Study of dielectric behavior of cow’s milk with water adulteration

The dielectric properties of raw cow’s milk and its adulteration with varying water contents (WC) were investigated using a Vector Network Analyzer (VNA) operating in the frequency range of 200 MHz to 20 GHz. The measurements were carried out at a constant temperature of 20°C, focused on determining the dielectric constant (ε’), dielectric loss (ε”), Loss tangent (tanδ) and conductivity (σ’) of the water-adulterated milk samples. It was observed that ε’ exhibited a decreasing trend with an increase in frequency, spanning from 200 MHz to 20 GHz, for all samples. Furthermore, the study shows that ε’ demonstrated an increasing trend with an increase in WC in milk, for all samples at a specific frequency. This suggests that the dielectric constant is mainly influenced by water content in the milk and highlights the sensitivity of the dielectric properties to variations in milk sample composition. ε” displayed an increase with rising WC in milk for frequencies greater than 4.5 GHz. However, at frequencies less than 2 GHz, ε” exhibited a decreasing trend with an increase in WC in milk. σ’ of the samples exhibited a consistent increase with an increase in frequency across all samples. Moreover, at a specific frequency, the conductivity was observed to rise with an increase in WC in milk. The value of tanδ for the milk samples at 1.3 GHz shows linear decreasing trend with the increase in water content in the milk, which can be used to directly predict the % of additional water content in the milk.