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Topic: bacteria lab with pH sensor (Read 6934 times)
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PetersonJ
Newbie
Posts: 4
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I am always looking for new ways to use Vernier technology in my 7th grade science class. We are currently learning about viruses and bacteria. I have seen many activities where students make their own yogurt but many of these labs lack a data component. I decided to try out my Vernier pH sensor to observe how the pH changes over time.
I used Damon plain yogurt which contains active L. Acidophilus cultures. I added about 2 Tbs to about 200 mL of 2% milk. The beginning pH was 6.00 at a beginning temp of 14.5C. I put the mixture of bacteria and milk into a warm water bath at 35C. In just 24 hours, the pH was down to 3.66. I continued to test for several days to see if I could get the bacteria population to crash. After three days, I am going to stop the test.
Here is the resulting graph of pH.
I might test it again later to see if I can get it to crash to use it as an example of a good bacteria growth curve.
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tristero
Newbie
Posts: 2
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Did you do a control where you measured pH over the same time period in a sample that was not inoculated with yoghurt?
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PetersonJ
Newbie
Posts: 4
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I have not done that but it is a good idea! I am about to try it again this year and will include that data.
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