The enzymic hydrolysis of commercial wheat starch and freshly prepared wheat starch fractions was studied in batch and flow systems. Fresh starch was prepared by wet separation of wheat flour into starch milk and gluten, followed by processing the starch milk using a serially connected hydrocyclone system to produce underflow and overflow streams. The underflow stream consisted mainly of the larger (> 30 mum) granules, while the overflow stream contained only the smaller (< 10 μm) granules. In batch system, the hydrolysis behavior of wheat starch fractions was investigated under the action of Sigma α-amylase (Bacillus licheniformis), either as soon as they were prepared or after spray drying. The two fractions of fresh wheat starch showed different hydrolysis behavior, the difference getting larger as the separation improves. Underflow streams were found to be much more susceptible to hydrolysis than overflow streams, regardless of whether the hydrolysis was carried out right away or on dried samples, and also regardless of whether rinsing was applied. In flow system, dried underflow stream and commercialwheat starch were hydrolyzed using Orbamil-T (Bacillus licheniformis), Orbamil-BHT (Bacillus stearothermophilus), and Sigma α-amylase (Bacillus licheniformis). Hydrolysis of fresh starch was found to be significantly faster than commercial wheat starch. Commercial α-amylase Orbamil-T was found to be almost as effective as the purified Sigma α-amylase.