Freeze-drying changes the structure and digestibility of B-polymorphic starches.

Starch granules both isolated from plants and used in foods or other products have typically been dried. Common food laboratory and industry practices include oven (heat), freeze, and ethanol (solvent-exchange) drying. Starch granules isolated from maize (A-type polymorph) and potato (B-type polymorph) were used to understand the effects of different dehydration methods on starch structure and in vitro digestion kinetics. Oven and ethanol drying do not significantly affect the digestion properties of starches compared with their counterparts that have never been dried. However, freeze-drying results in a significant increase in the digestion rate of potato starch but not maize starch. The structural and conformational changes of starch granules after drying were investigated at various length scales using scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction, FTIR spectroscopy, and NMR spectroscopy. Freeze-drying not only disrupts the surface morphology of potato starch granu...