BackgroundAs you can see, bread,cakes, and cookies all lookvery different even thoughthey are made from almostthe exact same ingredients.The cause of thesedifferences is the leaveningprocess.Cakes and cookies arechemically leavened, butbread is leavened by yeast.
Bread LeaveningWhen people bake bread, they are also makinga chemical reaction.This chemical reaction, usually involving yeast,is called alcoholic fermentation.The yeast ingests the sugar in the bread doughwhich breaks down into ethyl alcohol and carbondioxide.The ethyl alcohol and carbon dioxide are themost important part of the chemical reaction.
Bread LeaveningThe carbon dioxidecreates air bubbleswhich make the “light,airy texture of bread.”The carbon dioxidedoes not escape thebread because a glutenprotein in the wheat ofthe flour forms anetwork of fibers thatblocks the air bubblesfrom escaping.
Bread LeaveningThe wheat used inbread dough containsenzymes that act ascatalysts to thereaction.Ethyl alcohol is equallyimportant as itcontributes to the tasteand smell of the bread.Organic acids, esters,and ketones are alsoproducts made during
Cake and Cookie LeaveningThe wheat used to make cakesand cookies does not contain asmuch gluten as the wheat usedto make bread.Because of the lack of gluten, thecarbon dioxide is not easilytrapped inside cakes or cookies,so an acid-base reaction is used.In many recipes, baking soda(sodium bicarbonate) acts as thebase in the reaction, and the acidcan be a variety of ingredients.The most common acid used isbaking powder, which is actuallya combination of acids thatrelease carbon dioxide at
Cake and Cookie LeaveningCalcium biphosphate is theacid used in most bakingpowders, but sodiumaluminum sulfate may alsobe used.When the acid is dissolvedin water, hydrogen ions arereleased and “react withthe bicarbonate ions fromthe baking soda”.This important acid-basereaction occurs so that thecake and cookies are light
Works CitedAshe, Arthur J. , III. "Yeast." World Book Advanced. World Book, 2013. Web. 7 Apr. 2013.<http://www.worldbookonline.com.candycorn.lipscomb.edu/advanced/article?id=ar613160&st=yeast>Connick, Wendy. "The science of bread." Countryside & Small Stock Journal Mar.-Apr. 2011: 70+. General OneFile. Web.7 Apr. 2013. <http://go.galegroup.com.candycorn.lipscomb.edu/ps/retrieve.do?sgHitCountType=None&sort=DA-SORT&inPS=true&prodId=GPS&userGroupName=tel_a_beaman&tabID=T003&searchId=R1&resultListType=RESULT_LIST&contentSegment=&searchType=BasicSearchForm¤tPosition=1&contentSet=GALE%7CA249956737&&docId=GALE|A249956737&docType=GALE&role=ITOF>"Fermentation of Sugar in Bread by Yeast." Kinetics of Cooking. Arizona Board of Regents for The U of Arizona, n.d. Web.7 Apr. 2013. <http://blowers.chee.arizona.edu/cooking/kinetics/kinetics.html>.http://blowers.chee.arizona.edu/cooking/kinetics/bread.html"On the Rise." Chemistry World Oct. 2009: 54-57. RCS. Web. 7 Apr. 2013.<http://www.rsc.org/images/BreadChemistry_tcm18-163980.pdf>.Rudolph, Melissa. "Leavening: How Great Cooks Loaf." Chem Matters Apr. 1996: 4-6. Print.