Assessing the use of dielectric spectroscopy to analyse calcium induced compositional and structural changes in a model cheese

The functional properties of a food are determined by the composition and arrangement of the components (the microstructure). In general as the microstructure of a food changes, the dielectric properties of the food change as well. Cheese is an excellent example of a food system which undergoes significant structural rearrangement both during shelf life (maturation) and in applications involving heating. The purpose of this study was to see if dielectric spectroscopy could be used to assess the microstructure of cheese with a view to predicting its functionality. The first task was to create a model cheese system where the composition could be systematically varied and the resulting changes in dielectric properties measured. We were also interested in how the dielectric properties (and thus the arrangement of components) changed with temperature. We developed a model system and samples were prepared with varying levels of calcium. We then measured the dielectric properties over a frequency range of 200 MHz to 1.3 GHz and between the temperatures of 5 and 85 °C. The samples were also examined using a confocal laser scanning microscope as well being subjected to texture profile analysis. We found that the dielectric constant and dielectric loss factors decreased as frequency increased. The dielectric properties were also found to be temperature dependent. The texture of the system was influenced by the addition of calcium which influenced the emulsification. The results from this initial study support the concept of dielectric spectroscopy as a tool for studying the microstructure of cheese. This suggests that dielectric spectroscopy could aid in the development of a better understanding of changes occurring in food systems. The next stage of this study will investigate the changes to the dielectric properties during cheese maturation as well as examining aspects of component mobility within cheese.