Structural modification on potato tissue and starch using ethanol pre-treatment and drying process

Abstract

• Ethanol modified potato structure and improved water flow. • Drying time was reduced by 56%. • Any change was observed on the starch molecular profile. • Drying caused “scratches” on the starch granule surface. • The pasting and gel profiles showed few changes. This work evaluated ethanol as a pre-treatment to the convective drying of potatoes, focused on obtaining their starch. Potato slices were treated by immersion in ethanol for up to 30 min and then dried by convection (40 °C, 1 m/s). Different treatments were conducted to evaluate the effect of pre-treatment with ethanol and/or drying on the potato tissue and starch structure and properties. Potato microstructure, rehydration capacity, and drying kinetics were evaluated. After pre-treatment, drying, and rehydration, the starch was extracted and evaluated in relation to both structure and properties. Ethanol pre-treatment promoted structural changes on potato tissues and cells: the cells became withered, with thinner walls, lose turgidity, and changed the initial shape becoming more distorted and compacted. These permanent structural modifications impacted the subsequent mass transfer: the drying time was reduced in ∼56%, and the initial rehydration rate increased ∼25%. There were no changes in the starch molecular profile and only minor imperfections in the surface of the granules. The starch pasting and gel properties were only slightly altered by the drying process. In conclusion, drying and its pre-treatment with ethanol can be a simple technology for preserving potatoes focused on starch extraction.