Gelatinization and Retrogradation of isolated potato starch and potato flour: Effect of time and storage temperature assessed by LF-NMR

This study employed low-field nuclear magnetic resonance (LF-NMR) to investigate gelatinization and retrogradation of isolated potato starch and potato flour. After gelatinization, the main peak (T₂ b ) of isolated starch shifted from 11.82 to 56.82 ms to 200.34–507.59 ms, whereas in potato flour, T₂ b decreased from 18.62 to 364.72 ms to 12.58–85.88 ms, representing restricted swelling due to non-starch components. During refrigerated storage, isolated starch showed progressive retrogradation (T₂ b = 50.65–160.49 ms after 7 days), while potato flour remained relatively stable, indicating moderation by proteins and fibers. DSC analysis revealed gelatinization temperatures of 62.3–74.0 °C (ΔH = 5.03–5.56 J/g) for starch and 67.1–76.8 °C (ΔH = 8.94 J/g) for flour, correlating with LF-NMR: crystalline melting increased T₂ in starch, whereas restricted swelling in flour shortened relaxation times. Overall, LF-NMR and DSC complementarily reveal that non-starch constituents stabilize water distribution and limit structural reorganization, providing insights into matrix-, temperature-, and time-dependent starch behavior in complex systems. • LF-NMR used to study gelatinization and retrogradation in starch systems. • T₂ profiles revealed distinct behaviors between potato starch and flour. • In potato flour, non-starch components limit water mobility. • T₂ relaxation narrowed over storage, indicating retrogradation. • Refrigerated storage accelerated retrogradation onset.