Comparing microwave- and water bath-thawed starch-based sauces: Infrared thermography, rheology and microstructure

The purpose of this study was to compare the effects of microwave thawing and water bath thawing on white sauces prepared with two different native starches (potato and corn) and a modified waxy maize starch. The linear viscoelasticity, microstructure and thermographic characteristics of the thawed sauces were analysed and compared with those of freshly prepared sauces. Due to starch retrogradation, the quality characteristics of the native starch-based sauces were strongly affected by freezing and thawing, but these effects were smaller for microwave heating than for heating in a water bath. The water accumulated during freezing tended to diffuse more uniformly in the microwave-thawed sauces, providing a more homogeneous structure than that of the water bath-thawed sauces. It is hypothesized that the shorter heating time in microwave reduces the extent of starch retrogradation during thawing and that local high temperature zones in the microwave may be more effective in the melting of retrograded starch.The dissociated amylose and amylopectin molecules would adsorb the water that is released and help to achieve a more homogeneous distribution of water. The modified starch white sauces were not affected by freezing or by the thawing method.

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