Starches

Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds arranged in the most diverse ways. This polysaccharide is produced by most green plants for energy storage. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods like potatoes, maize (corn), rice, wheat, cassava (manioc), barley, etc...

But before talking about enzymes we need to understand what is the starch in the malt and what are the sugars we want to produce.

Gelatinization

Starch granules are insoluble in cold water and will absorb only little water. They form a suspension that quickly settles once agitation stops. As the water is heated (>50°C) more and more water is absorbed and the granules start to swell. The water absorbed during this process can be up to 30 times the weight of the starch granule. This uptake of water initially happens within the amorphous growth rings. At this point the granule starts to leach amylose and the crystalline layers break open and separate from the starch granule as gelatinous sheets. At this point the crystalline structure is lost and the process becomes irreversible with respect to the shape of the starch granule. The starch granule has gelatinized.

The starch is gelatenized to become water soluble.

For starch found in barley and malt the gelatinization happens above 140ºF (60ºC). Other starches (rice for example) gelatinizes only above 194ºF (80ºC) and requires boiling before it can be converted by enzymes.