Ultrasonics in Evaluating Rheological Properties of Dough From Different Wheat Varieties and During Ageing

Abstract

The utility of low‐frequency ultrasonics in evaluating the viscoelastic properties of dough from different biscuit wheat flour qualities was studied. No distinct correlation was found between the ultrasonic characteristic (ultrasound velocity, v) and the rheological characteristics storage modulus, G' (r=0.43), or loss modulus, G″ (r=0.61), when a constant amount of water was added to the dough. Fairly high correlations were obtained between the ultrasound velocity, v, and the rheological measurements G' (r=0.93), G″ (r=0.92) and the phase angle G′ (r=0.81) with variable addition of water, corresponding to the water absorption capacity of the dough. It was not possible to distinguish between hard and soft endosperm biscuit wheat varieties using ultrasonic measurements, whether with a constant or a variable amount of water added. A high negative correlation was obtained between ultrasonic measurements and the amount of water added to the dough (r = ‐0.94), indicating that the amount of water added affected the ultrasonic measurements more significantly than differences in dough structure and rheological properties. The effect of ageing on the ultrasonic characteristics of dough samples was also studied. The ultrasound velocity, v, and storage modulus, G', increased during 40 min ageing. A high correlation obtained between ultrasound velocity, v, and the storage modulus, G' (r=0.97), indicates that ultrasonics may be a valid method of process control of rheological properties during the manufacture of dough.

Probing thermal transitions and structural properties of gluten proteins using ultrasound

“…It is clear from these results that the magnitude of the ultrasonic velocity for the stronger variety (Glenlea) is higher than the weaker one (Fielder) by about 1,000 m/s. Differences in ultrasonic velocity at this frequency for dough samples (rather than wet gluten) have previously been reported [22], with velocities in doughs prepared from harder wheats being greater than those from softer wheats (although differences in velocity were not as pronounced as those reported for gluten samples here). It should also be noted that as the treatment of the gluten was changed so did the magnitude of the ultrasonic velocity, indicating that both NaCl concentration and the cooking process influence the gluten structure that is monitored by the ultrasonic signal propagation.…”

Ultrasonic characterization of fresh yellow alkaline noodles

“…Various research reports have shown that low intensity ultrasonic techniques are sensitive to changes in the mechanical properties of dough due to the entrainment of gas bubble populations varying in size distribution, the use of varying formula levels of water, as well as salts (Létang, Piau, Verdier, & Lefebvre, 2001;Elmehdi, Page, & Scanlon, 2004;Leroy et al, 2008). However, attempts to use ultrasound to discriminate doughs made from different wheat cultivars have shown mixed degrees of success (Alava et al, 2007;Garcia-Alvarez et al, 2006;Kidmose, Pedersen, & Nielsen, 2001).…”

“…However, the same reports have shown that the gas fraction of dough makes difficult to delineate the role played by the dough matrix alone (independently of the gas void fraction) to the overall mechanical properties. Since gas bubbles affect dough mechanical strength (Bellido, 2007;Elmehdi, 2001), it is necessary to account for them in ultrasonic calculations of rheological properties, otherwise ultrasonic characterization of doughs cannot be regarded as unambiguous (Alava et al, 2007;GarciaAlvarez et al, 2006;Kidmose et al, 2001). Since gas bubbles are not central to the texture and quality attributes of noodle doughs it follows that ultrasound may be well suited for studying the textural characteristics of YAN.…”

“…One ingredient that is often overlooked in wheat flour studies (Alava et al, 2007;Garcia-Alvarez et al, 2006;Kidmose et al, 2001) which is responsible for the distinctive structures of bread doughs and noodle doughs is the gas bubble content. For example, the gas bubbles entrained in bread dough during mixing evolve into the gas cells found in the bread crumb and hence they have a direct effect on bread texture and bread quality.…”

“…When sound waves are propagated through bread dough they are strongly reflected and scattered by the gas bubbles due to the large acoustic (impedance) mismatch between these inclusions and the dough matrix. The use of low frequency ultrasound (<100 kHz) has been used to overcome the problem of high attenuation (i.e., loss of signal) in bread dough (Kidmose et al, 2001;Lee, Luan, & Daut, 1992), making it possible to transmit sound waves through this highly attenuating food system. Several reports have exploited the sensitivity of ultrasound to gas bubbles to monitor their presence and growth in bread doughs.…”