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Somogyi Tamás

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Somogyi Tamás
Variation of Electrical Impedance Parameters of Dry Crops during Soaking

Aug 29 - kedd

15:30 – 17:00

I. Poszterszekció

P25

Variation of Electrical Impedance Parameters of Dry Crops during Soaking

Tamás Somogyi, Eszter Vozáry and Viktória Zsomné Muha

Hungarian University of Agriculture and Life Science, Institute of Food Science and Technology

Department of Food Industrial Measurements and Control

When processing nutritionally important dry pulses such as beans, soaking is one of the most important preparatory steps. As this process is relatively time-consuming. However, this long soaking time can be reduced by ultrasound.

The experiments were performed on red kidney beans (Phaseolus vulgaris cv. Rampart). Prior to the actual sample preparation, beans were manually sorted into four groups according to their size (S - small ≤ 13 mm; M - medium = 13 - 15 mm; L – large = 15 - 17 mm; X - extra-large ≥ 17 mm).

For the ultrasound treatments we used an ultrasonic bath (HBM Machines, The Netherlands). The treatments applied were performed at 40 kHz 300 W at 20 °C.

The magnitude and phase angle of the impedance of the beans were measured in the frequency range of 30 Hz - 30 MHz with an HP4284A and HP4285A precision LCR meters at a measuring voltage of 1 V in an HP16451 B test fixture. To achieve a good electrical contact, an ECG electrically conductive gel was placed between the bean shell and the electrode.

As the soaking time increased, the magnitude of the impedance decreased, which may indicate that the increased water content reduced the viscosity and thus increased the mobility of the charges, resulting in a decrease in resistance and impedance.

This reduction is also clearly visible in the ultrasonic treatments compared to the control samples.

The phase angle spectrum shifted towards lower frequencies, which in turn may be a result of the destructive effect of ultrasound. The effect of the treatments shifts the minimum point around 31 kHz towards lower frequencies. The longer the soaking time, the lower the impedance value and the more the ultrasound-induced structure damage was well detected. These suggest that it may be possible to qualify the structural condition of the soaked dry structures.