Fresh scallop shell opening method and parameter optimization based on infrared radiation

A shell opening has been the first step for the high-quality shellfish in fresh scallop processing. Most traditional processing, such as manual, mechanical, and steaming, can cause some serious damage to the shellfish. In this study, a novel approach was proposed to open the shell using infrared heating, where the surface temperature of the shell generally determines the opening performance. Correspondingly, a mathematical model was established to predict and control the shell surface temperature distribution during processing. Among them, the infrared heating device consisted of two infrared tubes and a trapezoidal lampshade. The radiation energy of the infrared tube was divided into two parts by the lampshade: the direct radiation of the lamp tube, and the indirect radiation of the lampshade. Therefore, a specific mathematical model was also established for the heat flux density distribution during heating, according to the density of view factor under the two radiation states. As such, the sum was obtained as the total heat flux density distribution on the shell surface. The heat flux ratio was first defined as the proportion of the heat flux of the Adductor Muscle Scar (AMS) region to the total heat flux of the shell surface, which was taken as the index to measure the heating performance during processing. A MATLAB platform was used for the numerical simulation under various conditions using the model, thereby clarifying the influence of the lampshade inclination angle, lampshade side width, and lamp tube installation height on the heat flux ratio. Response surface analysis was also carried out to verify the influence of three parameters on the heat flux ratio under the interaction. It was found that there was a more concentrated distribution of heat flux in the AMS region when the angle of the lampshade was in the range of 30°-60°, the side width of the lampshade was in the range of 30-50 mm, and the height of the lamp tube was in the range of 60-80 mm. The contribution proportion rate of heat flux was also gained to evaluate the performance under the three heating parameters. An optimal combination of parameters was achieved as follows: the angle of the lampshade was 30 °, the side width of the lampshade was 40 mm, the installation height of the lamp tube was 60 mm, and the heat flux ratio was 0.584 9. In this case, the temperature distribution on the surface of the scallop was then predicted, where the heat flux model was taken as the boundary condition. The numerical simulation results show that there was a relatively concentrated temperature distribution in the vicinity of the scallop column, and the temperature at a single point increased linearly with time. There was also a larger slope of the temperature rise curve, with the increase of lamp power during heating. Meanwhile, an infrared heating test was performed on the 100 fresh scallops. The test results showed that: the shell opening efficiency reached 15 per minute, the opening temperature was maintained at 85-98 ℃, the internal skirt tissue shrinkage rate was low, the shellfish quality was high, and the sensory score of opening effect was 97 points, indicating the temperature measurement in better agreement with the simulation, thus verifying the effectiveness of the model. Consequently, the temperature distribution model can provide a theoretical basis for the application of infrared heating in automatic scallop processing.