Bacteria and thawing methods
The materials required for this science fair project are:
- 3 agar Petri dishes
- 3 disinfected swabs
- 1 bottle of disinfected water
- 1 sterilized chopping board
- 1 sterilized knifes
- 1 refrigerator with freezer
- 1 microwave oven
- 1 piece of irradiated chicken part bought from the cold storage supermarket
- 3 beakers
- 1 Marker pen
1. The independent variable for this science fair project is the method of defrosting the chicken meat – at room temperature, in a refrigerator and using the microwave. The dependent variable is the size of the bacteria growth in the Petri dish. This is determined by measuring the size of the bacteria growth using a ruler. The constants (control variables) are room temperature, the amount of sunlight and the ingredients in the Petri dish agar.
2. Prepare 3 Petri dishes are prepared using agar and store themin a refrigerator. The Petri dishes are brought to room temperature before the start of experiment by taking them out of the refrigeratorLabel the Petri dishes as “Room temperature”, “Fridge” and “Microwave”.
3. Using a knife and a chopping board, cut out 3 equal cubes of irradiated chicken meat Keep the chicken cubes inside the freezer for a day.
4. The next day, the 3 pieces of frozen chicken cubes are removed from the freezer. Remove the 3 cubes of frozen chicken from the freezer the next day. Keep the 1st cube of chicken in the fridge for the next 12 hours to thaw . Leave The 2nd piece of chicken at the kitchen counter for the next 4 hours to thaw at room temperature. Use the microwave to thaw the 3rd piece of chicken
5. Label the 3 beakers as “Room Temperature ”, “Fridge” and “Microwave”. Pour 100 ml of disinfected water into each beaker and soak the thawed meat in it, according to the labels on the beaker for ten minutes.
Wash the swab with sterilized water and dip it into the beaker. Swipe the swab at the center of the agar surface according to the label on the beaker and Petri dish
6. . Cover the Petri dishes and keep them in a cool, shaded place for the bacteria to grow, for the next 5 days.
7. Measure the diameter of the bacteria colony growth after 5 days and recordit in the table provided below.
Always follow laboratory safety guidelines and always practice sterile technique when handling microbes. Never have any food or drink at your workstation and always thoroughly wash your hands with disinfectant soap or alcohol before leaving your workstation. Always dispose of used material in a biohazard bag. If none are available, the bacteria should be destroyed with bleach before being disposed of.