arbohydrates arbohydrates are the major components of plants, comprising 60 to 90% of their dry weight. They are produced by the process of photosynthesis in green leaves. Simple arbohydrates: The common small, or simple carbohydrates, are made of one (mono) or two (di) units. Glucose, galactose, and fructose are simple monosaccharides that combine to form disaccharides such as maltose, lactose, and sucrose. Examples of Monosaccharides: Formula Structure ommon Source Fructose 6126 In honey Glucose 6126 In fruits, vegetables, corn syrup
2 Examples of Disaccharides: Formula Sucrose 122211 Structure ommon Source In sugar cane and sugar beets Lactose 122211 In Milk omplex arbohydrates: The complex carbohydrates amylose, and cellulose are long chain polymers of the simple carbohydrate glucose. Examples of omplex arbohydrates: (Polysaccharides) Amylose: Polymer of -D-glucose ommon Source Starches: Rice, wheat, potatoes, beans ellulose: Polymer of β-d-glucose n n Plant Fibers: otton, wood, stems, leaves
3 Amylose, and its branched relative, amylopectin, are major components of starches, the energy storage carbohydrates found in tubers and edible roots. Amylose and amylopectin are polymers of D-glucose in which the anomeric carbon of each glucose unit is in the alpha ( ) form. ellulose is plant structure material like that of wood, stems, and leaves. The major function of cellulose for us is not as a source of glucose for energy, but rather as fiber to keep our digestive tract clean. ellulose is a polymer of D-glucose in which the anomeric carbon of each glucose unit is in the beta (β) form. Sweetness: Simple carbohydrates are called saccharides from the Latin term saccharum (sweet) because of their sweet taste. Many of the small carbohydrates, mono and disaccharides, are used as sweeteners. They fit into the taste receptor sites on our tongues and send the signal to our brains that we call sweet. Artificial sweeteners mimic the shape of the simple sugars and will fit into the same taste receptor sites that natural sugars do and so send to our brains a similar sweet signal. Artificial sweeteners are not metabolized in the same way as natural sugars. Sucralose Examples of Artificial Sweeteners: Formula 121911l3 Structure l l l ommon Source Splenda Aspartame 141852 utrasweet Equal 2 2 2 3 Saccharin 75S3 Sweet Low S
4 Solubility: Mono and Disaccharides are soluble in water since they have many exposed s along their surfaces which can easily hydrogen bond with water. Larger carbohydrates can still be soluble depending on the positioning of their s. If the s are abundant on the exterior of a carbohydrate (even a large one) then hydrogen bonding with water can occur and the carbohydrate can be made to dissolve in water. If, however, there is internal hydrogen bonding within a carbohydrate, or coiling that may prevent water from hydrogen bonding to the s, then the carbohydrate will not dissolve in water. Starch granules, tightly coiled strands of amylose and amylopectin, are not soluble in water at ordinary temperatures and so are convenient forms in which to store the plant s excess energy supplies. Roots and seeds are the organs in which starch is usually concentrated. Forms of amylose starch can be made to be soluble by heating in water so as to disrupt the solid packing of the strands. The coils unravel into long strands of amylose which have s more exposed to hydrogen bond with water. ot only are the uncoiled strands more water soluble but they can also tangle with each other to form gels. We often use these unraveled starch strands as thickeners in cooking or for stiffening fabrics. Although there are some forms of soluble fiber (like in oatmeal), most plant cellulose is not water soluble even with heating. ellulose strands have a lot of internal hydrogen bonding with themselves and each other. They form tight, twisted cables that make very strong structure material that does not unravel even in hot water. hemical Reactivity: olorization: Amylose, the unbranched chain polymer of -D-glucose in starch, coils into tight spirals. Elemental iodine, I2, which is normally yellow-brown in color, will fit inside the amylose coil and complex with the s inside the spiral. The resulting amylose-iodine complex is a deep blue-black color. Iodine, I2, is commonly used as a test for the presence of amylose starch. Legal U.S. dollar bills made from a linen fabric will not react with iodine; however, the mark of the iodine pen on bills made from starched paper will show the characteristic dark blue sign of a counterfeit.
5 ydrolysis: Each bond connecting monosaccharide units (the glycoside bond) can be broken by hydrolysis; the reaction with water in the presence of a catalyst. Disaccharides can thus be hydrolyzed into two monosaccharides. Polysaccharides can be hydrolyzed into shorter chains or further into simple sugars. In the laboratory we can catalyze sugar hydrolysis reactions with acid, or we can use catalytic enzymes that are specific for each carbohydrate. Sucrose is hydrolyzed into glucose and fructose by catalysis with the enzyme, sucrase. Maltose hydrolyses into glucose with maltase. Lactose hydrolyses into galactose and glucose with lactase. Amylose and amylopectin are easily hydrolyzed into shorter chains of glucose called dextrins which are then further hydrolyzed into the disaccharide maltose and then to glucose (blood sugar) itself. In our bodies the hydrolysis of starches in digestion is catalyzed by the enzymes amylase and maltase. People vary in the amount of amylase in their saliva or urine. The hydrolysis of cellulose can be catalyzed in the laboratory with acid or by the enzyme cellulase found in certain bacteria. The human body does not contain the enzyme cellulase and so cannot convert cellulose into glucose for use as an energy source. Therefore, the long chain of cellulose stays intact for use as fiber. xidation: Because of the abundance of hydroxyl groups, s, and aldehyde groups, =, simple carbohydrates are easily oxidized. The aldehyde groups of simple sugars can be oxidized to carboxylic acids using the oxidizing agent opper(ii) Sulfate, us4. Benedict s reagent, a basic solution of us4, is blue in color which is characteristic of many u 2+ compounds. When blue u 2+ causes the sugar aldehyde to oxidize it becomes reduced itself to u + which is brick red. A sugar that reduces blue u 2+ to brick-red u + is called a reducing sugar. Tests for reducing sugars are commonly performed in medicine to identify the simple sugars present in blood or urine that may be indicators of metabolic problems or disease. Dehydration: When carbohydrates are either heated or reacted with acid, s and s combine and leave as water,. As water molecules begin to escape the carbohydrate begins to turn yellow, then brown, and then eventually black.
6 As paper (a cellulose product processed with acid) ages it slowly dehydrates and turns yellow. Scrap-bookers prefer acid-free paper that will stay white longer. aramel candy is sugar that has been heated so as to partially dehydrate. Loss of some of the s from sugars results in a caramel brown color and also gives the characteristic taste of browned carbohydrates. A common method for making sauces and gravies uses the formation of a roux. Flour or starch is heated in oil until it browns. Water or milk is then added and the mixture heated to a thick sauce. The word roux is French for red and at some point in history came to mean flour that had been cooked long enough to change color. The fat and flour undergo browning reactions when cooked giving flavorful dehydrated molecules in much the same way as the caramelization process. The more the flour is browned the less power it has to thicken since some of the starch molecules shorten as well as dehydrate in the heating process. Therefore, more of a dark brown roux is needed to thicken a given amount of liquid than if using a pale roux. If all of the s on a carbohydrate are removed as water then all that remains of the compound is black carbon charcoal. This phenomenon is observed when food or wood is burned to blackness. sazone Formation: When a monosaccharide is in its open chain form, its aldehyde or ketone group is free to undergo the usual reaction of such groups with various substituted hydrazines. If glucose is treated with phenylhydrazine, a phenylhydrazone is formed. If excess phenylhydrazine is present, the alcohol group on the carbon adjacent to the carbonyl group is oxidized, and the resulting ketone reacts to form a second phenylhydrazone, which results in the formation of an osazone. Under a standard set of conditions, the time of formation of an osazone from a sugar is characteristic of that sugar. + 2 glucose phenylhydrazine 2 "osazone"
7 Procedures: I. Sweetness: 1. Taste a small sample of each sugar or sweetener available and rank them in order of sweetness. ( # 1 being the sweetest.) 2. n the report sheet, record the predicted order of sweetness from your textbook. ompare your taste results with the predicted order (see table on page 10) and report your observations. II. Solubility: 1. btain 3 stoppered test tubes. Into tube # 1 put a corn kernel sized scoop of glucose (a monosaccharide). Into tube # 2 put a corn kernel sized scoop of sucrose (a disaccharide). Into tube # 3 put a corn kernel scoop of corn starch (a polysaccharide). 2. To each tube add about 5 mls water. Stopper and shake each tube to mix. Record the solubility of each (S = soluble, I = insoluble, and PS = only partially soluble) on the report sheet. 3. If any of the samples are not completely soluble in cold water, warm their test tubes in a beaker of boiling water. Record the solubility of each. 4. Save these samples for the olorization of Iodine test (Part III). III. hemical Reactivity: A. olorization of Iodine, I 2 : Test for Starch: 1. Take the 3 samples you used to test for solubility and number them ( # 1 glucose, # 2 sucrose, & # 3 starch) 2. btain 2 more test tubes. Into 1 of these put about 5 mls water to use as the control sample. Label this tube # 0 and put it first in your line up of sugar samples. 3. Into the other clean test tube spit enough saliva to measure about 1 inch. Label this tube # 4. 4. Add 1 drop of Iodine, Potassium Iodide (I2, KI) solution to each of the test tubes. bserve and record the color of all samples. 5. Take 5 drops of the contents of tube # 3 (the corn starch) and drop it into the saliva, tube # 4. Shake to mix.
8 6. Set tubes # 3 and # 4 aside. heck them every 20 minutes or so. bserve and record any color changes. (ot all people have the same amount of amylase in their saliva. heck the samples of other class members to see how their amylase reacted) B. xidation: 1. Set up a boiling water bath by filling your largest beaker ¼ full of water and heating it on a hot plate. 2. btain 6 clean test tubes with stoppers labeled # 1- # 6. Put about 2 mls water into each. 3. Leave tube # 1 as the control sample. Into tube # 2 put a pea sized scoop of fructose. Into tube # 3 put a pea sized scoop of glucose. Into tube # 4 put a pea sized scoop of sucrose. Into tube # 5 put a pea sized scoop of lactose. Into tube # 6 put a pea sized scoop of corn starch. Shake each tube to thoroughly mix the solutions. 4. Into each tube add 3 ml of Benedict s reagent. Stopper and shake each to mix. 5. Place all 6 tubes into the boiling water bath at the same time with the stoppers on very loosely so they do not pop off during heating. Remove the tubes after 5 minutes and record any color changes. 6. n the report sheet, label each sample as reducing or nonreducing. 7. Report any discrepancies in your results. Did each sample give you the results expected? Explain any anomalies.. Dehydration with eat; aramelization: 1. Into your largest beaker pour about 10 mls sucrose. 2. bserve the color, odor, chemical changes, etc. as you heat the sucrose over a hot plate while stirring constantly (or the sugar will burn). Stop heating when the sugar starts to turn caramel brown. Record all observations on your report sheet. 3. Return the beaker of caramel to the hot plate to continue the dehydration just until you have observed that the sugar is turning black. Remove from heat.
9 4. lean the beaker by boiling hot tap water in it until the burnt sugar is dissolved enough to be washed out. D. Dehydration with Acid: 1. Into a 50 ml beaker pour about 25 mls sucrose (half full). 2. Move the beaker of sucrose to the fume hood. Pour 10 mls concentrated Sulfuric Acid (this acid is very dangerous!) onto the sucrose and observe the color, odor, and chemical changes. Record all observations. 3. Place a drop of concentrated Sulfuric Acid on a piece of paper towel. Record your observations. IV. PRATIAL APPLIATIS I KIG: A. Preparation of Gravy: ornstarch method 1. Mix completely 2 level Tablespoons of cornstarch with 1.5 teaspoons (7.5 mls) of water in a small beaker. Play with the results of this Gak and describe its texture on the report sheet. 2. In a separate beaker, heat ½ cup (120 mls) of water (or broth). 3. With constant stirring, pour the corn starch gak into the hot water and bring to a boil for 1 minute or until smooth and bubbly. 4. Describe your results on the report sheet. B. At ome Preparation of a heese Sauce: Roux method 1. Melt 2 level Tablespoons of shortening or margarine in a beaker over low heat stirring constantly. 2. Blend in 2 level Tablespoons of flour (and seasonings like salt, pepper, or dry mustard if making a real cheese sauce) and cook over low heat, stirring until mixture is smooth and bubbly. The flour will brown as the amylose dehydrates. 3. Remove from heat. Stir in ½ cup (120 mls) water (milk for a real cheese sauce) then stirring constantly, bring to a boil for 1 minute or until smooth and bubbly. (If really making a cheese sauce; blend in ½ cup cheese, cut up or grated. Stir until cheese is melted.) 4. Describe your results on the report sheet. ompare this sauce made with four to that made with cornstarch.
10 Relative Sweetness of Sugars and Sugar Substitutes based on fructose = 100 Sugars Relative sweetness Sugar substitutes Relative sweetness Fructose 100 Invert Sugar 75 Sucrose 58 Glucose 43 Maltose 19 Sucralose (Splenda) Saccharin (Sweet Low) Acesulfame potassium (Sweet ne) Asparatame (Equal) Rebiana (Truvia, PureVia) 3.5 10 4 1.7 10 4 1.2 10 4 1.0 10 4 1.2 10 4 Galactose 19 eotame 4.1 10 5 Lactose 9.2 Stevia 3.0 10 4 Xylitol 58
11 ame Date arbohydrate Report: I. Sweetness. Rank in order of sweetness 1-8 ( # 1 being the most sweet) Fructose Glucose Sucrose Aspartame Splenda Saccharin Stevia Xylitol rder of Sweetness (Your Taste) rder of Sweetness (page 10) ompare your taste with table: II. Solubility: 1. Glucose 2. Sucrose 3. Starch (Amylose) Solubility (cold) Solubility (hot) III. hemical Reactivity: A. olorization of Iodine, I2: 0. ontrol 1. Glucose 2. Sucrose 3. Starch (Amylose) 4. Starch + Saliva (Amylose + Amylase) bservation (color) Immediate After 20 minutes onclusion (Is Amylose present? Yes or o) Immediate After 20 minutes
12 B. xidation 1. ontrol 2. Fructose 3. Glucose 4. Sucrose 5. Lactose 6. Starch olor after eating w/ Benedicts Sugar Type (circle one) Reducing or nonreducing Reducing or nonreducing Reducing or nonreducing Reducing or nonreducing Reducing or nonreducing Reducing or nonreducing. & D. Dehydration with eat and Acid: bservations for Each General Explanation for All eat on Sucrose What is happening in all of these cases and why? Acid on Sucrose Acid on ellulose (paper towel) IV. Practical Applications in ooking: bservations, Results, omments A1. Gak A2. Thickening B. At ome: heese Sauce bserve the results if you make this at home.