Dan Solarek, AkzoNobel Surface Chemistry, R&D Americas.

Starch is a natural polymer of α-D-glucose that is commercially extracted on a large scale from grains, roots and tubers. Conventional hybrid breeding offers additional functional starches with one plant source. For example, waxy maize produces 100% amylopectin, a highly branched, high molecular weight starch polymer that has good stability when solubilized in water.

Altering the molecular weight and reacting a small amount of hydrophobic substituent groups onto the starch conveys surface activity. The resulting modified starches can stabilize oil-in-water emulsions. The hydrophobic groups anchor the starch to the oil/water interface. The starch polymer forms a thick, steric, protecting layer around the oil droplets that works to prevent phase separation.

When the starch is tuned to particular oily actives, long-term emulsion stability is possible. The emulsion can be applied by spraying or coating and the film-forming and adhesive properties of the starch polymer will attach the active to a substrate after drying. The starch formulation can be adjusted to form a glassy matrix that encapsulates an oily active upon spray drying. The powder typically has a high (at least 50%) loading of oil. Starch encapsulation of fragrance provides retention during processing and storage stability in formulations. ALCOCAP® 300 is a particularly effective starch for efficiently encapsulating fragrance. Difficult to handle, viscous, oily, or wax-like materials (for example, emollients) can be converted to free flowing powders for easier use / formulation. Release from the starch matrix is achieved by re-wetting, friction and, sometimes heat.

AkzoNobel’s BU Research group of the Surface Chemistry Business Unit can match the right starch to an active and, when necessary, modify the starch for optimum performance. There is good experience developing final formulated emulsions or encapsulated powders for customers.