Fermentation Experiment

Fermentation with yeast can be used to produce alcohol to make beer, wines and spirits.

Fermentation with yeast can be used to produce carbon dioxide used in bread making.

                       

   

                                                                   

Experiment 1

Finding out about fermentation

I will need to set up two experiments as shown in the diagram below. One experiment will show me how yeast respires anaerobic ally to produce carbon dioxide. The other will act as a control.

Method:

1. Boil some distilled water in a 100cm beaker to remove the air from it.
2. Place 10cm of boiled water into a clean beaker and add two teaspoons of sugar. Stir to dissolve the sugar and allow to cool.
3. Place the solution into a clean test tube and add one teaspoon of yeast.
4. In a separate test tube, add 10cm of warm boiled water and one teaspoon of yeast.
5. Add a thin layer of liquid paraffin to each tube by carefully running it down the side of the test tube using a dropper (as shown in the diagram above).
6. Place 10cm of limewater into each of two clean test tubes. Connect up the two experiments as shown in the diagram.
7. Record results

     After doing, the experiment I found out that the experiment with the sugar solution in made the limewater cloudy/chalky this shows that it gave off carbon dioxide, unlike the one without the sugar didn’t do anything.

Questions

Why must the water be boiled?

     The water must be boiled to make it sterile, this gets rid of the air and kills any germs that are hanging around near by.

Why is the sugar solution cooled before adding the yeast?

    The reason for this is that, that’ the temperature the yeast works best at, if the temperature is too hot it will kill the yeast but if it’s too cold then the yeast won’t work.

What does the liquid paraffin do?

    Liquid paraffin is oil so it keeps oxygen out.

 

Conclusion

 

    After doing the experiment, I think that you do need sugar for yeast to work, sugar is what the yeast feeds on so you need enough sugar to make the yeast raise the bread.

    In my background research, it says that in order for the yeast to work, you need carbon dioxide to be produced, by doing the experiment; I found that when I used the sugar solution with the yeast it gave off carbon dioxide this proves that you need sugar in your recipe for the yeast to work.

Evaluation

     Looking at the table of class results I noticed that some people’s bread rose without any sugar added in their recipe, There were some errors during the experiment one of the errors was that some of the pupils added more flour than the amount that they really needed, the more flour you have the harder it is for your bread to rise, by amending this error they can repeat the experiment and be more careful in measuring their flour. Another error that we had was that we didn’t measure the temperature where we put our yeast mixture to rise, so if we were to do this experiment again then we should measure the temperature with a thermometer before letting our yeast mixture warm for 2 hours. Not measuring the yeast accurately was also a problem, as we didn’t use a teaspoon instead, we used a spatula.

Experiment 2

             

      Investigating the conditions required for fermentation

     

        In this investigation, I will be making bread dough, using different amounts of sugar. Yeast needs sugar as a source of food to produce energy, and the waste product carbon dioxide is used in bread making to make the bread rise. I can vary the amounts of sugar used to make dough and measure how much the dough rises.

      This experiment will be done as a class practical. My tutor will allocate which of the experiments A-E I will do and the results will be combined at the end of the experiment.

Method:

1. Warm some water in a beaker. The temperature should not be above 40c
2. Fill a test tube to half way with warm water and add the yeast and sugar (if any). Stir gently to mix.
3. Add the yeast solution to the flour and add enough warm water to form dough. Be careful not to put too much water in!
4. Place the dough into a measuring cylinder and record the “volume” of dough using the scale on the side of the measuring cylinder.
5. Place the dough in a warm place for one hour.
6. Measure the new”volume”of the risen dough.
7. Record the rest of the results

Results:

Experiment 3

Making bread

I will need:

50g flour

Sugar-the amount I have decided to try following my previous investigation

1 teaspoon of yeast

Warm water-no hotter than 40-45

1. Put the yeast into a test tube and add about 10cm of warm water. Shake gently to mix.
2. Add sugar and shake gently again.
3. Add the yeast and sugar solution to the flour and add enough warm water to make dough.    Do not add too much water!
4. Place on a baking sheet and leave for about two hours for the dough to rise.
5. Bake in an oven at 200C for 10 to 15 minutes.

Evaluation

      I used 1g of sugar in my recipe, and my bread rose nicely, I don’t think there were any problems when baking this bread, as I put the right amount of water in my recipe making sure it wasn’t sticky to make into shape, If I were to do this experiment again then maybe I will try and measure the flour more accurately and use a thermometer to find out the water temperature.