Bacteria in Raw vs. Cooked Meat

Research Questions:

How can you spot bacteria under a microscope? Is it difficult to do?

We cook meat to eliminate harmful bacteria. Eating raw meat can be very risky as it contains contaminants such as salmonella, which causes severe upset stomach, diarrhea, vomiting, and fever. Students will learn to identify bacteria under a microscope by shape and structure. If they want to go further to identify the type of bacteria, then additional tests are required with stains.

Materials:

• Cooking range
• Skillet/ saute pan
• Raw meat samples (raw pork, meat, chicken, etc)
• Water
• Microscope
• Well slide
• Rubber gloves
• Pen and paper for notes

Experimental Procedure:

1. Prepare the well slide: place a small chunk of raw meat inside the slide.
2. Observe the raw meat under a microscope. Look for bacteria. Bacteria is recognizeable because of its stringy shape and one-celled structure without a true nucleus. Read this guide for details.
3. Approximate how many bacteria are in the sample. Are they a lot?
4. Take one of your raw meat samples and place it in a prepared, heated skillet to cook it for about 10-14 minutes on each side. Add water if necessary, do not burn the meat.
5. Remove from heat and let it cool down for 10 minutes. Take a small chunk of meat and put inside the well slide.
6. Observe the cooked meat under a microscope. Search for any bacteria. If bacteria is present, approximate on the number.

Terms/Concepts: Bacterial formation; Cooking; Destruction of heat; Dangers of bacteria

References:

• http://www.disknet.com/indiana_biolab/b038.htm
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