Microwave sensing for meat and fish structure evaluation

Monitoring changes in muscle structure during the ageing of bovine meat and quality loss due to fish freezing are major industrial challenges. During ageing, bovine muscle becomes tender through muscle fibre deterioration, and full control of this process is essential. Conversely, degradation of fish muscle, often due to long storage or a freezing cycle, lowers quality. To improve competitiveness, and to respond to consumer quality demand, muscle structure needs to be evaluated in-line. We present here a polarimetric microwave method (10–24 GHz) consisting in free space and contact reflection coefficient measurements using a horn antenna and rectangular probes, respectively. This method is based on the measurement of dielectric properties of tissues parallel and perpendicular to muscle fibre directions. The dielectric properties of structured tissues such as muscles are anisotropic, but during processing structural disorganization reduces this anisotropy. The method is illustrated by the discrimination of fresh and frozen-thawed fish fillets and by monitoring of meat ageing.