Microstructural changes of potato cells and starch granules heated in oil

A method that mimics the frying operation was implemented to observe micros tructural changes in potato cells and starch. Isolated cells were obtained by successive treatments of potato tissue with acid and alkali solutions. P otato 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 gela tinization, deformation and compaction into one mass that occupied the whol e volume of the cell. After dehydration cells showed a distinctive outer zo ne 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 b egan to expand and gelatinize at 65 degreesC and became disrupted at 120 de greesC. No changes were observed in dry starch granules subjected to a simi lar treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.