Carbohydrates

1. Carbohydrates Chapter 15

2. What Are Carbohydrates? • Carbohydrate = an organic compound that is the body’s main source of energy. • Made up of two main elements carbon and hydrogen • Carbohydrates are found mainly in foods from plant sources, such as fruits, vegetables, grain products, dry beans and peas • Carbohydrates consist of simple and complex carbohydrates • Simple carbohydrates consist of one or two sugars in very small molecules • Complex carbohydrates, which are starches and fiber, are very large molecules

3. How Carbohydrates Form • Carbohydrates are produced by green plants. • Using the sun’s energy, plants convert carbon dioxide and water into glucose and oxygen. The carbon dioxide comes from the air, and water is taken up by a plant’s roots, known as photosynthesis. • The green pigment for photosynthesis to occur is called chlorophyll. • Glucose = basic sugar molecule from which all other carbohydrates are built • A plant can convert glucose molecules into other sugars, starches, and fiber. • It usually starts by changing glucose into other sugars, these become starches. • Green peas from a young plant taste sweeter, than peas from an older one because they are high in simple carbohydrates, or sugar. • Peas from an older plant contain a higher level of starch

4. Simple Carbohydrates: Sugars • Simple carbohydrates or sugars, are a natural part of many food. • Ex. Pineapple and oranges have a sweet taste • Foods with naturally occurring sugars often contain other nutrients too. Sugars can also be extracted from plants and used to sweeten food. • The basic sugar molecule is a six-sided ring made of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. • Hydroxyl group = combination of hydrogen and oxygen, containing one atom of each element. • Saccharide = is simply a sugar or a substance made from sugar. (sugars have the following 2 basic molecular structure) • Monosaccharide (single sugars) – including glucose, the “building block” of all other sugars – (fructose, galactose – natural sugars found in food) • Disaccharides (sugars made up of 2 monosaccharide's bonded together) – include sucrose which is made up of glucose and fructose, lactose – found in milk composed of glucose and galactose, maltose occurs in cereals and sprouting grains

5. Properties of Sugar - Sweetness • Sugars differ in amount of sweetness • Fructose is generally found sweetest. • Sucrose, glucose, galactose, maltose, and lactose follow in decreasing order of sweetness • Honey is an example of a very sweet sugar – when bees make honey, they collect nectar from flowers that contain fructose, glucose and sucrose. An enzyme in their body converts most of the sucrose into fructose and glucose – this makes honey a highly concentrated solution of two of the sweetest sugars. • Hot and cold also affects the sweetness of sugar ex. Fructose is generally sweeter in cold foods

6. Properties of Sugar - Caramelization • Caramelization = the browning reaction that can occur with any kind of sugar • As sugar is heated, some of the water leaves its molecules in the form of hydrogen and oxygen. The new molecules have a higher concentration of carbon, creating the distinctive caramel color • Sucrose, galactose, and glucose all caramelize at 170°C. • Fructose on the other hand, caramelizes at 110°C

7. Properties of Sugar – Solubility (ability to dissolve) • Sugars are highly soluble in water • Fructose most soluble in water followed by: • Sucrose • Glucose • Glalactose • Maltose • Lactose • Water temperature affects solubility of sugar • 25°C the solubility of sucrose is 211g per 100g of water • However if you want to dissolve larger quantities of sugar, you need to increase the waters temperature • Supersaturated = the solution contains more dissolved solute than it would normally hold at that temperature. ( meaning add sugar to hot water, than cooling the water down, without stirring results in sugar water)

8. Properties of Sugar - Crystallization • Water evaporates, increasing the concentration of sugar in the solvent. When sugar reaches a certain concentration, crystallization occurs • Crystallization from a supersaturated solution begins when particles enter the solution (anything even dust) • The size of the crystals depends on how many particles are present and how quickly the crystals grow around them

9. Complex Carbohydrates: Starch and Fiber • When people talk about starch and fiber in the diet, they’re speaking of complex carbohydrates • Both are found in dry beans, peas and lentils, potatoes, corn, rice pasta and breads. • Simple carbohydrates have one or two monosaccharides per molecule • Complex carbohydrates, glucose forms compounds called polysaccharides. Polysaccharides is an example of a polymer • Polymer = large molecule formed when small molecules of the same kind chain together

10. Structure of Starches • Starches are literally plant food, starches are stored in granular form, largely in the seeds and roots • A single molecule of starch can include anywhere from 400 to several hundred thousand alpha-D-glucose (form of glucose) • Starch molecules can have two structures: • Amylose = molecules are linear; they're long and narrow like a line • Amylopectin = have multiple branches, like the veins in a leaf

11. Structure of Fiber/Carbohydrates in the Body • The main plant fiber found in food is cellulose, a polymer made of a form of glucose called betaD-glucose • Other basic structures of edible fiber include hemicellulose, pectins, and algal polysaccharides

12. Carbohydrates in the Body • 55-65% of your daily calories should come from carbohydrates, mostly complex (300g) • Glucose is the main carbohydrate found in blood

13. Hydrolysis of Sugars • Hydrolysis = splitting of a compound into smaller parts by the addition of water • This reaction breaks down carbohydrates until they yield the sugars from which they are formed • Hydrolysis of sugars results from the action of enzymes, certain proteins that control chemical activities

14. Blood Glucose Levels • The pancreas monitors the flow of glucose to the cells. • During digestion, the pancreas secretes the hormone insulin • Hormone = a chemical messenger that affects a specific organ or tissue and brings forth a specific response • Insulin also helps keep glucose in the blood at a normal level • If blood glucose is too high, insulin triggers the liver and muscle cells to remove glucose from the blood and store it as glycogen.

16. Questions • How is the term “carbohydrate” related to the nutrient’s composition? • How are carbohydrates involved in transferring solar energy to people? • Compare monosaccharides and disaccharides, using examples to illustrate. • In developing a new recipe, why might you use fructose instead of sucrose? • How would a chemist describe a complex carbohydrate? • What would happen if carbohydrates in your body were not hydrolyzed.

17. Questions Continued • Describe the process that ensures your body a steady flow of glucose. • Compare the complications of Type 1 and Type 2 diabetes. • What is nutritionally significant about fiber? • Suppose you forgot to calibrate your thermometer before making candy. It registers 10°C less than the actual temperature of the syrup. What may result? • How do amylose and amylopectin affect thickening? • Why do food scientists modify starches for food production?