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How to do an Experiment to see whether we should put Mint or Garlic in Toothpaste.
An experiment to see whether we should put mint or garlic in toothpaste.
Plants, like humans and other animals, are very susceptible to diseases and so have developed their own defence mechanisms against them. Many protect themselves by producing substances that destroy or inhibit the growth of bacteria. This property is known as antibacterial.
This experiment is an easy and practical way to learn about the antibacterial effects of different substances. The main aim of this experiment is to find out whether or not mint or garlic is better for killing bacteria on our teeth.
Of course, this experiment is not limited to just garlic or mint and can be expanded upon to acquire different findings.
Listed below is what you will need and how you will perform the experiment. The experiment is tailored to using any suspected antibacterial substances – not just mint and garlic.
You will need:
· Plant material (e.g. some garlic and mint leaves)
· Pestle and mortar
· Incubator set at 25oC
· Marker pen
· Sterile forceps
· Sterile petri dish
· Paper discs
· 10cm^3 methylated spirits
· An agar plate seeded with bacteria
How to do it
1. First of all, it is necessary to seed(add bacteria) the agar plates using an aseptic technique.
2. Obtain a plant extract by crushing 3g of plant material (e.g. mint leaves) with 10cm3 of industrial methylated spirit and shake it from time to time for 10 minutes. The advantage of using methylated spirits instead of water is that it kills any bacteria that might otherwise contaminate the extract.
3. Next, pipette 0.1 cm^3 of the newly acquired extract solution onto a paper disc.
4. Repeat 1-3 for any other plants that you may want to use. Make sure to make a new separate test disc for each different extract you use (don’t mix solutions).
5. Use a blank paper disc as a control.
6. Place all of the discs into seeded Petri dishes. Placing three discs and a control (and no more) in each Petri dish is advised. Use sterilised forceps to transfer the discs. Mark the sides of the petri dishes with a marker pen so that you can distinguish the different extracts.
7. Tape the lids onto the top of the Petri dishes, making sure not to tape all around it in order to prevent the growth of dangerous anaerobic bacteria.
8. Incubate the plates at 25oC for 24 hours.
9. Measure the diameters of the circles around the different discs using a ruler (without opening the Petri dishes).
10. Record this data in a table.
11. Repeat 1-10 and calculate a mean average of the diameters for each extract.
12. Create a suitable graph (for just 2 extracts like in the case of garlic and mint, a bar graph is sufficient) out of the mean averages attained.
13. Observe the difference in diameters found.
The plant material which resulted in the highest diameter ring around its respective disc was the most antibacterial plant material.
Mint and Garlic
If the disc using garlic extract’s ring of effect has a higher diameter than the disc using mint extract then garlic will be said to be more antibacterial. In this case garlic would be a better substance to put into toothpaste.
Consider however the other good qualities needed in a toothpaste ingredient such as taste, cost and lasting smells before making a judgement.
- Methylated spirit used in the crushing of the plant material is toxic and highly flammable and as such should not be around when there is an open flame (which is used for the preparation and pouring of the agar plates).
- Aseptic techniques must be used throughout the procedures.
- Do not ever open Petri dishes containing growing organisms because these can cause illness.
- Petri dishes must be autoclaved before being thrown away.
- Wash your hands after the experiment just in case you came into contact with disease.