperature. This dispersion does show some rigidity or moldability.
• gras list: the list of food additives that are "generally recognized as safe" by a panel of experts; this list is maintained and periodically reevaluated by the fda
• hexose: a simple sugar or monosaccharide with six carbon atoms
• hydration capacity: the ability of a substance, such as flour, to absorb water
• hydrocolloid: a substance with particles of colloidal size that is greatly attracted to water and absorbs it readily; colloidal materials such as vegetable gums, that bind water and have thickening and/or gelling properties; large molecules, such as those that make up vegetable gums, that form colloidal dispersions, hold water, and often serve as thickeners and stabilizers in processed foods
• hydrogen bond: the relatively weak chemical bond that forms between a hydrogen atom and another atom with a slight negative charge, such as an oxygen or a nitrogen atom; each atom in this case is already covalently bonded to other atoms in the molecule of which it is part.
• hydrolysis: a chemical reaction in which a linkage between subunits of a large molecule is broken; a molecule of water enters the reaction and becomes part of the end products
• hydrolyze: to glucose, C6H12)6, and fructose, C6H12O6; proteins are hydrolyzed to amino acids. Acid or alkali is usually needed as catalyst. to break a molecular linkage utilizing a molecule of water; to break chemical linkages, by the addition of water, to yield smaller molecules
• hygroscopic: Readily absorbing water, as when table salt becomes damp. Materials such as calcium chloride and silica gel absorb water so readily that they are used as drying agents.
• invert sugar: Mixture of glucose and fructose produced by hydrolysis of sucrose. 130% sweetness of sucrose. Important in the manufacture of sugar confectionery, since the presence of 10-15% of invert sugar prevents the crystallization of cane sugar.
• inversion reaction: is the reaction of the hydrolysis of sucrose to yield an equal mixture of glucose and fructose.
• invertase: Enzyme that splits sucrose into the invert sugars, glucose and fructose. Also known as sucrase or saccharase. Saccharases are widely distributed in plant tissues and the digestive juice of animals, and are of two types, glucosaccharases (in animals and the mould Aspergillus) and fructosaccharases (in yeast). They respectively, attack the glucose and the fructose end of complex sugars.
• maillard reaction: Two processes in foods can produce a brown color. One is the enzymatic oxidation of phenolic substances, such as occurs at the cut surface of an apple. The other is a reaction between proteins or amino acids and sugars, and is variously known as the Maillard reaction, the browning reaction and non-enzymic browning. It takes place on heating or on prolonged storage and is one of the deteriorative processes that take place in stored foods. It is accompanied by a loss in nutritive value, since the part of the protein that reacts with the sugar is the free amino part of the lysine. This complex is not digested and there is thus a reduction in the biologically available lysine.
• monosaccharide: group name of the simplest sugars, including those composed of 3 carbon atoms (trioses), 4 (tetroses), 5 (pentoses), 6 (hexoses) and 7 (heptoses). Also known as monoses or monosaccharoses.
• non-reducing end: in a polysaccharide or oligosacchride is the end which does not have a reducing agent. It lacks a free glycosidic hydroxyl.
• >nonnutritive sweetener: Sugar substitutes that contain no calories. Saccharin and cyclamates are examples.
• oligosaccharide: the general term for sugars composed of a few-often between three and ten-simple sugars or monosaccharides; a charbohydrate containing 2-20 sugar residues (the upper limit is not well-defined); intermediate-size molecules containing approximately ten or fewer basic units
• oxidation: a chemical change that involves the addition of oxygen; for example polyphenols are oxidized to produce different flavor and color compounds; a chemical reaction in which oxygen is added; addition of oxygen to carotenoid pigments lightens the color; chemical reactions in which oxygen is added or hydrogen is removed or electrons are lost; gain in oxygen or loss of electrons
• pectic enzymes: enzymes such as pectinase that hydrolyze the large pectin molecules
• pectin: is a gum which is water soluble pectinic acid of varying methyl ester content and degree of neutralization. It is obtained from citrus peel and apple pomace. It forms a gel in systems of low pH (pH 2.8-3.7) and high sugar (55-80%) levels. The gel sets at 55-99C and melts above 70C. Pectins are characterized by rapid and slow set types. the high methoxyl pectins have a degree of methylation (DM) greater than 50% while those of less than 50% degree of methylation are termed low methoxyl pectins. The low methoxyl pectins gel in the presence of calcium ions and do not require a certain level of acid or sugar. It is used in beverages at 0.1 - 0.2%, in jams and jellies at 0.1-0.4% and in confectioner jelly at 0.8 - 1.5%.
• pectin esterase: an enzyme that catalyzes the hydrolysis of a methyl ester group from the large pectin molecule, producing pectic acid; pectic acid tends to form insoluble salts with such ions as calcium (ca2+);these insoluble salts cause the cloud in orange juice to become destablized and settle
• pectinase: an enzyme that hydrolyzes the linkages that hold the small building blocks of galacturonic acid together in the pectic substances, producing smaller molecules
• pH: is a numerical scale from 1 to 14 indicating the degree of acidity; 1 is most acid; 7 is neutral; and 14 is most alkaline.
• phenylketonuria: Inherited metabolic defect wherein the essential amino acid, phenylalanine, is incompletely metabolized and the end-product, phenylpyruvic acid, is excreted in the urine. The product affects the brain and causes imbecility. The effect can be moderated by strict limitation of the phenylalanine intake.
• polar materials: chemical molecules that have electric charges (positive or negative) and tend to be soluble in water; having two opposite natures, such as both positive and negative charges
• polydextrose: a bulking agent made from an 89:10:1 mixture of glucose, sorbitol, and citric acid; in body metabolism it yields one kilocalorie per gram; often used with nonnutritive sweeteners in manufactured foods; is a condensation polymer of dextrose with minor amounts of sorbitol and citric acid; it contains only 1 kilocalorie per gram.
• polymer: a giant molecule formed from smaller molecules that are chemically linked together.
• polymerization: the formation of large molecules by combining smaller chemical units
• polysaccharide: Complex carbohydrates formed by the condensation of large numbers of monosaccharide units, e.g. starch, glycogen, cellulose, dextrin's, inulin. On hydrolysis the simple sugar is liberated.
• reducing end: is the end of a polysaccharide or oligosaccharide chain which contains a free glycosidic hydroxyl, and thus acts as a reducing agent.
  There can only be one reducing end per molecule.
• reducing sugar: Sugars that contain the aldehydic or ketonic reducing group, e.g. glucose, fructose, lactose, pentoses. They are tested for by their ability to reduce reagents such as Fehling's, Benedict's.
• reduction reactions: chemical reactions in which there is a gain in hydrogen or in electrons
• retrogradation: the process in which starch molecules, particularly the amylose fraction, reassociate or bond together in an ordered structure after disruption by gelatinization; ultimately a crystalline order appears
• roux: a mixture of butter and flour cooked together and used as a thickener in sauces
  thickening agent made by heating a blend of fat and flour
• slurry: a thin mixture of water and a fine insoluble material such as flour
• sol a liquid like colloidal system such as a stirred custard.
• solubility: is the amount and ease of solubility of solute in the solvent.
• solute: a dissolved or dispersed substance.
• solution: a mixture resulting from the dispersion of small molecules or ions (called the solute) in a liquid such as water (called the solvent).
• solution ions: or small molecules, called the solute, dispersed in a liquid, called the solvent
• solvent: a liquid in which other substances may be dissolved.
• starch: Starch is stored by plants and is taken from grains of wheat, potatoes, rice, corn, beans, and many other vegetable foods. Insoluble in cold water or alcohol but soluble in boiling water. Comparatively resistant to naturally occurring enzymes and this is the reason processors "modify" starch to make it more digestible. Starch is modified with propylene oxide, succinic anhydride, 1-octenyl succinic anhydride, aluminum sulfate, or sodium hydroxide. Used internally as a gruel in diarrhea and externally to soothe skin rashes; used in dusting powder as a demulcent for irritated colon and an antidote for iodine poisoning. Modified starches are on the FDA list for further study for safety. GRAS ACCEPTABLE for packaging.
• starch granule: a particle formation starch is stored; composed of millions of starch molecules laid down in a very organized patter; the shape of the granule is typical for each species; starch molecules are organized into tight little bundles, called granules, as they are stored in the seeds or roots of plants, the granules with characteristic shapes and sizes, can be seen under the microscope.
• sugar: is a sweet crystalline substance obtained from various plants, especially sugar cane and sugar beet, consisting essentially of sucrose, and used as a sweetener in food and drink. It is a lump or teaspoonful of sugar, used to sweeten tea or coffee. Sugar also means to sweeten, sprinkle, or coat with sugar.
• sweeteners: Sweeteners as a class can not be disregarded. Not all sweeteners are "sugars" or carbohydrates. t wonderful full flavored low calorie drink TAB no longer was the "greatest".
• syneresis: Oozing of liquid from gel when cut and allowed to stand (e.g. jelly or baked custard). the oozing of liquid from a rigid gel; sometimes called weeping
• synergism: an interaction in which the effect of the mixture is greater than the effect of the sum of component parts.
• total sugars:
• translucency: partial transparency; not opaque.
• tuber: an enlarged underground stem, for example, the potato.
• vapor pressure: the pressure produced over the surface of a liquid as a result of a change in some of the molecules from a liquid to a vapor or gaseous state.
• vegetable gums: polysaccharide substances that are derived from plants, including seaweed and various shrubs or trees, have the ability to hold water, and often act as thickeners, stabilizers, or gelling agents in various food products; for example, algin, carrageenan, and gum arabic.