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.
Bibliographical noteFunding Information:
We thank Giacomo Mencarini (Università di Pisa) for his contribution to carrying out the NMR experiments. We acknowledge financial support from EPSRC (Ref: EP/J500379/1 ).
We thank Giacomo Mencarini (Universit? di Pisa) for his contribution to carrying out the NMR experiments. We acknowledge financial support from EPSRC (Ref: EP/J500379/1).
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- Amorphous phase separation
- C CP-MAS
- Free volume
- H relaxation times
- Positron annihilation