FS Homework Sheet_ Carbohydrates Polysaccharides (1)

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Food Science—Carbohydrate Homework: Polysaccharides Please review the Learning Module on Carbohydrates for further understanding of carbohydrate chemistry. You’ll need to read the Dextrinization and Roux articles to answer questions on dextrinization. Vocabulary 1. Oligosaccharide: A carbohydrate molecule made up of three to ten sugar molecules. Cannot be digested by the body. An intermediate size saccharide linked together with chemical bonds. 2. Polysaccharide: A carbohydrate molecule made up of tens to hundreds to several thousand monosaccharide units linked together in chains. Starch, cellulose and other fibers, and hydrocolloids are all polysaccharides. Higher saccharides with many sugar units; usually between 10 and 2 million sugar units all linked together through chemical bonding. 3. Maillard Browning: A non-enzymatic browning reaction that occurs when reducing sugars interact with amino groups on proteins, ideally with dry heat. A series of complex reactions occur resulting in color and flavor molecules. The sugars must be reducing sugars, or sugars with a carbonyl functional group. Involves the breakdown of sugars, the carbonyl group on a sugar, and the amino group on an amino acid, which are the building blocks of proteins, reacting and creating brown colors and flavors. This reaction takes place at high temperatures, greater than 300F when carbohydrates/sugars and amino acids/proteins are present. 4. Dextrinization: The non-enzymatic process that involves the browning of starch foods when subjected to dry heat. It is the breakdown of starch into dextrins. Starch molecules break into fragments and rearrange themselves to create new flavor and color compounds. Example: roux being cooked to increasingly dark stages. Temperature must reach over 300F, the brown colors and flavors are created only under these conditions. Water must not be present, or the process will not occur properly as the proper temperature cannot be reached. Involves the breakdown of starches at high temperatures greater than 300F. 5. Non-enzymatic browning: A browning reaction that does not involve the use of an enzyme. It is a set of chemical reactions that are responsible for the formation of complex flavor compounds and brown pigment compounds. Examples include Maillard browning and caramelization. 6. Enzymatic browning: An oxidation reaction that requires an enzyme and oxygen and causes various foods to turn brown. This reaction mostly occurs with fruits and vegetables. Examples include the browning of avocado and the browning of an apple when sliced open.

7. Hydrolysis: The use of water, “hydro,” to break, “lyse,” covalent bonds; breaking down organic molecules into their smaller counterparts. The more acid and the longer the heat, the more hydrolysis. The breakdown of higher polymers into monomeric units with the addition of water. 8. Oligomerization: A chemical process in which a monomer or a mixture of monomers is being converted into an oligomer. Part 2: Short Answer 1. Explain the difference between soluble and insoluble dietary fiber. Soluble fiber dissolves in water, it is hygroscopic and slows digestion. It includes plant pectin and gums. Insoluble fiber does not dissolve in water and helps with regularity. It includes cellulose and hemicellulose. Soluble fiber can be hydrated by water; insoluble fiber is packed too tightly for water to get in and hydrate the molecules which makeup the fibrous bundles. Neither kind of fiber can be digested by humans; we do not possess the digestive enzymes necessary to break down fibers into their monomer units. None can be absorbed through the gut and into the blood stream larger than a monomer, with respect to carbohydrates and proteins. 2. Describe Starch Gelatinization: Gelatinization is a physical and chemical process that combines starches and water in the presence of heat. This causes the starch to swell and absorb the water trapping network. The two factors that must be present for starch to gelatinize are 1. Water and 2. Heat. Separating each starch granule into a roux or slurry is crucial to prevent lumps, promote even thickening, enhance solubility, and prevent burning. Dry starch cannot be added to boiling water because there is a risk of lumps, incomplete gelatinization, and inconsistent thickening. When starch granules are in the presence of water and heat, they will begin to absorb water. This causes the starch granules to swell and thicken. As this process is continued and more heat is applied, some granules will burst and release starch molecules into the surrounding medium. Maximum thickening is achieved when the granules are at their maximum swelling, and some molecules have separated from the granule. The separated molecules go on to form a network which traps water and the swollen granules. Thinning can occur if the heating continues, and the granules lose their structure entirely, or “burst.” The thickening power of the sauce is lost from the swollen granules, but will keep thickening because of the starch fractions that have spilled out. a. When answering the question, be sure to include the two factors that must be present in order for starch to gelatinize and… Heat and water. b. Describe why it is important to separate each starch granule from each other before applying heat (why do you need to make a slurry or a roux before heating the starch)? And…

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