Deacidification of passion fruit juice by electrodialysis with bipolar membrane after different pretreatments

Journal of Food Engineering 90 (2009) 67–73

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Deacidification of passion fruit juice by electrodialysis with bipolar membrane after different pretreatments Edwin Vera a, Jacqueline Sandeaux b, Françoise Persin c, Gérald Pourcelly b, Manuel Dornier d,*, Jenny Ruales a a

Department of Food Science and Biotechnology, Escuela Politécnica Nacional, P.O. Box 17012759, Quito, Ecuador Institut Européen des Membranes, Université de Montpellier II, CC 047, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France c UMR 016, Université de Montpellier II, CC 005, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France d UMR Qualisud, CIRAD – Montpellier SupAgro, 73 rue Jean-François Breton, TA B-95/16, 34398 Montpellier Cedex 5, France b

a r t i c l e

i n f o

Article history: Received 5 October 2007 Received in revised form 17 March 2008 Accepted 3 June 2008 Available online 11 June 2008 Keywords: Passion fruit juice Deacidification Bipolar electrodialysis Pulpy juice Clarified juice Centrifuged juice

a b s t r a c t The reduction of acidity of passion fruit juice was investigated by electrodialysis (ED) with bipolar membranes (BM) at the laboratory and pre-industrial scale. Four states of juice were tested: initial pulpy juice, juice clarified by tangential microfiltration, twice-concentrated clarified juice, centrifuged juice. The ED performances were compared in terms of deacidification rate, current efficiency, and energy consumption. The deacidification was carried out up to pH 4.5 with satisfactory results. ED performances were lower with the pulpy and concentrated juices because of fouling of the anion-exchange membrane, which increased voltage. The differences in acidity between the juices was reduced by the pre-industrial ED stack, which involved better hydrodynamics through high flow rates and low compartment thickness. Whatever the juices, physico-chemical analysis showed that colour changed only slightly. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Tropical fruit juices are appreciated for their intense aroma and flavour. Yet, their quality could be improved by reducing their acidity. Electrodialysis (ED) is an interesting method for deacidification of passion fruit juice, relative to calcium salt precipitation, which involves addition of chemical reagents, and relative to ion-exchange resins, which strongly modify the aroma and provide effluents during the regeneration step (Vera et al., 2003a, b). ED has shown satisfactory performances for deacidification of various fruit juices such as orange (Goboulev and Salem, 1989), grape, pineapple (Adhikary et al., 1983), castilla mulberry, naranjilla, and araza (Vera et al., 2007b). Moreover, the sensorial characteristics of fruit juices were only slightly modified (Vera et al., 2007a). The use of bipolar membranes (BM) for the deacidification has additional advantages, since the electrohydrolysis of water produced in the BP membrane (Kemperman, 2000) allows to produce H+ and OH ions, which can be used for the deacidification, and the production of organic acids (Bailly, 2002), leading to an economical and environmental benefits (Chuanhui and Tongwen, 2006; Chuanhui et al., 2007).

Membrane fouling was the main limiting factor of the process, but it could be reduced by modifying current density and flow rate specifically for each juice (Vera et al., 2007b). In the previous works, ED was done on clarified juices. The aim of the present study is to investigate the feasibility of ED treatment of a fruit juice without and with various pretreatments, in order to explore the best way to process a fruit juice by ED, and to evaluate the variation of performances and fouling of membranes. The juice studied was that of passion fruit, at the initial state and after pretreatments such as clarification by tangential microfiltration and centrifugation. These pretreatments was chosen since, as shown in Fig. 1, if the target is to obtain a pulpy deacidified juice, it can be done by direct deacidification of the initial pulpy juice, by mixing slurry and deacidified centrifuged juice, or by mixing retentate and deacidified permeate when microfiltration was used for clarification. The simplest way is to deacidify the pulpy juice, but increased fouling problems could appear. Moreover, the ED deacidification of a concentrated clarified juice was investigated because the fruit juices are often marketed as a concentrate. 2. Materials and methods 2.1. Passion fruit juice

* Corresponding author. Tel.: +33 467614432; fax: +33 467614433. E-mail address: [email protected] (M. Dornier). 0260-8774/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2008.06.003

Passion fruit juice (Passiflora edulis v. flavicarpa, Degener) was supplied by Tropifrutas, obtained as described in Vera et al.

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Nomenclature A AEM BM C C1 CP EC ED EDBM2C F H3Cit Rf

membrane area (m2) anion-exchange membrane bipolar membrane concentration (mol dm3) electrodialysis compartment juice compartment electrode compartment electrodialysis bipolar electrodialysis with two compartments Faraday’s constant (96,500 C mol1) citric acid current efficiency (dimensionless)

i j J

j n t TA TDS TS U V W

current intensity (A) current density (A m2) deacidification rate (mol h1 m2) conductivity (mS cm1) number of unitary cells (dimensionless) time (s) titrable acidity (g kg1) total dissolved solids (g kg1) total solids (g kg1) voltage (V) volume (dm3) energy consumption (kWh mol1)

(2003b). The main characteristics of the initial passion fruit juice are given in Table 1. The pH was close to three, and the acidity was mainly due to citric acid. Citrate and potassium ions were the most abundant anions (91%) and cations (94%), respectively. Total minerals represented 8.3 g kg1. This fruit juice had a viscosity of 2.0 mPa s at 30 °C and a conductivity of 6.4 mS cm1 at 25 °C. These data are similar to those in the literature (Espiard, 2002; INNE, 1965; Serna and Chacon, 1988).

2.4. Concentration

2.2. Clarification

Table 1 Main characteristics of the initial pulpy passion fruit juice, retentate and permeate after crossflow micro-filtration

The clarification was achieved by using crossflow microfiltration. The filtration unit consisted of a ceramic membrane (Membralox 1P1940 PL, Exekia) of 0.2 lm average pore diameter and 0.2 m2 effective area. The operating conditions were pressure 2.5 bar, temperature 35 °C, and crossflow velocity 5 m s1 (Villarreal, 1999). Before clarification, the juice was treated with the Pomaliq enzyme from Gist-Brocades (France) to partially hydrolyze the polysaccharides and was gently filtered (Vaillant et al., 1999). The treatment consisted in adding 1 cm3 of the enzymatic solution in 1000 cm3 of juice during 30 min at 30 °C. 2.3. Centrifugation Centrifugation was used as an alternative method to separate the pulp from the juice. The initial pulpy juice was centrifuged at 2000g/10 min (Beckman Coulter Allegra 21, rotor S4180).

After clarification, some samples of juice were concentrated with an evaporator under vacuum (Centrithem CT-IB-2, Alfa Laval) and the following operating conditions: – evaporation room: 0.16 bar, 55 °C, – heating steam: 0.86 bar, 95 °C.

Pulpy juice

Retentate

Permeate

pH

2.97 ± 0.05

2.98 ± 0.05

2.95 ± 0.05

Coloura: L a b

36.84 ± 0.63 0.51 ± 0.11 24.24 ± 0.76

54.61 ± 2.32 8.59 ± 1.08 67.80 ± 2.51

31.77 ± 0.11 1.04 ± 0.04 6.58 ± 0.40

TS (g kg-1) TDS (g kg-1)

145 ± 1 135 ± 3

149 ± 2 135 ± 3

– 135 ± 3

Total sugars (g kg1) Fructose Glucose Saccharose

72.1 ± 2.4 25.2 ± 1.3 28.9 ± 2.0 17.9 ± 2.4

73.5 ± 2.0 not determined not determined not determined

71.7 ± 1.8 26.0 ± 1.8 28.4 ± 1.2 17.3 ± 1.0

Titrable acidity (g kg1) Citric acid Malic acid

42.8 ± 1.4 54.1 ± 3.8 3.3 ± 0.2

45.4 ± 0.3 52.7 ± 6.1 4.3 ± 0.5

44.8 ± 0.8 57.4 ± 3.6 3.6 ± 0.2

x ± standard deviation; replications = 2. a Measured using the CIELAB colour space.

Fig. 1. Production of a deacidified pulpy juice by various ways.

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E. Vera et al. / Journal of Food Engineering 90 (2009) 67–73

2.5. ED equipment and operating conditions

Table 2 Characteristics of the electrodialysis cells and operating conditions

Among two ED configurations tested in the previous works (Vera et al., 2007b), only ED with bipolar membranes and two compartments (EDBM2C configuration) was used in this study. Citric acid (H3Cit) is mainly responsible for the high acidity of passion fruit juice. Thus, the deacidification principle consisted of a partial extraction of citrate anions from the juice and partial neutralization of protons by hydroxyl ions provided by a bipolar membrane in contact with the juice. Moreover, this ED configuration allowed the production of citric acid in the C1 adjacent compartment of juice by combining the extracted citrate anions with protons provided by a second bipolar membrane separating the C1 and electrode compartments (EC). Four states of passion fruit juice were treated: – initial pulpy juice without pretreatment, – juice clarified by tangential microfiltration at the initial concentration, – twice-concentrated clarified juice, – centrifuged juice at the initial concentration. Electrodialysis experiments were performed using a lab-cell (PL20) and a pre-industrial pilot (P-200), each with a similar stack design (EDBM2C) as depicted in Fig. 2. The unit cell was equipped with one anion-exchange membrane (AEM) (Neosepta AXE01, Tokuyama) and two bipolar membranes (BM) (Neosepta BP-1, Tokuyama) constituting two compartments (C1 and juice) besides the electrode compartments (EC). The four kinds of juice have been tested, but the concentrated clarified juice was not treated in the P-200 pilot, while the centrifuged juice was not treated in the PL-20 cell. The characteristics of the ED pilots and the operating conditions are in Table 2. The main differences between the pilots used are the following: unit membrane area 10 times greater, number of unit cells 7 times greater, and compartment spacing 13 times lower for the pre-industrial pilot than for the lab-cell. The current density and flow rate were chosen from previous works showing that no fouling appeared during treatment of clarified passion fruit juice Vera et al., 2007b. ED operations were carried out in batch mode, at 25 °C. Voltage, conductivity, and pH were monitored during all the experiments, which were performed until pH 3.3–4.6 was reached in the juice in the PL-20 cell, and until pH 4.5–4.6 in the P-200 pilot. 2.6. Analytical methods Total dissolve solids (TDS) was measured by refractometry with an Atago hand refractometer. Total solids (TS) were determined by drying in an oven under vacuum at 70 °C for 15 h (AOAC, 2000). Suspended solids were assayed by centrifuging at 3300g for 15 min, draining the supernatant for 5 min and weighting the settled solids (Vaillant et al., 2001). Titrable acidity (TA) was deter-

BM EC

AEM C1

-

BM JUICE

+

EC

+

X ,H

OH

+

+

H

-

-

H2Cit , A

+

Na

+

Na

SO4

=

SO4

-

=

-

OH

PL-20

P-200

Membrane area (cm ) Number of unitary cells Width of compartments (cm) Height of compartments (cm)

20 1 4 5

200 7 11.3 17.7

Thickness of compartments (cm) Juice, C1 EC

0.8 0.8

0.08 0.98

Spacers

no

yes

Volume of solutions (dm3) Juice C1 EC

0.2 1 1

1.8 4 3

Flow rate (dm3 h1) Linear speed (cm s1) Current density (A m2)

10.8 0.7 200

150 45 200

2

mined by titration with 0.1 mol dm3 NaOH (AOAC, 2000). Colour was assayed with a Minolta CR-A70 colorimeter in the CIELAB space, and the colour variation was calculated according to Vera et al. (2007b). Sugars were analysed in by HPLC with acetonitrile: water 70:30 as mobile phase, an Astec NH2 Purospher column and an IR detector. 3. Results 3.1. Clarification by tangential micro-filtration Table 1 shows that all parameters remained unchanged in the retentate and permeate, except the colour. The measurement of colour by L, a, b method is based on spectral distribution of the light reflected by the sample. This reflection can be modified by suspended solids, which were eliminated in the permeate. Nevertheless, note that no retention of sugars and organic acids was induced by the microfiltration membrane. These results are in accordance with previous works (Vaillant et al., 1999). 3.2. Concentration of clarified juice The clarified juice was concentrated until a TDS value of 600 g kg1 was obtained, and then various dilutions were carried out to analyze the change in physico-chemical properties as a function of the TDS amount. Results are shown in Fig. 3. Conductivity showed a maximum at about 300 g kg1 TDS. At low TDS values, the increase in conductivity was due to an increase in the concentration of ionic compounds. After the maximum value, the decrease in conductivity was related to a high increase in viscosity, as can be seen in the plot of viscosity vs. TDS. Indeed, the Walden product (Lobo, 1989; Robinson and Stokes, 1959), K  l, with K the molar conductivity and l the viscosity, must be constant for electrolyte solutions, and it explains the behaviour of conductivity with the increase of viscosity. The acidity increased linearly with the concentration of TDS, which means no modification of organic acids occurred during the concentration step. Despite the significant increase in acidity, a slight pH decline was observed because the weak acids acted as a buffer. From all these results, a TDS concentration of 270 g kg1 was retained for ED experiments.

+

H

3.3. ED deacidification

Fig. 2. Configuration of the EDBM2C cell. The two EC compartments are connected.

The Table 3 shows some properties of the juices employed for the ED tests. The pH, TDS and titrable acidity were very similar

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Conductivity

12

Viscosity 50

k (mS.cm-¹)

10

40

µ (mPa.s)

8 6 4

30 20 10

2 0

0 0

200

400

600

0

200

TDS (g.kg-¹) Titrable acidity

250

400

600

TDS (g.kg-¹) pH 4

3

150

pH

TA (g.kg-¹)

200

100 2 50 0

1 0

200

400

600

0

200

TDS (g.kg-¹)

400

600

TDS (g.kg-¹)

Fig. 3. Evolution of conductivity, viscosity, titrable acidity and pH of the clarified passion fruit juice at different strengths.

Table 3 Main characteristics of the fruit juices treated by electrodialysis Pulpy juice Centrifugated Clarified pH 2.97 ± 0.05 TS (g kg1) 145 ± 1 TDS (g kg1) 135 ± 3 1 Suspended solids (g kg ) 107 Viscosity (mPa s) 2.40 Titrable acidity (g kg1) 44.6 ± 1.4 Conductivity (mS cm1) 6.40

2.96 ± 0.05 141 ± 2 134 ± 3 0 1.70 43.0 ± 0.3 6.90

Concentrated

2.95 ± 0.05 2.88 ± 0.05 – – 135 ± 3 270 ± 3 0 0 1.13 2.31 44.8 ± 0.8 88.4 ± 0.3 8.05 10.20

x ± standard deviation. Replications = 2.

for the pulpy, centrifugated and clarified juices; the principal differences were on the TS, suspended solids, viscosity and conductivity. The concentrated juice had completely different properties because of the concentration process. Theoretically, the juices having lower viscosities and suspended solids, as well as higher conductivities will help ED treatment (Scott, 1995). 3.3.1. Voltage and pH variation The course of voltage and pH is plotted in Figs. 4 and 5 as a function of ED time. In both ED cells (PL-20 and P-200), the pH curves exhibit similar shapes whatever the state of treated juices, with the exception of the concentrated juice (Fig. 4), which shows lower pH

30

4.0

25

3.6

pH

Voltage (V)

3.8

20

3.4 3.2 3.0 2.8

15 0

150

300

450

0

600

150

Time(min) × Pulpy

300

450

600

Time(min) Clarified

Concentrated

Fig. 4. Evolution of voltage and pH of the passion fruit juice in the ED deacidification with the PL-20 pilot.

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60

4.8

55

pH

Voltage (V)

4.4 4.0 3.6 50 3.2 2.8

45 0

20

40

60

0

80

Time (min) × Pulpy

20

40

60

80

Time (min) Clarified

Centrifugated

Fig. 5. Evolution of voltage and pH of the passion fruit juice in the ED deacidification with the P-200 pilot.

values because the initial acidity increased due to the concentration effect, as depicted in Fig. 3. According to Grebenyuk et al. (1998), the fouling induces an increase in the electrical resistance of the membranes, leading to an increase in the applied voltage in the ED cell. Voltage remained constant (Fig. 4) or decrease (Fig. 5) for the clarified and centrifuged juices. On the other hand, Fig. 4 shows voltage was slightly higher for the pulpy juice and regularly increased during the treatment of the concentrated juice. Besides, Fig. 5 shows the voltage values were close at the beginning of the ED operation and that they increased after 40 min of treatment of the pulpy juice; this increment on voltage was not observed in the PL-20 cell, perhaps because the deacidification was stopped earlier (pH 3.3). The ED duration with the lab-cell was varied because of this behaviour. The increase in voltage was attributed to fouling when treating pulpy or concentrated juices, possibly due to the presence of insoluble solids in the case of the pulpy juice, and to the higher concentration of organic compounds in the case of the concentrated juice. Previous works with clarified passion fruit juice have shown that fouling occurred within the AEM, separating the juice and C1 compartments. Fouling depended on the operating conditions, such as current density and flow rate. It was not due to sugars but maybe to coloured compounds, mainly carotenoids in passion fruit juice. Nevertheless, fouling was lower than for other fruit juices such as castilla mulberry, which contains phenolic compounds like anthocyanidins that induce precipitation with a pH increase (Vera et al., 2007b). Consequently and as expected, fouling was increased by treatment of pulpy juice and even clarified juice if it was twice concentrated. This is probably caused by fouling of the membranes, since the conductivity of all the solutions were almost constant during the ED treatment (around 16.9 mS cm1 in the electrodes compartment, 4.7 mS cm1 in the C1 compartment and 6.4, 8.15 and 10.8 mS cm1 for the pulpy, clarified and concentrated fruit juices, respectively). The pretreatments which gave the best results were the centrifugation and clarification by MFT, however, the additional costs of these pretreatments must also be considered for an industrial application. 3.3.2. Physico-chemical analysis Table 4 shows the main physico-chemical properties of passion fruit juice before and after deacidification. No difference was found in the properties of the juices treated in the PL-20 or P-200 cells. The decline in the acidity and total dissolved solids depended on the final pH of deacidification. Previous works have shown that the decline in TDS was due to the variation of the organic acid and

Table 4 Main characteristics of the passion fruit juice before and after ED deacidification Juice Pulpy Initial Final

Clarified Initial Final

pH

TA

TDS

DE colour

2.93a 3.30a 4.00b 4.54b

44.6a 28.0a 11.5b 6.5b

135a 120a 112b 110b

0.66

2.90a 4.00a 4.50b

44.8a 12.2a 6.7b

135a 110a 108b

0.69

88.4a 34.6a

270a 246a

not determined

43.0b 8.8b 4.9b

134b 112b 110b

0.53

Clarified and concentrated Initial 2.88a Final 3.65a Centrifuged Initial Final a b

2.91b 4.04b 4.57b

Results obtained in the PL-20 cell. Results obtained in the P-200 pilot.

not to sugar concentration (Vera et al., 2007a). The results showed that similar properties were found for pulpy, centrifuged and clarified juices deacidified at same pH. Note that slight changes of colour were observed whatever the juices treated. Previous works (Vera et al., 2007a) have also shown that no changes of odour and flavour were detected for the passion fruit juice, compared to other treated fruit juices (castilla mulberry, naranjilla), because of its intense aroma. 3.3.3. Deacidification rate, current efficiency and energy consumption The performances of each ED operation were also compared in terms of deacidification rate, current efficiency, and energy consumption. Citric acid is a weak acid showing three successive dissociations. To quantify the current transport by citrate anions, it was considered that these ionic species bear an electric charge equal to one. Indeed, the distribution of ionic species showed that at the initial pH of juice (about 3), the citric acid was mainly under the molecular (H3Cit 56.9%) and monoionized (H2Cit 42.3%) forms, the (HCit2) form corresponding to only 0.7% (Vera, 2004). The pH variation during the ED, or local modifications of pH, can induce the formation of other ionic species, in fact at pH 4.5 there are mainly H2Cit (62.6%) and HCit2 (34.3%). Consequently, the electric charge of the ions transferred is unknown, and the assumption made permits simplify and compare the results of the different tests.

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The deacidification rate, J (mol h m2), defined as the extraction rate of citric acid, and the current efficiency, Rf (generally expressed in %), related to the transfer of the citrate anion from the juice to the C1 compartment under, were calculated as described in Vera et al. (2007a). The energy consumption, W (kWh/m3 juice), was calculated using Eq. (1).

P W¼

U D t  i  Dt V juice

ð1Þ

where UDt is the average voltage in the time interval Dt, measured when a constant current intensity, i, was applied to the cell. Results of these parameters are illustrated by Figs. 6–8.

Experiments performed with the lab-cell (Fig. 6) gave significantly lower performances for the pulpy and concentrated juices than those with the clarified one: the deacidification rate and current efficiency decreased while the energy consumption increased. In contrast, Fig. 7 exhibits a lower gap between the various states of juice treated in the pre-industrial pilot. One can deduce that fouling was reduced by the better hydrodynamics of the pre-industrial pilot, because of the low thickness of the compartments and high flow rate, 0.7 cm s1 in the PL-20 and 45 cm s1 in the P-200. Nevertheless, the ED performances were still slightly better for the centrifuged juice. Fig. 8 shows the comparison of the two ED pilots for the pulpy and clarified juices. By using the pre-industrial P-200 pilot, the deacidification rate and current efficiency increased about 13%

Deacidification rate

Current efficiency 40 30

2

Rf (%)

J (mol.h -¹.m -²)

3

1

20 10

0 pulpy

clarified

0

conc.

pulpy

clarified

conc.

Energy consumption

W (kWh / m³ juice)

500 400 300 200 100 0 pulpy

clarified

conc.

Fig. 6. ED performances of the PL-20 pilot for various states of the passion fruit juice at pH 4.

Deacidification rate

40

Current efficiency

30 2

Rf (%)

J (mol.h-¹.m -²)

3

1

20 10 0

0 pulpy

clarified

centrif.

W (kWh / m³ juice)

200

pulpy

clarified

centrif.

Energy consumption

150 100 50 0 pulpy pH 4.0

clarified

centrif. pH 4.5

Fig. 7. ED performances of the P-200 pilot for various states of the passion fruit juice.

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Deacidification rate

Current efficiency

40 30

2

Rf (%)

J(mol.h-¹.m-²)

3

1

20 10

0

0 clarified

W(kWh / m³ juice)

pulpy

500

pulpy

clarified

Energy consumption

400 300 200 100 0 pulpy P L-20

clarified P -200

Fig. 8. Comparison of the ED performances at pH 4 between the PL-20 and P-200 pilots for the pulpy and clarified passion fruit juice.

for the pulpy juice. An opposite variation was observed for the same parameters with the clarified juice. These results could be explained as follows: the decrease observed with the clarified juice could be related to the presence of spacers in the pre-industrial pilot that reduce the active area of membranes by about 9%. On the other hand, the increased deacidification rate and current efficiency with pulpy juice could be due to the better stack design of the P-200 pilot, that reduces membrane fouling more for pulpy than clarified juice; likely due to a reduction of the thickness of the fouling layer of the insoluble solids of pulpy juice. However, for both juices, the use of the P-200 pilot induced a significant decrease in energy consumption, by 70% and 60% for the pulpy and clarified juices, respectively. It is well known that industrial stacks, in comparison with lab-cells, improve ED performances because the low thickness of the compartments reduces the electrical resistance. That was in particular observed in the ED treatment of apple juice (Quoc et al., 2000). 4. Conclusion Many electrodialysis assays are achieved by using a lab-cell. Fouling is the main limiting factor of this membrane technique. Results obtained in this study showed that the use of a pre-industrial stack reduced fouling and allowed the deacidification of passion fruit juice even at the initial pulpy state. Nevertheless, the best ED performances were obtained with the clarified and centrifuged passion fruit juice. Thus, if the production of a pulpy deacidified juice is searched, the performance of the process could be improved by combining the ED technique with centrifugation (as showed in Fig. 1), instead of a direct deacidification of the pulpy juice, because of the high fouling observed during the ED of this kind of juice. References Adhikary, S.K., Harkare, W.P., Govindan, K.P., 1983. Deacidification of fruit juices by electrodialysis. Indian J. Technol. 21, 120–123. AOAC, 2000. Fruits and fruit products. In: Helrich, K. (Ed.), Official Methods of Analysis of Association of Official Analytical Chemists, vol. 2, seventeenth ed. Arlington, USA, pp. 37–38.

Bailly, M., 2002. Production of organic acids by bipolar electrodialysis: realizations and perspectives. Desalination 144, 157–162. Chuanhui, H., Tongwen, X., 2006. Electrodialysis with bipolar membranes for sustainable development. Environ. Sci. Technol. 40, 5233–5243. Chuanhui, H., Tongwen, X., Yaping, Z., Yanhong, X., Guangwen, C., 2007. Application of electrodialysis to the production of organic acids: state-of-the-art and recent developments. J. Membrane Sci. 288, 1–12. Espiard, E., 2002. Introduction à La Transformation Industrielle Des Fruits. Lavoiser, Paris. Grebenyuk, V.D., Chebotareva, R.D., Peters, S., Linkov, V., 1998. Surface modification of anion-exchange electrodialysis membranes to enhance anti-fouling characteristics. Desalination 115, 313–329. Goboulev, V.N., Salem, B., 1989. Traitement à l’électrodialyse du jus d’orange. Industries Alimentaires et agricoles 106, 175–177. INNE, 1965. Tabla de Composición de los Alimentos Ecuatorianos. Instituto Nacional de Nutrición, Ministerio de Previsión Social y Sanidad, Quito. Kemperman, A.J.B. (Ed.), 2000. Handbook of Bipolar Membrane Technology. Twente University Press, Enschede, Hollande, pp. 7–78. pp. 155–219. Lobo, V.M.M., 1989. Handbook of Electrolyte Solutions. Elsevier, New York. Quoc, A.L., Lamarche, F., Makhlouf, J., 2000. Acceleration of pH variation in cloudy apple juice using electrodialysis with bipolar membranes. J. Agric. Food Chem. 48, 2160–2166. Robinson, R.A., Stokes, R.H., 1959. Electrolyte solutions, second ed. Butterworths Publications, Londres, Angleterre. pp. 24–48, 223–252, 462–470. Scott, K., 1995. Handbook of industrial membranes. Elsevier Advanced Technology, Oxford, Angleterre. pp. 257–270. Serna, J., Chacon, C., 1988. El cultivo de maracuyá, third ed. Federation Nacional de Cafeteros de Colombia, Colombia Editolasers. ´ Brien, G., Dornier, M., Decloux, M., Reynes, M., 1999. Vaillant, F., Millan, P., O Crossflow microfiltration of passion fruit juice after partial enzymatic liquefaction. J. Food Eng. 42, 215–224. Vaillant, F., Millan, A., Dornier, M., Decloux, M., Reynes, M., 2001. Strategy for economical optimisation of the clarification of pulpy fruit juices using crossflow microfiltration. J. Food Eng. 48, 83–90. Vera, E., 2004. Désacidification de jus de fruits par électrodialyse. Doctorate Thesis of the University of Montpellier II, France. Vera, E., Ruales, J., Dornier, M., Sandeaux, J., Persin, F., Pourcelly, G., Vaillant, F., Reynes, M., 2003a. Comparison of different methods for deacidification of clarified passion fruit juice. J. Food Eng. 59, 361–367. Vera, E., Ruales, J., Dornier, M., Sandeaux, J., Sandeaux, R., Pourcelly, G., 2003b. Deacidification of the clarified passion fruit juice using different configurations of electrodialysis. J. Chem. Technol. Biotechnol. 78, 918–925. Vera, E., Sandeaux, J., Persin, F., Pourcelly, G., Dornier, M., Ruales, J., 2007a. Deacidification of clarified tropical fruit juices by electrodialysis. Part I. Influence of operating conditions on the process performances. J. Food Eng. 78, 1427–1438. Vera, E., Sandeaux, J., Persin, F., Pourcelly, G., Dornier, M., Piombo, G., Ruales, J., 2007b. Deacidification of clarified tropical fruit juices by electrodialysis. Part II. Characteristics of the deacidified juices. J. Food Eng. 78, 1439–1445. Villarreal, L., 1999. Estudio de las condiciones de operación para la clarificación de jugo de maracuyá mediante filtration tangencial. Report to obtain the Chemical Engineer degree, National Polytechnic Institute, Quito.