Microstructural changes of potato cells and starch granules heated in oil

Abstract

A method that mimics the frying operation was implemented to observe microstructural changes in potato cells and starch. Isolated cells were obtained by successive treatments of potato tissue with acid and alkali solutions. Potato cells were heated in oil at a rate of 40 degreesC/min or directly in hot oil (180 degreesC) using a hot stage attached to a light microscope and studied by video-microscopy. Starch granules in cells underwent rapid gelatinization, deformation and compaction into one mass that occupied the whole volume of the cell. After dehydration cells showed a distinctive outer zone and a homogeneous core. Cell walls showed no signs of disruption but at temperatures > 100 degreesC a reduction in cell area occurred. Immersion of cells in hot oil resulted in rapid swelling of starch. Relative projected area increased by 12% after 45 s of heating. Wet isolated starch granules began to expand and gelatinize at 65 degreesC and became disrupted at 120 degreesC. No changes were observed in dry starch granules subjected to a similar treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.