Why rate of starch digested was lower per minute at 60 degrees than rate of 40 degrees

The r ate of starch digested was lower per minute at 60 degrees than the rate of 40 degrees because the enzymes responsible for starch digestion (Amylases), have a maximum activity at 40 degrees itself.

After 40 degrees, the enzyme activity starts deteriorating, and thus, the rate of starch digestion also decrease.