Amylase (diastase) is supplied as a cream to white powder. It is a form of alpha-amylase that acts on starch (amylose and amylopectin) and breaks it down to simple sugars such as maltose and dextrins. Many organisms, including humans, use amylase to render dietary starch soluble so it can be absorbed during digestion.
Amylase (diastase) powder has undetectable levels (with benedicts solution) of reducing sugars at a 0.5% solution (w/v), so the progress of the reaction can be monitored in two ways. First, by using the iodine test to check for loss of the starch substrate. Second, by using Benedict's Solution to check for the appearance of reaction product (sugars).
Reducing sugars have a carbonyl group (-CO) that can be oxidised in certain conditions. Examples of reducing sugars include glucose, fructose and maltose. Note, ordinary cane sugar, sucrose, is not a reducing sugar.
Iodine Test (MC26.1)
The iodine test is used to detect the presence of starch, specifically amylose. A solution of iodine in potassium iodide (MC26.1, I/KI, 1.5%/3%) forms an intense blue-black colour when it comes into contact with amylose.
Benedict's Solution (MC4.1)
Benedict's Solution (MC4.1) is based on copper sulphate, CuSO4, which is a clear transparent blue colour in solution. When Benedict's Solution is heated in the presence of a reducing sugar, the sugar is oxidised and the Cu2+ is reduced to Cu+, forming a characteristic red-orange precipitate of Cu2O. A colour change from blue to orange confirms the presence of reducing sugars.
SOURCE: Aspergillus oryzae