A student investigated the hydrolysis of starch by the enzyme amylase. In one trial, the student incubated a sample of amylase at 85 ∘C85\text{ }^\circ\text{C}85 ∘C for 15 minutes before mixing it with the starch solution. After a further 10 minutes, the mixture was tested with iodine solution, which immediately turned blue-black, indicating that no starch had been broken down.
Explain why no starch was hydrolysed by the amylase that had been heated to 85 ∘C85\text{ }^\circ\text{C}85 ∘C.
