Abstract: Protease enzyme impurities contained in bacterial .alpha.-amylase enzyme preparations are inactivated by a mild heat treatment in the presence of a protective material. Useful protective materials include calcium and starch hydrolysates such as corn syrup. The protease-free .alpha.-amylase can then be used to solubilize starch materials by various granular starch and conventional processes. Hydrolysates obtained contain significantly less soluble protein than those prepared using untreated .alpha.-amylases. A preferred .alpha.-amylase enzyme preparation is one derived from a Bacillus licheniformis microorganism.