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Plan an investigation to find out what increases the rate of fermentation.

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Introduction

Further Science Coursework Name: Daniel Wingrove 10Y Date: 4-12-2001 Problem set: Plan an investigation to find out what increases the rate of fermentation. Scientific knowledge: Yeast Yeast is a microorganism which grow by feeding on sugars. In food manufacture, yeast is used in fermentation and leavening. The fungi feed on sugars, producing alcohol (ethanol) and carbon dioxide. The carbon dioxide is used in beer and wine manufacture. In sparkling wines and beer some of the carbon dioxide is retained in the finished beverage. The fermentation of wine is initiated by naturally occurring yeasts present in the grapes. One yeast cell can ferment approximately its own weight of glucose per hour. Yeast is also used in making bread. The yeast respires with oxygen by feeding on sugars, breaking them down into carbon dioxide, water and alcohol (Ethanol). The carbon dioxide makes the dough rise, the bread is then baked in an oven for 30 minutes. This kills the yeast and evaporates the alcohol. This is how bread is made. Fermentation For thousands of years, the process of fermentation has been used to make bread, beer and wine. Today fermentation is used to make foods such as bread and yogurt, alcoholic drinks such as wine, drugs such as penicillin and chemicals such as methanol and citric acid. ...read more.

Middle

Temperature control during alcoholic fermentation is necessary to (1) facilitate yeast growth, (2) extract flavours and colours from the grape skins, (3) permit accumulation of desirable by-products, and (4) prevent undue rise in temperature, denaturing the yeast cells. Wine making and bread making are two examples of biotechnology, this means using microbes, plant cells or animal cells to make substances that are useful to us. Many useful chemicals have been produced using fermentation techniques. There are many experiments to test that Yeast + water + glucose ? CO2 + Ethanol. One of these is to use two test tubes one filled with yeast suspension plus diazine green and liquid paraffin on top. This is to prevent oxygen reaching the yeast. The other is filled with hydrogen carbonate indicator solution and the test tubes are connected with a delivery tube. This test is to see whether yeast can respire anaerobically (Without air). If the hydrogen carbonate indicator solution turns yellow it means that no oxygen was present when the yeast respires. However, if the hydrogen carbonate indicator stays pinkish colour oxygen was present when the yeast fermented. Another previous test has proved that oxygen is not necessary for respiration. ...read more.

Conclusion

If the yeast in the heated boiling tube produces 1ml of CO2 faster than the yeast at room temperature then this will show that temperature does have an effect on the speed at which yeast ferments. This is a prediction of the results I expect from my experiment. Predicted Results A Graph Predicting the Effect of Temperature on the Speed of Carbon Dioxide Production Apparatus list: 2 x Bunsen burners or water baths 2 x boiling tubes with two holes in the bung (the first to hold a thermometer and the second to hold a syringe that shows how much carbon dioxide is produced). Yeast Water Sugar 2 x tripods Beakers Gauzes 2 x stop clocks Method Measure out the amounts of yeast, water and sugar that will be needed in the experiment. Then fill two beakers half full of water and heat one of them to 380c and leave the other at room temperature. Put the two boiling tubes in the beakers of water. Then add the yeast, water and sugar into the boiling tubes and start the timer. Record how long it takes for 1ml of carbon dioxide to be produced in each boiling tube. Fair test: I will repeat this test five times to make sure I get reliable results. I will only change one variable and that will be the temperature. By Daniel Wingrove 1 ...read more.

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