A Model for the Structure of Hydroxypropyl Starches

The exponential relation between degree of substitution (DS) and reducing power of pancreatin digests of hydroxypropyl starches, found in an earlier study, is explained by means of a statistical model. The model is based on the assumption that the hydroxypropyl groups are distributed at random over the starch molecules. It is shown that in that case the reducing power of the pancreatin digests is a function of (1 – DS)j. In this equation j is a constant; from the available data its numerical value was estimated to be 5.3. This result is interpreted as an indication that the pancreatic enzymes act only upon α(1→4) glucosidic chains containing five or more glucopyranose units.