The Affects of Different Yeast on the Rate of Fermentation

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AIM: To see how different yeast affect and influence the rate of fermentation, how much alcohol is being produced and how this affects the overall quality of wine produced. BACKGROUND INFORMATION: Alcohol, is mostly thought of as ethanol which is the alcohol which is found in alcoholic beverages such as wine and beer. But there are many different varieties of alcohol such as methanol, propanol and butanol. In chemistry terms “alcohol” is a compound of a hydroxyl group which is covalently bonded to a carbon chain which can be seen in figure 1. Throughout this experiment ethanol is the alcohol which is produced during the fermentation process of sugar which is present in the grape must or juice. Figure 1: Chemical structure of Ethanol (Wikimedia, 19 July 2009) Yeast is a single celled living organism which is necessary in the process of fermentation of the grape must. Invertase, an enzyme is present in yeast acts as a catalyst to speed up the chemical reaction where sucrose is converted into fructose and glucose. (Donal O’Leary, 2000) Figure 2: The word and balanced equation of the conversion of Sucrose to simple sugars (Donal O’Leary, 2000) Another enzyme which is found in yeast is known as Zymase. It is this enzyme present in yeast which converts the glucose and fructose produced into ethanol and carbon dioxide. (Donal O’Leary, 2000) Figure 3: The word and chemical equation for the conversion of simple sugar to ethanol (Donal O’Leary, 2000) In the making of wine there are 2 fermentation processes known as • Primary Fermentation • Secondary Fermentation In the process of primary fermentation the sucrose in converted into glucose and fructose and the gluc... ... middle of paper ... ...s for their growth and development. 5mL from each bucket was added to the specified beaker and left for 10 minutes. 90mL was then added to there specified beaker and left for another 10 minutes. This process activated the yeast. Once the yeast was activated they were added back to their specific bucket into 1 point in the grape must. The grape must was not stirred and was slowly and carefully placed into a cooler environment where the fermentation process could begin. After 8 days in primary fermentation the grape must was filtered using a sieve and a chuck cloth to remove any dead yeast and grape skins. The grape juice was then poured into the specified bottle and an air lock was placed on top to prevent oxygen from entering but allowing carbon dioxide to escape so that pressure did not build up in the bottles. This started the secondary fermentation process.

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