This study is devoted to solid–liquid extraction from carrot samples subjected to pulsed electric fields (PEF) of different energy levels. Aqueous extraction of solute from carrot samples prepared in the forms of disc or slices (coarse and fine) was conducted at room temperature with and without agitation. A two-exponential kinetic model corresponding to the two-stage extraction (rapid washing and slow diffusion) described successfully the experimental data. For the studied carrot samples, the solute yield increased with the increase in energy level up to a threshold value of 9 kJ/kg. Furthermore, the increase in stirring speed up to 250 min⁻¹ enhanced extraction kinetics. Finally, fragmentation of carrot particles increased the solute yield obtained during the washing stage of extraction.

Notation

c

solute concentration in the solution at any time during the extraction process, g [solubles]/100 g [juice]

c₀

solute concentration of fresh sugar beet juice (initial solute concentration), g [solubles]/100 g [juice]

c^*

dimensionless solute concentration in the solution at any time during the extraction process

c_d

equilibrium solute concentration in the solution due to the diffusion process, g [solubles]/100 g [juice]

dimensionless equilibrium solute concentration in the solution due to the diffusion process

c_w

equilibrium solute concentration in the solution due to the washing process, g [solubles]/100 g [juice]

dimensionless equilibrium solute concentration in the solution due to the washing process

c_∞

total equilibrium solute concentration, g [solubles]/100 g [juice]

d

distance between electrodes, mm

E

intensity of pulsed electric field, V/cm

I

amplitude of electric current strength, A

k_d

rate constant for the diffusion process, min⁻¹

k_w

rate constant for the washing process, min⁻¹

L

extract volume, m³

m

mass of sample, kg

N

number of pulses

n

liquid to solid ratio

S

solid volume, m³

t

time, min

t_PEF

PEF treatment duration, s

U

current tension, V

W

specific energy consumption during the PEF treatment, kJ/kg

τ

duration of pulse, s

Article Outline

Nomenclature

1. Introduction

2. Materials and methods

3. Results and discussion

3.1. Reproducibility of results

3.2. Effect of pulsed electric field parameters

3.3. Effect of stirring

3.4. Effect of sample type

4. Conclusion

References