CHARACTERIZATION OF THE POWER SPECTRUM OF FORCE-DEFORMATION RELATIONSHIPS OF CRUNCHY FOODS

The mean magnitude of the power spectra of the compressive force-deformation relationships of breadsticks, pretzels and zwiebacks, exposed to five levels of relative humidity, was determined at various cutoff frequencies. In all three foods the mean magnitude had a linear correlation with the Fractal dimension of the normalized original force-deformation relationship, regardless of the cutoff frequency. This implies that the jaggedness of the force-deformation curve, which is most probably a manifestation of the material crunchiness or crumbliness, can be quantified by an additional single numerical index, the mean magnitude of the power spectrum. The correlation's independence of the cutoff frequency is an indication that the loss of crunchiness, as a result of moisture sorption, can be expressed in the shape of the whole spectrum and not only in its high frequency region.