Cold enzyme hydrolysis of wheat starch granules

Three alpha-amylase enzymes were used to hydrolyze wheat starch granules suspended in water below the gelatinization temperature. The rates of hydrolysis were determined at various temperatures, pH, enzyme and starch concentrations. Barley amylase was found to be the "best" enzyme when used at pH 4.5, 45 degrees C and starch and enzyme concentrations of 30 and 8 mg/mL respectively. It was found that under these conditions, 98% of the starch granules were hydrolyzed in 3 hours, the same amount of time used in the industrial cooking process of soluble starch. Starch particles were observed to be attacked at specific points on the surface and then hydrolyzed from the inside-out. Some granules were hydrolyzed at a very fast rate with a first order rate constant estimated to be 40 h(-1); but most granules were hydrolyzed slowly according to the Michaelis-Menten model and the best fit parameters were found to depend on enzyme type, pH and temperature.