Phase transition in potato starch–water system I. Starch gelatinization at high moisture level

Optical microscopy, micro-calorimetry (Calvet), FTIR spectroscopy and X-ray diffraction were used to study thermal phase transitions in potato starch–water systems at high moisture level (66–82%). Phase transition in potato starch–water systems depended on the moisture content of the system. At higher moisture contents (e.g. >66%), a first-order transition was observed at about 65 °C, which is associated with gelatinization of starch. The transition was cooperative, involving swelling of starch granules with loss of birefringence and crystallinity. Alteration in the secondary structure and conformation of starch is suggested by the changes around 1020 cm−1 (mainly C–O–H bond vibration) in FTIR spectroscopy. The effect of cultivar, fertilization regime and genetic transformation and storage period on the phase transition behavior of potato starch–water system was also examined.