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Using ultrasound to characterize fresh yellow alkaline noodles

Low-intensity ultrasound

Traditionally, noodle manufacturers have used sensory panels to assess noodle texture. Sensory panels are groups of experts who assess the taste, smell or feel of products. Using a sensory panel is inadequate for quality control purposes in a high-throughput mechanized factory environment.

Low-intensity ultrasonic techniques have been used to learn about the material characteristics of a product for years (Povey, 1997). In this technique:

  • A sound wave is transmitted through a material.
  • The interaction of the wave with the material is quantified in terms of ultrasonic velocity and attenuation.

The researchers related the ultrasonic parameters to the mechanical properties and microstructure of the noodles. They used mathematical theory describing wave propagation in model food systems that are structurally similar to noodles (Bloksma and Bushuk). Using a wide range of ultrasonic frequencies it would be possible to probe structures in the food material with different length scales (Elmehdi, 2001; Bellido, 2007; Leroy et al., 2008), though at this initial stage a single frequency of 50 kHz was used.

Low-intensity ultrasound does not change the properties of food material, even though enough energy is transmitted to capture the properties of the food material. In addition, it permits probing opaque materials such as dough, unlike light scattering or other light propagation-based techniques.

Even though low-intensity ultrasound is potentially useful in a manufacturing environment, the food industry has not made much use of it. Currently, the industry does not use low-intensity ultrasound to monitor the quality of wheat-based products (Povey, 1997; Scanlon, 2004). Previous studies by other researchers have found that low-intensity ultrasonic techniques are sensitive to changes in the mechanical properties of dough caused by:

  • The presence and growth of gas bubbles of various sizes during fermentation
  • The use of various levels of water and salts (Létang et al., 2001; Elmehdi, Page and Scanlon, 2004; Bellido, 2007; Leroy et al., 2008).

Attempts to use ultrasound to see differences between doughs made from different kinds of wheat have shown mixed degrees of success (Kidmose, Pedersen and Nielsen, 2001; Alava et al., 2007; Hatcher et al., 2008b).