For middle school students interested in microbiology, this is sure to be a great science fair project to check out! It addresses the issue of food spoilage; specifically how different spices, naturally found in the environment, can be used as to preserve foods due to the antimicrobial and anti-fungal compounds they contain.
Spices you might explore...
- Vanilla beans
[NOTE: Use the actual spices or explore the effects of the active "preservative" ingredient found in the spice - i.e. carvacrol, which is present in oregano, thyme and pepper; eugenol, which is found in cinnamon, cloves and allspice; vanillic acid, the active ingredient in vanilla beans and coriander, etc.]
If you're looking for an example procedure to help set up your experiment, check out this project from Science Buddies for some inspiration!