Milk Classification and Water Adulteration Detection by TD-NMR and Dielectric Spectroscopy

Abstract Milk is one of the most widely consumed staple foods worldwide. Its increasing commercial importance both increases the need for quality classification and creates a breeding ground for fraudulent practices, such as adding water to dilute. In this work, some milk varieties, including raw (unheated), skimmed, semi-skimmed, and fat (whole) milk, as well as boiling raw milk, were analyzed using the Time Domain Nuclear Magnetic Resonance (TD-NMR) methodology in parallel with the Microwave (MW) dielectric method. The study also examined the effects of adding water to certain kinds of milk. Spin lattice (T 1 ) and spin–spin (T 2 ) relaxation times and dielectric permittivity constants Ɛ 1 and Ɛ 2 were used to classify milk, and the Inverse Laplace Transform (ILT) method was used to examine these relaxation times further. Furthermore, the effects of temperature categorization on milk were examined using temperature-dependent T 1 and T 2 measurements. As a result, the relaxation times of different types of milk are listed from longest to shortest: skimmed milk, raw milk, semi-skimmed milk, fat (whole) milk, and raw milk (boiled). It was found that T 1 and T 2 values increased with the increase in temperature. And also, skimmed milk has a greater Ɛ 1 value compared to fat (whole) milk. Furthermore, it has been observed that adding water to milk increases the dielectric constant (Ɛ 1- Ɛ 2 ) as the water concentration increases. Overall, our results demonstrate that the TD- NMR and MW approach is a sensitive and efficient method for identifying various milk kinds and detecting the presence of water adulteration.