The invention provides a process wherein starch and/or a starch derivative can be gelatinised more efficiently by means a thermo mechanical treatment, when a carbohydrate polymer is used comprising aldehyde containing monomer units which comprise one or more aldehyde groups that are derived from one or more a primary alcohol groups. With this process a granulate or other semi-finished product can be obtained that can be shaped to produce an article that has excellent dimensional stability in water. The invention further provides a granulate, a shaped starch product, a food product or a blown starch film comprising such a carbohydrate polymer.