ASABE Technical Library - Abstract

Abstract

Three different semi-hard cheese types were investigated with non-destructive ultrasonic methods during two different storage experiments in through-transmission mode. Pulse signal form was used to measure the Time of Flight (TOF) parameter comparing three different calculation methods: setting a threshold value, measuring the time between energy envelope peaks and between the centroids of the envelopes. The comparison showed the different applicability of the methods, including estimation of the acoustic dispersion phenomenon, which is one of the major drawbacks of ultrasonic testing of food materials. In the second experiment, TOF was estimated via cross-correlation based on Fast Fourier Transforms (FFTs) of the input chirp signal and the response signal. The results of this method support the findings of the first experiment. Also, high correlations between signal amplitude vs. storage time and signal energy vs. storage time were found, yielding R² values of 0.93 and 0.99 respectively. A third method was used to estimate storage time from the response spectra using discriminant analysis. 84% correct classification ratio was achieved with a maximum of 91% within-group with the spectrum magnitude values as estimators exclusively. Results showed that the applied methods are suitable for gathering parameters that are corresponding with certain internal properties and quality attributes of cheese.