Laser induced breakdown spectroscopy based diffusion modelling in cheese matrix

In the cheese industry, mass transfer of small solutes like salt during brining and ripening is extremely important for the quality of final products. In general, effective diffusion coefficient values have been reported in the studies using destructive concentration profile methods. This study aims to monitor NaCl diffusion in cheese by using laser induced breakdown spectroscopy (LIBS) as a nondestructive method to fulfill the requirement of measuring mass transfer properties of solutes in microscopic size complex heterogeneous structures. To this end, spherical shaped white cheese samples were brined in 16% salt solution for 5–210 min and overnight, and Na emission lines were monitored by scanning the cross-section of each sample at 30 points on the radial axis. As was expected, increasing brining time decreased the concentration difference between the center and edge of the cheese samples. Experimental results were fitted to Fick's Diffusion Equation. It was observed that NaCl distribution became uniform and equal at different locations of the cheese sample after 13.8 h. All these results have demonstrated that LIBS can be utilized for optimization of the brining conditions of cheese. Although the use of LIBS in this study was limited to parameter optimization, it can also be applied for real time monitoring of food processes due to its rapid and continuous measurement mode.