THERMAL AND DYNAMIC-MECHANICAL PROPERTIES OF FROZEN WHEAT DOUGHS WITH ADDED SUCROSE, NaCl, ASCORBIC ACID, AND THEIR MIXTURES

Abstract

The effects of sucrose, NaCl, and ascorbic acid on the physical state of wheat dough at sub-zero temperatures were investigated using Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Analysis (DMA). The DSC thermograms were obtained for annealed samples by scanning from −80 to 10°C at 5°C/min. Added sucrose and NaCl decreased the onset of ice melting of doughs, and they were found at −26°C. Added sucrose and NaCl increased the relative amount of unfrozen water in doughs, while added ascorbic acid had not noticeable effects. DMA measurements were made for annealed samples at a heating rate of 1°C/min from −150 to 10°C. The loss modulus, G″, of DMA showed an α-relaxation (glass transition), two low temperature relaxations (β and γ), and melting of ice in all doughs with added ingredients.

Keywords:

• DSC
• DMA
• Frozen
• Glass transition
• Relaxation
• Wheat dough

ACKNOWLEDGMENTS

This study has been carried out with financial support from the Commission of the European Communities, Agriculture and Fisheries (FAIR) specific RTD program CT97-3609, Use of Wheat Water-Extractable Arabinoxylans (WEA) to Improve Stability of Frozen Doughs and Quality of Bread. The study does not necessarily reflect the Commission's views and in no way anticipates the Commission's future policy in this area. We are grateful to Dr. William MacInnes, Nestlé Ltd., Lausanne, Switzerland, for providing the details of the design of the DMA disc-bending sample holder. The flour and flour analysis were kindly provided by Professor Jan Delcour, Katholieke Universiteit, Leuven, Belgium.