Determination of the contents of water and moisture in milk powder

Abstract

According to official methods the moisture content of milk powders is determined by drying techniques and the loss of mass defined as water content. The mass loss, detecting the volatiles evaporated under the applied conditions, is strongly dependent on the drying parameters. An ideal method should be able to determine “free water” without including “bound water” in the result. Two collaborative studies showed that drying methods are not capable of distinguishing between different binding forms of water and only the total water content, measured with Karl Fischer titration, provides results which can be attributed to a defined physical property. Results from two European 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.