Hey SJLC
I have iodine tested the cinnamon I buy and it does not test positive for starch...
Don't know if brands vary what the put into their ground spices or not... I guess they must do.
The ingredients list traces of celery and mustard???
Thanks though, because it's as well to check these things out.
I did a big spice testing day a while ago and realised that chilli powder and paprika had been likey culprits for me. 
Take care