Filament hygrometer for water activity measurement: interlaboratory evaluation

A method is presented for measuring water activity (aw) of foods with a filament hygrometer. An interlaboratory evaluation carried out for the Nordic Committee on Food Analysis demonstrated that measurements can be made with a repeatability and reproducibility of 0.005 and 0.010 aw, respectively. The critical parameters of aw measurements are defined and discussed in relation to the accuracy and reproducibility required. The need for strictly standardized procedures for maintenance of the equipment, sample treatment, calibration, and measuring is emphasized.