doi:10.1016/j.biosystemseng.2006.09.005
Copyright © 2006 IAgrE Published by Elsevier Ltd.
Moderate Electric Field Treatment of Sugarbeet Tissues
References and further reading may be available for this article. To view references and further reading you must
purchase this article.
N.I. Lebovka1, 2, 
, M. Shynkaryk1, 2 and E. Vorobiev1, 
,
1Departement de Génie Chimique, Université de Technologie de Compiègne, Centre de Recherche de Royallieu, B.P. 20529-60205 Compiègne Cedex, France
2Institute of Biocolloidal Chemistry named after F.D. Ovcharenko, NAS of Ukraine, 42, blvr. Vernadskogo, Kyiv 03142, Ukraine
Received 26 January 2006;
accepted 27 September 2006.
Available online 28 November 2006.
The effects of thermal and moderate electric field (MEF) treatment on the damage of sugarbeet tissue were discussed. The activation energy ΔUT was estimated as 170 kJ mol−1 using the temperature dependences of the characteristic thermal damage time within the temperature interval 50–70 °C. The temperature dependences of electrical conductivity were measured for the maximally damaged and intact sugarbeet tissues; these data were used for estimation of the conductivity disintegration index at different MEF treatments. The results evidenced that the electrically stimulated damage of a sugarbeet tissue occurs even at a rather small electric field strength E of 20 V cm−1 if treatment time is large enough (t≈1 h). The energy consumption caused by MEF-treatment is mainly related to temperature elevation inside the tissue and noticeably decreases with increasing electric field strength E. MEF-treatment experiments in the aqueous media reveal the dependence of damage efficiency on sample orientation with respect to the external electric field.
Notation
- b
- coefficient
- C
- specific heat capacity of tissue, J kg−1 K−1
- D
- thermal diffusivity, m2 s−1
- d
- diameter of a sample, cm
- E
- electric field strength, V cm−1
- h
- height of a sample, cm
- I
- electric current, A
- n
- number of pulses
- R
- universal gas constant, 8·314 J K–1 mol–1
- r
- electrical resistance, Ω
- T
- temperature, °C
- t
- treatment time, s
- tp
- pulse duration, s
- U
- applied voltage, V
- W
- electric energy input, kJ kg−1
- Z
- electrical conductivity disintegration index
- α
- temperature coefficient of the electrical conductivity, °C−1
- Δt
- pulse repetition time, s
- ΔUT
- activation energy, kJ mol−1
- ρ
- density, kg m−3
- σ
- electrical conductivity, S m−1
- τ
- characteristic damage time, s
- τD
- time of thermal diffusion, s
Subscripts
- i
- intact
- d
- damaged
- o
- initial
- s
- sample
- T
- thermal
- w
- water
- ∞
- limiting
Fig. 1. Schematic representation of the experimental arrangement; LCR, inductance, capacitance and resistance; AC, alternating current; PEF, pulsed electric fields
Fig. 2. Chambers for the treatment of: (a) one tissue cylinder; (b) two tissue cylinders in tap water with perpendicular and parallel orientations with respect to the external field (E)
Fig. 3. Arrhenius plot of the characteristic thermal damage time (τT) versus inverse temperature 1/(T+273·15) for potatoes; symbols are the experimental data, dashed line is the result of their linear least mean square fitting, the error bars represent the standard data deviations; insert shows the disintegration index (Z) versus time of thermal treatment (t)
Fig. 4. Effect of temperature (T) on the electrical conductivity (σ) for the maximal damaged and intact sugarbeet tissues: (a) damaged; (b) intact; symbols are the experimental data; dashed lines are the result of their linear least mean square fitting; the error bars represent the standard data deviations
Fig. 5. Typical dependence of the electrical conductivity of an ohmically treated sugarbeet tissue (σ) versus temperature (T) inside the sample (bottom axis) and the time of treatment (t) (upper axis) at the electric field strength E=60 V cm−1; dashed lines show the temperature dependency of conductivities (σd and σi) in the totally damaged and intact tissues, respectively
Fig. 6. Conductivity disintegration index (Z) versus temperature (T) of the moderate electric fields treated sugarbeet tissues at different electric field strengths (E); the initial temperature was (a) 15 °C and (b) 40 °C; the error bars represent the standard data deviations; 
, E=40 V cm−1; 
, E=60 V cm−1; ■, E=100 V cm−1
Fig. 7. Typical optical microscopy image of an intact sugarbeet tissue
Fig. 8. Electrical energy input (W) for AC treatment at different electric field strengths (E), estimated for the 50% level of damage (disintegration index Z=0·5) at two different initial temperatures (To): 
To=15 °C; 
, To=40 °C
Fig. 9. Temperature elevation (T−To) versus product (tE2) for the moderate electric fields treated sugarbeet tissues with the initial temperature To=15 °C and electric field strength (E): 
, E=60 V cm−1; 
, E=100 V cm−1; 
, averaged data for the maximally damaged tissues at E=40–80 V cm−1; dashed line shows the predicted (T−To) versus (tE2) curve, calculated from Eqn (5) for an intact sugarbeet tissue; t is a treatment time
Fig. 10. Conductivity disintegration index (Z) and the total treatment time (t) versus electric field strength (E) for the moderate electric fields treated sugarbeet tissues of parallel (||) and perpendicular (
) orientation inside the tap water (Fig. 2b); the error bars represent the standard data deviations
Fig. 11. Difference of temperatures inside the sample (Ts) and water (Tw) versus the water temperature (Tw) for (a) ohmically heated intact and (b) maximally damaged sugarbeet tissues; the data are presented for samples of parallel (||) and perpendicular () orientations with respect to two values the external field strength (E); the error bars represent the standard data deviations; ■, E=40 V cm−1;
, E=60 V cm−1
Corresponding author. Tel.: +33 344234423; fax: +33 344231980.
Abstract
Purchase PDF (904 K)
E-mail Article
Add to my Quick Links
Cited By in Scopus (2)
Purchase PDF (554 K)
