Science Buddies: "Ask an Expert"

Hey, I saw the One Bad Apple experiment in the science buddies project guide and am doing it. I'm using pears. When I tested the pears for ripeness (before I've experimented with the bananas), according to the macintosh apples ripeness guide provided they rated a 9- as over-mature as it gets. But I am positive they are unripe. For one, they are definitely green. Also, I found out that if you squeeze a pear by its neck and it's hard, the pear is unripe. These are unripe. I know the iodine solution has not expired because I tested it with a banana the same day and it registered correctly. Please help!!! Is there a pear ripeness guide? Does the test work with pears (I noticed the project guide says to use the ripeness chart with "apples" mentioned specifically) or do they need to be measured with the ways I mentioned earlier? Are there any images on science buddies with pears that have the iodine stain on them? Thank you for your time!

Good afternoon,
I'm not sure how different this protocol is from the one you've been using but I attached one I read below:
"Starch-iodine Testing: As fruit mature, starch is converted to soluble sugars. Iodine turns starch black; therefore, an iodine solution can be used to determine the amount of starch remaining in the fruit. A solution of 10 grams of potassium iodide and 2.5 grams of iodine in 1 liter of water should be used. During mixing and use of this solution, make sure the area is well ventilated—iodine fumes are toxic. This solution should be stored in a plastic or glass container as it is corrosive to metals. Providing the container is well stoppered, the solution will keep for long periods of time. Fruit should be cut in half through the equator and the cut surface dipped or sprayed with the iodine solution from a plastic spray bottle. The starch patterns will develop in approximately 1 minute. As fruit mature, starch clears from the core first, followed by the cortex. These patterns will be slightly different for each variety. The starch index at which fruit should be harvested depends on the intended length of storage. As a guide, fruit destined for storage should be harvested at a starch-iodine index of 4 to 5, whereas fruit for immediate sale should be harvested at an index of 6 to 7. As with any indicator of fruit maturity, the starch-iodine index should be used in combination with other maturity tests"


It sounds like there is some inherit variability in the pears, so it might have to do with the location your running the test. That's weird the chemical already worked with the banana though. I hope this helps.

Do you mean the location as in the area where I live? or just my house? Like, would it work if I took it to, say, my school or something?