The retrogradation of 5, 10, 15, and 25% corn starch gels was measured using differential scanning calorimetry (DSC), rheology, and an array of NMR spectroscopy techniques. During the initial (<24 h) stage of retrogradation, an increase in G′ corresponding to an increase in the number of solid protons participating in cross-relaxation (MOB) was observed for all four concentrations studied. During the latter (>24 h) stage of retrogradation, amylopectin recrystallization becomes the dominant process as measured by an increase in ΔHr for the 25% starch gel, which corresponded to a further increase in MOB. A decrease in the molecular mobility of the liquid component was observed by decreases in 17O T2, 1H DO, and T2A. The value for T2B (the solid transverse relaxation time) did not change with concentration or time indicating that the mobility of the solid component does not change over time despite the conversion of the highly mobile starch fraction to the less mobile solid state during retrogradation.
- Corn starch
- Differential scanning calorimetry
- Nuclear magnetic resonance spectroscopy
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)