Interactions, organization and dynamics within phase-separated ternary blends of hydrophobically modified starch (HMS), sucrose and water are investigated using solid-state NMR and positron annihilation lifetime spectroscopy (PALS). Antiplasticization of HMS by sucrose is demonstrated by PALS and 1H NMR T1 measurements. Selective solid-state 13C NMR experiments show that a large fraction of sucrose is in molecular contact with HMS even at high sucrose contents, indicating that the HMS-sucrose phase separation is only partial. Sucrose is observed to migrate away from the HMS-rich domains at temperatures that are above the lower Tg, but still below the upper Tg. 1H spin diffusion experiments indicate that phase separation occurs on a nanometric scale, in line with recent theory (Van der Sman, Food Hydrocolloids 87, 360–370 (2019)). We infer that the nanoscale structure of the HMS-rich phase allows for intimate molecular contact between the HMS-rich and the sucrose-rich phases and explains the unusual dynamic behavior.

Antiplasticization and phase behavior in phase-separated modified starch-sucrose blends: A positron lifetime and solid-state NMR study

Martini F.
Primo
;
Geppi M.;
2020-01-01

Abstract

Interactions, organization and dynamics within phase-separated ternary blends of hydrophobically modified starch (HMS), sucrose and water are investigated using solid-state NMR and positron annihilation lifetime spectroscopy (PALS). Antiplasticization of HMS by sucrose is demonstrated by PALS and 1H NMR T1 measurements. Selective solid-state 13C NMR experiments show that a large fraction of sucrose is in molecular contact with HMS even at high sucrose contents, indicating that the HMS-sucrose phase separation is only partial. Sucrose is observed to migrate away from the HMS-rich domains at temperatures that are above the lower Tg, but still below the upper Tg. 1H spin diffusion experiments indicate that phase separation occurs on a nanometric scale, in line with recent theory (Van der Sman, Food Hydrocolloids 87, 360–370 (2019)). We infer that the nanoscale structure of the HMS-rich phase allows for intimate molecular contact between the HMS-rich and the sucrose-rich phases and explains the unusual dynamic behavior.
2020
Martini, F.; Hughes, D. J.; Badolato Bonisch, G.; Zwick, T.; Schafer, C.; Geppi, M.; Alam, M. A.; Ubbink, J.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1056737
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