Optimum temperature for bakers
A bread maker wants you to investigate the optimum temperature for his bread to rise. The bread rises because yeast is added to the dough. Yeast is a living organism that respires using glucose and oxygen and produces carbon dioxide like we do.
Glucose + Oxygen Carbon Dioxide + Water
Yeast also can ferment if there is little oxygen and this also produces carbon dioxide and ethanol. The carbon Dioxide bubbles are trapped in the dough making the dough rise.
The baker wants to know what temperature causes the yeast to respire the quickest therefore causing the dough to rise faster.
In this practical you are going to look at how temperature effects the respiration of yeast. By recording the volume of carbon dioxide produced by the yeast and sugar solution at different temperatures you can tell which the optimum temperature for respiration is.
Procedure:
1. Set up the apparatus as shown below.
2. Using a syringe take up 3cm3 of the yeast solution and place in a boiling tube.
3. Add 5 cm3 of the glucose solution to the yeast.
4 Place the boiling tube in the polystyrene cup full of 20oc water
5. Leave for two minutes to allow the yeast to acclimatize
6. Record the amount of CO2 produced after 2 mins using the measuring
cylinder
7. Now change the temperature of the water in the cup to 30oc.
8. Repeat the steps above placing the yeast in the appropriate water baths
up to 60oc each for 2 mins.
Risk Assessment
You must now complete a risk assessment for the practical.
Use the hazcards and cleapps guide to look for use of glassware and hot water in the water baths.
Obtaining Results.
Draw a table of your results here.
Don’t forget to use the correct headings and units.
Analysing your experiment
Draw your results as a graph.
You need to choose the correct type of graph for your data.
Think about the scale for each axis and units etc.
1. What pattern does the graph show you?
2. Why is there this pattern?
3. What is the best temperature for the baker to leave his bread to rise?
4. Explain what will happen if the temperature is too low or too high and why
it will happen.
- What evidence is there to suggest this is the best temperature?
Evaluating your experiment.
1. Did you repeat your experiment and get the same results?
2. Did all your results fit the same pattern?
3. Was your experiment precise? Which apparatus did you use to measure the carbon dioxide produced?
4. Could you improve your experiment to get more precise results?
5. Do you think that you would get the same conclusion if you did this experiment again? Why?