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Evaluate the properties of dough using a range of ultrasonic frequencies.

Low-intensity ultrasound is sensitive to the presence of bubbles within dough's viscoelastic matrix. This sensitivity makes it useful as an analysis tool for a material in which bubbles largely determine the gas cell structure in the resulting products.

Canadian researchers believe that ultrasonic measurements over a wide frequency range can provide new insight into the structure, properties and dynamics of dough systems. They found that ultrasound can provide new information on dough properties, making it possible to better predict the gas cell structure of bread products.

In experiments, the scientists created dough samples, without yeast, by mechanically mixing flours of varying dough strength. Samples were also mixed under vacuum conditions to create doughs that contained very few bubbles.

Monitoring the changes in ultrasonic velocity and attenuation that occur during fermentation makes it possible to see how fermentation affects dough matrix properties and the expansion of the gas cells within the dough matrix. The scientists analyzed the properties of the samples using a series of transducers that covered a wide frequency range, from 50 kHz to 20 MHz. At low frequencies, the doughs made from stronger flours exhibited higher ultrasonic velocities. At low frequencies, ultrasonic attenuation was large, but diminished with time. There were substantial changes in ultrasonic velocity, accompanied by small changes in frequency-Such observations were not apparent in vacuum-mixed doughs, indicating that these features are bubble-dependent. At higher frequencies, attenuation rose quadratically along with frequency in both air- and vacuum-mixed doughs, but changes in ultrasonic velocity were minimal.

It is apparent from these results that the ultrasonic spectrum of dough is comprised of three distinct regions. In the low-frequency region, the composite properties of the dough matrix and bubbles differ according to the strength of the flour used. In the intermediate region, bubble resonance dominates, with time-dependent changes in attenuation arising from the ripening of bubbles within the dough. In the high-frequency region, modeling of the dough matrix reveals a structural relaxation in the nanosecond time range that is likely associated with conformational changes in gluten proteins.

Further information. Martin G. Scanlon, Department of Food Science, University of Manitoba, 224 Ellis Building, Winnipeg, Manitoba R3T 2N2, Canada; phone: 204-474-6480; fax: 204-474-7630; email:
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Publication:Emerging Food R&D Report
Date:Jun 1, 2011
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