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Annual science fair projects were mandatory when I was in school, so they inevitably turned out to be some hastily thrown together mess with a pretty display board. However, there is one project that stands out from the rest because it was the one project that I produced because I was genuinely interested in the results. As a child, I would often forget to put the milk back into the refrigerator and would get yelled at for potentially causing it to spoil. After I completed my experiment and compiled the results, I actually had a defense that even my parents couldn't argue with when I accidentally left the carton out overnight.

Purpose

The purpose of the investigation was to ascertain the bacterial content of refrigerated whole, refrigerated skim, and standing whole milk after twenty-four hours and forty-eight hours.

Hypothesis

It was hypothesized that the milk that had already been standing at room temperature for several hours would contain the most bacteria, followed by the refrigerated whole and then the refrigerated skim. The control sample, refrigerated whole that had never been left standing, would remain the same due to never being exposed to experimental conditions and would contain the least bacteria.

Materials

20-ml. refrigerated whole milk (kept in refrigerator as the control)
20-ml. refrigerated whole milk
20-ml. refrigerated skim milk
20-ml. room temperature whole milk
4 droppers
4 test tubes and test tube stoppers
1 bottle of methyline blue indicator with dropper
Large beaker half-filled with water
1 Bunsen burner

Experiment

Keep sample temperature a constant 98 degrees (preferably 98.6) on a Bunsen burner in order to stimulate conditions inside the body. Use methyline blue to indicate bacterial content of samples. Record bacterial content after twenty-four hours, and again after forty-eight hours.

Procedure

20-ml. of refrigerated whole milk, 20-ml. of refrigerated skim milk, and 20-ml. of whole milk that had already reached room temperature were placed in test tubes.

20-ml. of refrigerated whole milk were sealed in a test tube and placed back in the refrigerator as the control sample.

2 drops of methyline blue were added to each tube.

All test tubes were sealed and placed in a beaker of water atop a Bunsen burner, where they were left for twenty-four hours.

Bacterial content was measured after twenty-four hours, then again at forty-eight hours, against the control sample and against other experimental samples.

Results

The control sample contained the least amount of

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