RETROGRADATION OF POTATO STARCH AS STUDIED BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Retrogradation kinetics for a potato starch-water system (10% w/w gel) was monitored by Fourier Transform infrared spectroscopy and compared with waxy maize starch. The spectra showed the C-C and C-O stretching region (1300-800 cm(-1)) to be sensitive to the retrogra dation process. A multi-stage process was observed during the retrogradation of potato starch and characterized as the formation of short- and long-range order. The first stage was characterized as the formation of helices and the fast formation of crystalline amylose regions. The second stage was described as the induction time for amylopectin helix aggregation. Stage three was described as the helix-helix aggregation and the crystallization of amylopectin. The overall-first order calculated rate constant of potato starch was (9.6+/-1.4) 10(-3)h(-1). The calculated rate constant were in agreement with the known difference in retrogradation kinetics of waxy maize and potato starch. The effects were explained by the differences in retrogradation rate of amylopectin and amylose. Potato starch consists of amylose as well as amylopectin. Whereas amylose crystallization occurs within a few hours, amylopectin crystallization is slow and lakes a few weeks.