Iodine and starch test?

Iodine turns blue-black in the presence of starch. Amylose is a form of starch. Iodine solution not in the presence of amylose/starch is yellow. Just putting starch in a 37 degree incubator (Centigrade, I presume, because 37 degrees Centigrade is human body temperature, more or less) would not degrade the starch by itself. Did you also add amylase, an enzyme that breaks down amylose into its component sugars, or possibly saliva, which contains amylase? Amylase only works at or near 37 degrees. If so, the starch was not gone, per se, but converted into sugar molecules which do not react with iodine to form the blue-black color.