Over the weekend my roommate had some guests that were staying at our place. I keep my RU in the freezer in a bag that is printed and labeled that says its containing RU and the scientific background. It is also in a white envelope then in a freezer bag. I think possibly that one of the guests while we were out may have replaced it with flour or another white product. How can I safely tell if it is still RU or maybe flour or something else?