Understanding Carbohydrates: Types, Formation, and Properties

1. CARBOHYDRATES

2. There Are 7 Major Categories of Nutrients: Carbohydrates Introducing Carbohydrates Fiber Proteins Fats Minerals Vitamins Water

3. What are carbohydrates?... A carbohydrate is an organic compound that is the body’s main source of energy. If you break down the word ‘carbohydrate’, you’ll find part of the names of its main components: carbon and hydrogen. A carbohydrate molecule also includes oxygen. Sugar Simple carbohydrates consist of one or two sugars, found in very small molecules. Starches are complex carbohydrates, which are very large molecules made out of many simple carbohydrate units. Starch 1 hydrogen and 1 oxygen atom bonded to the rest of the molecule is called a hydroxyl group.

4. How carbohydrates form... Using the sun’s energy and the green pigment in plants called chlorophyll, plants convert carbon dioxide and water into glucose and oxygen. Glucose is the basic sugar molecule from which all carbohydrates (sugars, starches, and fiber) are made.

5. Sugars are simple carbohydrates... A ‘saccharide’ is simply a sugar or a substance made from sugar. They are classified as ‘monosaccharides’ (simple sugars including glucose) or ‘disaccharides’ (two monosaccharides bonded together). Granulated sugar (table sugar), brown sugar, and confectioners sugar (powdered sugar) are made from sugar cane or sugar beets. These are examples of the disaccharide sucrose. Maltose, the sugar from grains, and lactose, the sugar from milk, are also disaccharides. The monosaccharide fructose is found in fruit; glucose is found in corn syrup, honey, and tree sap (maple syrup).

6. Properties of sugar: sweetness... Some sugars are sweeter than others. In taste tests of pure sugars, fructose is the sweetest, and then decreasing in order of sweetness is sucrose, glucose, maltose, and finally lactose. Factors such as concentration, consistency, temperature, and pH level affect how sweetness is judged. For example, fructose seems sweeter when used in cold foods and in slightly acidic drinks. Sucrose seems sweeter when used in the same recipes as small amounts of salt. When this apple is baked, it needs brown sugar added. The fructose tastes less sweet when warm. This frosting calls for 2 pounds of powdered sugar (sucrose) and a pinch of salt. Salt makes the sugar taste ‘sweeter’.

7. Properties of sugar: carmelization... Carmelization is the browning reaction that can occur with any kind of sugar. It requires either a low (acidic) or high (alkaline) pH. As sugar is heated, its molecular structure is changed, and the new molecules with a higher concentration of carbon create the distinctive caramel color. Sugars differ in the degree to which they carmelize and the temperature at which they react. Sucrose and glucose carmelize at 170ºC (338 ºF), and fructose carmelizes at (230ºF). Onions carmelize when cooked slowly up to 230ºF; the process brings out the sweetness. Carmelized sugar for candy: 338ºF

8. Properties of sugar: solubility... Sugars are highly soluble in water because they contain many hydroxyl groups, which form hydrogen bonds with water molecules. The solubility of sugar increases as the temperature of the water rises. You can make a ‘supersaturated’ solution: Dissolve more sugar in water than would normally be possible…by heating the water, changing volume, and/ or adding pressure. Then, with absolutely no agitation, cool the solution. This is a ‘supersaturated’ solution. A carbonated beverage is a supersaturated solution of carbon dioxide gas in sugar water. Rock candy is made from a supersaturated solution of sugar and water.

9. Properties of sugar: crystallization... As you bring a sugar (solute) and water (solvent) solution (syrup) to a boil, the water begins to evaporate. This increases the concentration of the sugar in the water. When sugar reaches a specific concentration, crystallization occurs. Fudge, fondant, and penuche are crystalline candies. A candy-maker makes a syrup and must follow the recipe carefully, to keep the crystals very small. Smaller crystals produce the smooth and creamier texture. Peanut brittle, toffee, and hard candies are non-crystalline candies. Specific ingredients are added that ‘interfere’ with the crystallization process…such as corn syrup, lemon juice, cream of tartar, or butter.

10. Glucose converts to starches and fiber... A plant can convert simple glucose molecules into starches and fiber as the plant matures. That is why peas from a very young plant taste sweeter than those from an older plant. The fiber formed from the glucose molecules strengthens and supports the plant’s cell walls. The older the plant gets, the stronger or ‘tougher’ the fiber becomes. Very early or young ears of corn are sweet and tender; the longer they stay on the plant, the less sweet and chewier they become.

11. Starches are complex carbohydrates... In complex carbohydrates, from ten to several thousand glucose monosaccharides of the same kind chain together to form a single, large, starch molecule called a polysaccharide or polymer. The starches are stored in the plant, largely in the seeds (such as wheat, corn, rice kernels) and the roots (potatoes). Even though the starch chain is comprised of glucose molecules…the starch itself does not taste sweet. It is bland.

12. Starches have two structures... Starch molecules known as ‘amylose’ are linear, taking a long and narrow form like a line. Root starches are in the amylose form. Examples are potatoes or cassava root (the source of tapioca). Starch molecules known as ‘amylopectin’ have branches, like veins in a leaf. The cereal starches such as wheat, corn, and rice are in amylopectin form. Cassava root

13. Sources of starches... Pasta Cornmeal Wheat ,rye, barley Potatoes Beets, corn, parsnips, peas, acorn squash Oatmeal; cereals Rice

14. Properties of starches: gelatinization... Starches are NOT water soluble like sugars. The molecules are too big to form solutions. When starches are heated in water, an irreversible thickening process called gelatinization occurs. The starch granules absorb the water and swell. Hydrogen bonds form between the starch and water molecules, and a paste is formed. As gelatinization thickens a mixture, VISCOSITY increases. Viscosity is ‘resistance to flow’. The greater the concentration of starch, the more viscous a paste becomes.

15. Properties of starches: thickening... Amylopectin, because of its branched quality, does not mix with water as easily as amylose. Therefore, amylopectin does not thicken as easily and is a good type of starch for foods that always need to remain a bit runny… like ketchup and gravy. Amylose starches are used for foods that need to gel more firmly and permanently, like pudding. The temperature at which a paste forms varies with the type of starch. Wheat starch thickens at a lower temperature than cornstarch.

16. Properties of starches: retrogradation and syneresis... When starch pastes cool without stirring (especially in the refrigerator), they change to gels, and lose the ‘flow’ properties they formerly had. After a period of time, however, the molecules shift and form a somewhat ‘gritty’ texture. This is called RETROGRADATION. During retrogradation, a mixture may ‘weep’. Water leaks from the gel as it ages. This is called SYNERESIS  (sĭ-nĕr'ĭ-sĭs). The starch molecules pull together more tightly, the gel network shrinks, and the water is pushed out of the gel. You can see liquid forming on the surface.

17. Carbohydrates provide energy... Carbohydrates are one of three macronutrients that provide the body with energy, along with protein and fats. In order for the body to use carbohydrates for energy, food must undergo digestion, absorption, and glycolysis. It is recommended that 55 to 60 percent of caloric intake come from carbohydrates.

18. Digesting carbohydrates... Carbohydrates must be digested and absorbed in order to transform them into energy that can be used by the body. Food preparation often aids in the digestion process. When starches are heated, they swell and become easier for the body to break down. In the mouth the enzyme amylase, in saliva, mixes with food products and breaks some starches into smaller units. However, once the carbohydrates reach the acidic environment of the stomach, the amylase is inactivated. After the carbohydrates have passed through the stomach and into the small intestine, key digestive enzymes are secreted from the pancreas and the small intestine where most digestion occurs and the energy is released.

19. Step 1 of the metabolic process... Remember step 1 of this metabolic process? Glycolysis, or splitting the glucose (sugars and starches) molecules in half releases the energy. glycolysis Enzymes are proteins, synthesized in cells. They act as catalysts, causing all the body's chemical processes to take place quickly and completely. Enzyme The enzymes that break down the glucose molecules have names like ‘sucrase’, ‘invertase’, ‘lactase’. Energy They break the glucose molecule in half, forming two 3-carbon molecules. These molecules are called pyruvic acid or pyruvate. This process is called glycolysis and occurs in the cytoplasm of the cell. A small amount of energy is released during this process, as the bonds within the molecule are broken. This is a CATABOLIC reaction. Black spheres are carbon atoms, white are hydrogen, and red are oxygen.

20. How fast are carbohydrates metabolized? To digest and metabolize a simple sugar such as glucose may take less than 30 minutes. Because juice would be quickly digested, it may be one of the quickest to process. The release of energy would be quick…but brief! The more complex structure of starches may require as much as 2-4 hours to digest and metabolize. The release of energy would be slower, but last over a longer period of time.

21. Glucose is absorbed into the bloodstream... After digestion, when the starches and simple sugars are broken back down into glucose molecules, and after glycolysis that releases catabolic energy… the glucose is transported to the liver. Some of it is stored in the liver. Some is sent to muscles and organs that require energy. If there is too much, it can be converted to and stored as fat. The glucose in the bloodstream is called ‘blood sugar’ or ‘dextrose’. As one of its digestive duties, the pancreas monitors the flow of glucose to the cells and secretes the hormone ‘insulin’. Insulin keeps the glucose in the blood at a normal level. If blood sugar is too high, insulin triggers the liver to remove sugar and store it as glycogen. When blood sugar levels are too low, the glycogen is changed back into glucose and released into the blood.

22. Blood sugar and diabetes... Diabetes (dī'ə-bē'tĭs, -tēz)is a condition in which the body cannot regulate blood glucose levels. In Type I diabetes that affects children and young adults, the pancreas secretes little or no insulin. In the more common Type II diabetes that can affect people of all ages, the pancreas does produce insulin, but either not enough or the insulin isn’t used effectively. Both types of diabetes cause abnormally high blood sugar levels that can strain and damage the heart and kidneys. This high blood sugar level is called ‘hyperglycemia’. The kidneys filter some of the glucose and excrete it in the urine; very little actually reaches the cells. Blood sugar levels consistently above 150 mg. are indicative of hyperglycemia. The diabetic monitors their own blood sugar levels, injecting insulin when levels are high and eating carbohydrates when levels are low.

23. Hypoglycemia... An abnormally LOW level of blood sugar is called ‘hypoglycemia’. There are several causes of this condition. If it occurs for a diabetic, it may be a reaction to an insulin injection. In some cases, it appears to be associated with malfunctions or diseases of the liver, pituitary, adrenals, liver, or pancreas. It sometimes happens after long periods without food, and occasionally following strenuous exercise. Other factors sometimes associated with hypoglycemia include: pregnancy , a weakened immune system, a poor diet, prolonged use of drugs including antibiotics, chronic physical or mental stress, heartbeat irregularities, allergies, breast cancer, high blood pressure treated with some medications, and upper gastrointestinal tract surgery. Blood sugar levels consistently below 70mg. are indicative of hypoglycemia.

24. Ketosis... It is important to consume a minimum amount of carbohydrates to prevent ketosis, a condition resulting from the breakdown of fat or muscle protein for energy in the absence of carbohydrates. Ketosis can occur in previously healthy people during prolonged fasting or starvation, after persistent vomiting, or on a very high fat and low carbohydrate diet; or it can occur because of disordered hormonal control of metabolism in diabetes. The high rate of breakdown of fatty acids by the liver produces the ‘ketone bodies’ (acetoacetate and b-hydroxybutyrate) which are released into the blood and alter normal pH balance (this is particularly harmful to an unborn fetus). Some of the acetoacetate is converted to acetone — another ‘ketone body’ — mainly in the lungs, and this becomes noticeable on the breath. The breath smells like nail polish remover.

25. Recommended daily allowance... No RDA for carbohydrates has been set, but a minimum of 50-100 grams should be consumed daily for normal brain function. Carbohydrates should make up 55% of your daily total caloric intake. Sugars and starches that occur naturally in foods is preferred over those that are ‘added’ to foods, such as refined sugars. Foods from the fruits, vegetables, and breads & cereals group on the food pyramid provide carbohydrates. The 2005 Dietary Guidelines for Americans recommends no more than 8 teaspoons per day of added sugar based on a 2,000 calorie/day diet.  That's 32 grams if you're reading labels. 8 teaspoons x 4 grams per teaspoon = 32 total grams sugarWith 40 grams in a can, a single non-diet Coke provides 10 teaspoons of sugar.

26. Sugar substitutes... A sugar substitute is a food additive that duplicates the effect of sugar or corn syrup in taste, but usually has less or no food energy (calories). Some sugar substitutes are natural and some are synthetic or artificial sweeteners. Artificial sweeteners cost the food industry only a fraction of the cost of natural sweeteners. There is a great deal of controversy about the use of sweeteners, including discussions on the increased preference for sugary foods and cancer concerns. They are, however, low or free from calories and do not contribute to dental decay like regular, refined sugars. Artificial sweeteners include saccharin (săk'ər-ĭn), aspartame  (ăs'pər-tām‘), sucralose (sū'krə-lōs'), neotame (nē'ō - tām‘), acesulfame (ă-cē'sĭl-fām) potassium, and the herbal supplement called stevia (stē´vē-ă). Some have an aftertaste. Only sucralose retains its sweetness when heated. Two natural sugar substitutes derived from berries, fruit, vegetables, and mushrooms are sorbitol (sôr'bĭ--tŏl‘, -tōl') and xylitol  (zī'lĭ-tŏl, tōl')

27. High fructose corn syrup... High fructose corn syrup is the most commonly used sweetener in food manufacturing. The version of high-fructose corn syrup used in sodas and other sweetened drinks consists of 55 percent fructose and 45 percent glucose, very similar to refined white sugar, which is 50 percent fructose and 50 percent glucose. High-fructose corn syrup is found in many foods and beverages, including Coke and Pepsi, Snapple iced tea, Dannon yogurt, Chips Ahoy cookies, Ritz crackers, Wonder bread, Wishbone ranch dressing, and Campbell’s tomato soup. High-fructose corn syrup is artificial because it is not found anywhere in corn. Enzymes used in food manufacturing turn most of the glucose molecules in the corn into fructose, which makes the substance sweeter. The fructose is then combined with regular corn syrup (glucose). The final product is a clear, goopy liquid that is roughly as sweet (and calorie laden) as sugar.

28. Low-carb diets... Low-carb diets limit carbohydrates in order to lose weight (bread, grains, rice, starchy vegetables and fruit), and emphasize sources of protein and fat instead. Many types of low-carb diets exist, each with varying restrictions on the types and amounts of carbohydrates. Examples of low-carb diets include the Atkins diet, Zone diet, South Beach diet, Lifeplan, and Protein Power. Nov. 1999 High fat diets can contribute to heart disease. Excess protein can be hard on the kidneys. A calorie…is a calorie…and if you eat too many calories (no matter where they come from), you will gain weight.

29. The End CARBOHYDRATES