You can try a short treatment of your solution in a vacuum oven. If not successful it may help to perform this treatment at a higher temperature (max. 90 C. This is only advisable for approximately neutral solutions of course.) Evaporation losses have to be corrected for, applying mild agitation. It is recommended to perform initial trials at a small scale.

You may be well aware of the fact that sonication of aqueous starch systems will have an impact on their physical and molecular structure.