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Fermentation of Yeast

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Stephanie Clayton- Fermentation of Yeast What is Yeast? *A single-cell fungi that form masses of minute circular or oval cells by budding. *When placed in a sugar solution the cells multiply and convert the sugar into ethanol and carbon dioxide. * Yeast are used as fermenting agents in baking, brewing, and making of wine and spirits. *There are lots of different varieties of yeast that can be used for industrial purposes and simply in the home. *Yeast grows wherever there is suitable food, most commonly found wherever sugar occurs. *The scientific name for yeast is 'saccharomyces' it means 'sugar-fungi'. *For many years yeast has been used to ferment the sugars in rice and barley to produce beer, and the sugar in grapes to make wine. *Yeast is also added to dough, which ferments the sugar in the dough to produce carbon dioxide, which causes the dough to rise and form bread. *When yeast is given food the cells grow and multiply, the diagram below shows a single-cell from a yeast plant: *Yeast does not need oxygen to survive. *The equation for fermentation is: Glucose = ethanol + carbon dioxide *If yeast is exposed to yeast it makes less ethanol and grows at a much slower rate. *If there is a good supply of food, a suitable temperature, and water, budding occurs at a faster rate. ...read more.


As in some cases the gas collected can be different therefore collecting the gas at one particular temperature means you will end up will a more accurate sample of gas. The measurements are taken after 2 minutes after the temperature has been reached: 1 2 3 30 1ml no more gas produced no more gas produced 40 6.8ml 4.2ml 8ml 50 10ml + 6ml 2ml 60 8ml 1ml 2ml Graphs to show the results are on the next few pages Results Conclusion My aim at the beginning of this investigation was to find out the effects of temperature in the process of fermentation. My prediction was that when I reached the temperature of 40 the amount of carbon dioxide produced would be at its greatest. From the final set of results I gathered I found that this confirmed my earlier predictions. In my prediction I also stated that after 40 the enzymes in the yeast would be 'denatured' because the enzymes had passed their optimum temperature, therefore less gas would be produced. This is also shown clearly in my result table. During my investigation each temperature I measured the amount of gas at, I took three results. My purpose was to establish an accurate measurement of carbon dioxide. ...read more.


There are 4 main stages in the yeast growth cycle: Lag phase Rapid growth Growth slowing Population constant In the investigation my aim was to get the yeast into the two middle stages of rapid growth and growth slowing. As the fermentation process reaches a certain point it stops. This is because the enzyme produces carbon dioxide and alcohol, the alcohol acts as a poison on the yeast population and kills the yeast. If I were to do any extension work concerning this investigation I would look into the optimum temperature of the enzymes. I would find a method to try and test the temperature around 40 to see how much carbon dioxide is produced just before and after to see how the enzymes deteriorate after they have reached their optimum temperature. You could also look at the gases that were produced along with the carbon dioxide collected in the first two sets of results. I would have to research how I could test to see what the gases were, I would then be able to distinguish what was carbon dioxide and what wasn't at the particular temperature. Also if I were to investigate further I could use different types of sugar or yeast. These are all different paths I could look into. There are many other ways you could take this investigation but from this aspect of how temperature affects fermentation has been very successful. From taking it further I could only learn more about fermentation. ...read more.

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