Iodine test as mentioned above, sounds like they werent ripe when picked so this test is even more important, you have to get the right iodine also, not just the stuff you put on your fingers when you get a cut. WVMJ
No you'll be fine with the stuff from the drugstore that you put on cuts, as long as it's actually tincture of iodine. and not some colorless iodine that doesn't stain. This is the same red/orange/yellow staining iodine that I've been using for doing starch testing when checking my mash for beer.
From
http://fruit.cfans.umn.edu/files/2012/08/starch-iodine.pdf
David Bedfords formula for iodine
solution: To prepare the iodine
solution at the beginning of each
season,
purchase a one-ounce bottle
of tincture of iodine at a drugstore.
Pour the entire con-tents into a onepint
spray bottle. Fill the bottle with
water.
The iodine solution is light-sensitive,
so wrap the bottle in aluminum foil.
The solution is poisonous. Label it and
store it away from children and pets.
Slice the apples in half along their
equators. Taste and then set aside
one half of each; spray the cut surface
of the other with iodine solution.
After about a minute, compare the
amount of starch present with a
photographic index. Most apples
grown in Minnesota follow the Granny
Smith chart as they ripen, but you
may find the Red Delicious and Golden
Delicious charts more appropriate for
some varieties.