Amylases work well at 150-155 degrees. If you get too much higher temp wise it will be destroyed by heat. Alpha type does the initial break down. If you want to really break it down further wait an hour and add some beta amylase to obtain the highly fermentable sugars. To check you results you can do a simple starch/iodine test. With all the un-malted rice used in non traditional beers today this is a common procedure. If a brew supplier doesn't have it, most wine supply places do. I have some liquid enzymes that have manufacture directions for 120 cc / 500gal, so it doesn't take a whole lot.