Investigation into the antibacterial properties of mint and garlic.

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Investigation into the antibacterial properties of mint and garlic.


        This experiment is being performed to determine the antibacterial properties of mint and garlic and therefore, which would be the most suitable for use in toothpaste. In order to see if there are any antibacterial properties, a control of distilled water absorbed onto a filter paper disc will be used. Comparisons can then be drawn from the control.


Raw garlic is strongly antibiotic and has a reputation for lowering blood pressure. Allicin is the active ingredient in garlic which has antibacterial properties over a wide variety of infections. Allicin works by inhibiting the enzymes which allow the infections to damage organisms. It attacks the enzymes sulphydryl (SH) group(or thiols), which prevents the enzymes from functioning correctly.

Mint contains a waxy substance called Menthol, This provides mild anaesthetic properties. Due to this it is widely used in lip balms and throat sweets to relieve the pain in the short term. There is however no evidence to support the theory that mint itself has any antibacterial properties. Many studies have found that mint only has mild anaesthetic properties. The antibacterial properties of mint toothpaste is provided by chemicals that are added to the toothpaste and the mint is used as a mild anaesthetic and flavouring agent.

From the evidence above, a hypothesis can be drawn; Garlic will have the most effective antibacterial properties due to the presence of Allicin. Mint should in theory have little or no effect on the bacteria used in this experiment.


  • 1 Sterile Petri dish
  • 4 cloves of garlic
  • Several leaves of mint
  • Sterile nutrient Agar jelly (1 bottle)
  • Escherichia coli (E. coli)
  • Pestle and mortar
  • Sterile syringe
  • Sterile forceps
  • Filter paper discs (5-10mm diameter)
  • Tape
  • Marker pen
  • Incubator set at 52ºC
  • Methylated spirits
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        Methylated spirits is toxic and highly flammable. Therefore great care should be taken to prevent contact with any naked flame or other incandescent material.

        Aseptic technique should be used at all times to prevent contamination of agar jelly or bacteria. All used Petri dishes should be autoclaved to destroy any living organisms and to sterilise the dishes. Aseptic technique is used to prevent microbial contamination. In this case we shall be using flaming sterilisation to prevent aerosols (airborne bacterium). This technique involves flaming the neck of  all the opened bottles, just after opening and just before re-sealing. The work ...

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