Making Cheese. Cheese-Making Lab is great for: Showing how biotech has impacted an industry. Introducing scientific methodology (experimental design, data collection (data tables/graphs/data analysis, conclusions). Demonstrating the effects of too many variables.
Cheese-Making Lab is great for:
Which curdling agent produces cheese the fastest?
Which curdling agent produces the most cheese?
To examine numerical data for support of predictions.
To examine variables that can lead to invalid experiments.
Hypothesis: ______ is expected to produce the most volume of cheese in the shortest amount of time because it _________________________.
1. Using a 10 mL pipet and pipet pump, transfer exactly 7 mL of whole milk into a labeled, 15 mL conical tube.
2. Using a pre-set micropipet, add 0.25 mL (250 uL) of one of the four curdling agents to the 7 mL of milk.
Use either: buttermilk, rennin, chymosin, or dH20 (- control) as assigned by your supervisor.
3. Cap the tube and gently mix by inverting 3 times. Record this “initial time”. __________
4. Place the milk-containing portion of the tube deep in your armpit, like a thermometer, and incubate it there for at least 15 min.
5. Check for curdling every 5 minutes, recording the time to curdling in minutes. To check for curdling, gently tilt the tube, careful to not breakup any curds. Curds are large lumps of solidified milk. After 15 min, place the tube upright, at room temperature and check for curdling every 15 min for 2 hours. If curdling has not occurred within 2 hours, continue checking once every four hours. With the greatest accuracy possible, record the number of minutes passed until the milk had curdled to the greatest extent.
6. If curdling has not occurred by the end of the class period, bring the tube home (keep at room temperature) and back to class in 24 hours. Keep tube upright so any curds fall to the bottom of the tube.
7. On return to the lab, measure the amount of curds (solids) and whey (liquid) in the tube. You may be able to read the volume of each directly off the tube although it may be difficult. Better yet, filter it as described below, using a “whey-o-meter”.
8. If necessary, pour the whey and curds mixture through a filter paper funnel into a 10 mL graduated cylinder (a “whey-o-meter”). Determine the volume of whey collected in the graduated cylinder, using a pipet if necessary to measure small amounts. By subtraction, determine the volume of curds. Can you suggest other methods of determining the amount of curds produced in each treatment?
9. Record the data for your sample plus one each of the other variable groups on the data table below. Record the name of the person from whom you have gotten data.
Fill in the Blank-o-Meter
Using Excel®, the lab supervisor will collect each individual’s data to make a class data table showing multiple replications of the experiment. Averages for each variable group should also be recorded on this data table. Averaged data is the best answer to an experimental question. Can you explain why?
11. Using Excel®, produce two graphs; one which shows the average time to curdling for each enzyme treatment and one which shows the average volume of curds produced by each enzyme treatment. Use the Excel® tutorial if necessary.
Imagine you are an employee at a cheese curdling company and you must summarize the results of your experiments and give your supervisor the best answer to the scientific questions asked. Write a conclusion that reports the Results of the experiment (answer to the purpose question) including Evidence and Explanations for your findings. Discuss how well the results support the hypothesis. Identify sources of Possible Errors in the technique that may lead to variations in results (see next slide). Think about the Practical Applications of the results of the experiment. Make a recommendation to the cheese company supervisor about which curdling agent should continue to be the focus of production. Include any variations in the procedures that you think may improve the cheese production.
13. In the biotechnology industry, the work of others is reviewed and “OK’d” by peers. This is called “witnessing”. When you witness data and analysis, check for:
Textbook with Encore CD ISBN: 0-7638-2282-5 … Chapter 1 Bioethics
Laboratory Manual ISBN: 0-7638-2285-X … Lab 1c
Textbook with Encore CD and Lab Manual ISBN: 0-7638-2278-7
Text with Encore CD and Lab Manual and Lab Notebook: 0-7638-2279-5
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For Biotech Materials Lists:
… Master List Lab 1c