Effect of Freezing Rate and Starch Granular Morphology on Ice Formation and Non-Freezable Water Content of Flour and Starch Gels

Abstract

Ice formation and non-freezable water (W_NFW) of rice flour and tapioca starch gels were studied at two different freezing rates (–10 and –100°C/min) using differential scanning calorimetry. Ice crystal growth was observed in the slow freezing but not in the fast one. Ice melting enthalpies, however, were similar since more ice formed in holding and reheating steps. Melting enthalpy of fully gelatinized systems with water contents ~ 0.50–0.66 was associated to starch composition and granule morphology. Highly swollen tapioca starch gave the lowest enthalpy and the highest W_NFW (0.40 g/g dry starch versus 0.32 and 0.38 g/g dry starch of normal and waxy rice flours, respectively). The further studies revealed that the W_NFW values were associated to swelling power, solubility, and granule morphology.

Keywords:

• Ice formation
• Non-freezable water
• Rice flour
• Tapioca starch
• Granule morphology of starch

Acknowledgments

The authors are grateful to the Tapioca Development Corp. Ltd. for the provision of pre-gelatinized TS.

Funding

This study was granted by the National Metal and Materials Technology Center (MT-B-55-POL-07-519-I).

Additional information

Funding

This study was granted by the National Metal and Materials Technology Center (MT-B-55-POL-07-519-I).