Abstract. This paper presents a novel approach for determining certain material properties from permittivity measurements. It does not rely on physical models and mixture formulas. Instead, the reflection time domain response of the material to a step impulse is evaluated in a narrow time window near the steepest ascent of the pulse. A dedicated time domain spectrometer is introduced, which records the data. Principal components are derived directly from the time domain data. The most significant principal components are used to establish a principal component regression formula for prediction of the required material properties. The viability and accuracy of the method is demonstrated by applying it to measurements of the storage time of some chilled fish samples.