According to official methods the moisture content of milk powders is deter
mined by drying techniques and the loss of mass defined as water content. T
he mass loss, detecting the volatiles evaporated under the applied conditio
ns, is strongly dependent on the drying parameters. An ideal method should
be able to determine "free water" without including "bound water" in the re
sult. Two collaborative studies showed that drying methods are not capable
of distinguishing between different binding forms of water and only the tot
al water content, measured with Karl Fischer titration, provides results wh
ich can be attributed to a defined physical property. Results from two Euro
pean collaborative studies are employed to evaluate three different drying
techniques and Karl Fischer titration. Adsorption isotherms of skimmed milk
powder at different temperatures were used to calculate the isosteric heat
of sorption.