The Effect of Cooking Temperature on the Amount of Bacteria in Ground Beef (8/13/2009) The results are exactly what you can expect to happen in class

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The Effect of Cooking Temperature on the Amount of Bacteria in Ground Beef (8/13/2009) The results are exactly what you can expect to happen in class. I encourage you to have some great discussion with you students about the results. I love drawing conclusions from results; it is the thinking part of the investigation. Please dont be offended by my notes. As scientists, we need to be critical of the experimental procedure and the results obtained. We are the checks and balances of the scientific method. Without our ability to think and reason, the experiment/data mean very little. Remember, the interpretation of results may lead to modification of the experiment, not necessarily answers!! Slide 2 Slide 3 What happened here? Teachable moment! I love it when this happens!!!!!! Slide 4 Notice the lack of uniformity in the plating process. This results in differing number of colonies due to procedure, not bacteria present. Slide 5 Nice results!!!!! However, notice the writing covers some results. Again, the plating/swabbing is not uniform on all plates. Slide 6 These guys had a great time! Observations were recorded directly on the platesprobably would be better to record in lab journal. Slide 7 Explain the lack of difference between 120 and 140 o Fwe need more trials dont we. Slide 8 Quantifying Data: Counting Colonies From the back/bottom of the sealed plate, count each colony (spec) of bacteria As you count mark the colony with permanent marker I count the first 100 colonies, then I let my partner count the next 100. We trade off until all colonies are counted. Slide 9 The black dots are the colonies I counted. Using the marker is essential to keep track of counted colonies. Note: It is important to remind students that not all of these bacteria here are pathogenic. If you purchase meat at your local supermarket, the facility where the meat was processed and the supermarket are inspected for pathogens and/or bad practices. Sometimes the meat even goes through an irradiation process to kill the bacteria. However, we all know that finding E coli 0:157 is like finding a needle in a haystack. It could be in your burger. Slide 10 1 bacterium after 24 hours of incubation at 37 o C = 1 colony of bacteria Results: 0 colonies (interpretation: no bacteria on TSA plate) Slide 11 Results: 500 colonies (interpretation: WOW, theres a lot of bacteria in ground beef. I hope none of them are pathogenic!) note: youre right, I didnt really count them ;-) Slide 12 Results: 400 colonies (interpretation: 120 o F is not very effective at killing bacteria) (Practical application: If any of these bacteria are pathogenic, I am at risk of ingesting a food-born pathogen when I eat this rare burger.) Slide 13 Results: 70 colonies (interpretation: 140 o F is relatively more effective at killing bacteria when compared to 120 o F.) (Practical application: Nick Adams, colleague here at West, says he would eat this burger. There is still the potential for food-born illness if the bacteria are pathogenicSalmonella or E coli 0:157. Slide 14 160 o F Results: 0 colonies (interpretation: ????) (Practical application: ????) Slide 15 Have a great year of discovery, intrigue and enlightenment through scientific investigation.