Yes iodine test. If it turns inky black it is starchy. Iodine test isn't quantative though so you can't really base it on how dark.
One caveat though. Amylopectin starch turns a brownish purple. Amylose starch turns blue black. Amylose starch is what made me sick when I was still starch sensitive. Amylopectin however was safe for me (ie glutinous rice)
