Problem: Will bacteria grow less quickly in Parmalat than in regular milk.

Hypothesis: The bacteria will not grow as fast in the Parmalat as in the regular milk.

Procedure: I first took a petri dish out of the refrigerator and drew a line on the bottom of it. Then I wrote a “P” on one side of it for Parmalat, an “R” on the other for regular milk, and the date. Using a sterile loop, which is a rod with a circle on the end used to take samples, I dipped it in the regular milk and smeared it the short way on the “R” side for a concentrated sample and the long way for easy counting later. I repeated this process for the Parmalat. After one day in room temperature, I sealed it and returned it to the refrigerator so it wouldn’t grow anymore. Every other day I repeated this process. When I am all done I will view each sample under the microscope and count the total amount of bacteria in each. Then I will make a chart of the increase of bacteria in each.


My project is to determine whether the bacteria in Parmalat grows more slowly than regular milk.
I think the Parmalat will grow less bacteria than the regular milk.
I took a sample of both types of milk and spread them on a petri dish containing agar. After 24 hours I put the culture into the refrigerator to stop growth. When the regular milk was too stiff to take samples, I stopped. When I was done, I counted the number of colonies.
The Parmalat didn’t grow as fast as the regular milk because it had been ultra pasteurized and there was less bacteria in it to breed other bacteria.

Results: The regular milk started to grow from the start. After a while the waste from the bacteria started to kill off itself and stop growing. The Parmalat never grew, even at the end of the experiment.

Conclusions: If milk companies all pastuerized their milk the way parmalat did then they would lose a lot of money, because people that do not use much milk would only buy a carton of milk when they needed it instead of when it went bad.

Growth of Bacteria
Day Regular Parmalat
Day 0YesNo
Day 2YesNo
Day 4YesNo
Day 6YesNo
Day 8YesNo
Day 10YesNo
Day 12YesNo
Day 14YesNo