Use of Non-Destructive Ultrasonic Techniques as Characterization Tools for Different Varieties of Wine

Abstract

In this work, we have verified how non-destructive ultrasonic evaluation allows for acoustically characterizing different varieties of wine. For this, a 3.5 MHz transducer has been used by means of an immersion technique in pulse-echo mode. The tests were performed at various temperatures in the range 14-18 °C. The evaluation has been carried out studying, on the one hand, conventional analysis parameters (velocity and attenuation) and, on the other, less conventional parameters (frequency components). The experimental study comprised two stages. In the first, the feasibility of the study was checked by inspecting twelve samples belonging to six varieties of red and white wine. The results showed clearly higher ultrasonic propagation velocity values in the red wine samples. In the second, nine samples of different monovarietal wine varieties (Grenache, Tempranillo and Cabernet Sauvignon) were analyzed. The results show how ultrasonic velocity makes it possible to unequivocally classify the grape variety used in winemaking with the Cabernet Sauvignon variety having the highest values and the Grenache the lowest. In addition, the wines of the Tempranillo variety are those that present higher values of the attenuation coefficient, and those from the Grenache variety transmit higher frequency waves.

Keywords: FFT; ultrasonic attenuation; ultrasonic pulse velocity; ultrasonic transducers; ultrasound parameters; wine.

Figure 1

Picture and diagram of the experimental set-up for the ultrasonic tests.

Figure 2

Progression of the average ultrasonic velocity values (UPV_lr and UPV_cepstrum) obtained through both methods across samples inspected at varying temperatures alongside linear regression fitting between them.

Figure 3

Evolution of mean ultrasonic velocity values (UPV_cepstrum) with temperature for the samples of white and red wine inspected in the initial phase of the study. The green shades have been used for white wines, and the reddish tones have been used for red wines.

Figure 4

Box-and-whisker plots of the evolution of ultrasonic velocity values (UPV_cepstrum) with temperature for each of the monovarietal samples of red wine inspected in the second phase of the study.

Figure 5

Box-and-whisker plots of the evolution of ultrasonic attenuation (α) with temperature for each of the monovarietal samples of red wine inspected in the second phase of the study.

Figure 6

Box-and-whisker plots showing the evolution with temperature of the frequency percentile 75 (FFT75) for each of the monovarietal samples of red wine inspected in the second phase of the study.

Figure 7

Box-and-whisker plots showing the evolution with temperature of the frequency percentile 75 (FFT75) in each of the echoes obtained in the A-scan for each of the monovarietal samples of red wine inspected in the second phase of the study. The color code used is identical to that used in Figure 4, Figure 5 and Figure 6.