Abstract:

Adding water to fresh raw milk is a common method in producing adulterated milk. The goal of the present
study was to establish a method for rapidly detecting the added water in milk. For this purpose, milk samples with different
proportions of added water ranging from 0%–14.02% were prepared by adding tap water to fresh raw cow milk. The
conductivities of these milk samples were measured at six temperatures from 10 to 35 ℃. The influence of added water
content and temperature on conductivity was comprehensively analyzed to establish and verify the corresponding model.
The results showed that the conductivity of cow milk deceased linearly with increasing amount of added water but increased
linearly with increasing temperature. The linear equation in two variables, with a coefficient of determination of 0.998 1,
could be used to describe the relationship between conductivity and the amount of added water and temperature. The
absolute error between calculated measured values for the amount of added water in cow milk was −2.15%–2.03%, with an
average of −0.06%, indicating that the amount of added water could be calculated precisely using the model.

Key words: milk, conductivity, amount of added water, temperature, adulteration