- If you are not sure your pears or apples are unripe, test one using the staining procedure outlined below before continuing.
- Label the bags, numbers 1-8. Bags 1-4 will be the control group. Bags 5-8 will be the test group.
- Place one unripe pear or apple in each of the control bags. Seal each bag.
- Place one unripe pear or apple and one banana in each of the test bags. Seal each bag.
- Place the bags together. Record your observations of the initial appearance of the fruit.
- Observe and record the changes to the appearance of the fruit each day.
- After 2-3 days, test the pears or apples for starch by staining them with the iodine stain.
- Dissolve 10 g potassium iodide (KI) in 10 ml of water
- Stir in 2.5 g iodine (I)
- Dilute the solution with water to make 1.1 liters
- Store the iodine stain solution in a brown or blue glass or plastic bottle. It should last for several days.
- Pour the iodine stain into the bottom of the shallow tray, so that it fills the tray about half a centimeter deep.
- Cut the pear or apple in half (cross section) and set the fruit into the tray, with the cut surface in the stain.
- Allow the fruit to absorb the stain for one minute.
- Remove the fruit and rinse the face with water (under a faucet is fine). Record the data for the fruit, then repeat the procedure for the other apples/pears.
- Add more stain to the tray, as needed. You can use a (non-metal) funnel to pour unused stain back into its container, if you wish, since it will remain 'good' for this experiment for several days.
