The purpose of this thesis was to study the effects of alpha-amylase enzyme on the baking process and bread structure. Alpha-amylase is an enzyme that is naturally found in wheat and rye grain.

Amylase enzymes break the starch in grains to smaller sugar molecules. Smaller sugars are easier for the embryo to utilize for growing to a new plant. The exact concentration of alpha-amylase enzyme varies between each grain or flour batch. These enzymes also display different levels of activity depending on the circumstances. The primary factors are weather conditions during dry-down and the artificial drying method used. The moisture content in grains increases enzyme activity. Heavy rains prevent crops from drying properly. In the worst case, the grains start to germinate before harvest.

A number of baking tests were performed to study the effect of higher enzyme activity on bread structure, bread volume and baking loss. For rye bread it was also tested whether alpha-amylase enzyme alters the rate at which the acidity of sourdough decreases. On the basis of the background literature study, it was known that high enzyme activity catalyses the break-down of starch into smaller sugars. Sourdough baking utilizes the byproducts of microbe metabolism. High enzyme activity thus makes the sourdough acidity decrease faster, because the sugars are available faster for microbes to use. The sourdough tests were performed by varying both enzyme activity and sourdough temperature.

The baking test bread qualities were consistent with literary review in the sensory examination. A low falling number had a negative effect on the quality and structure of rye bread and wheat bread. However, this study did not provide a clear result regarding the connection of the falling number to the rate of acidity decrease in sourdough.

For rye baking, the combined effect of sourdough temperature and low falling number had statistically significant effects on bread volume, baking loss and rate of acidity decrease in sourdough. For wheat baking, a low falling number had significant effects on both baking and bread volume.