Study of pork meat freezing process by infrared thermography

Frozen storage is an important preservation method widely implemented in meat industry. The correct performance of this operation is essential for the maintenance of nutritional value and organoleptic characteristics of meat products intended for retail sale. The development of optimal quality attributes is intrinsically related to the physicochemical phenomena occurred during freezing, particularly to changes in the structural integrity of muscle tissue. Currently, meat industry emphasizes the importance on ensuring an adequate control of temperature and cooling rate to certify the quality and safety through processing. However, this control system is unreliable and useless to know if the meat has undergone undesirable alterations during the freezing stage. To solve these drawbacks, there is a growing tendency to implement non-destructive control methods that allow us a better understanding of the food systems and the processes involved. Among these new emerging non-contact techniques, the infrared thermography has become popular due to its easy handling and its ability to provide useful information at real time. Regarding this, an Optris PI® 160 thermal imager (Optris GmbH, Berlin, Germany), with a spectral infrared range of wavelength λ from 7.5 to 13µm, was used for controlling on line the freezing stage in pork (Longissimusdorsi). Meat samples were frozen from room temperature to -20°C at a cooling rate of 0,1°C/min. K-thermocouples were strategically placed in different regions of the samples and the freezer in order to correct the data registered by the camera. Also, a certified emissivity label of known emissivity (e=0.95) was used as a reference emitter. Furthermore, the structural changes promoted by freezing were analysed. From the results obtained, it was developed a control model to ensure a correct development of the freezing stage in pork.

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