Separation and Purification by Ultrafiltration of White Wine High

Article pubs.acs.org/IECR

Separation and Purification by Ultrafiltration of White Wine High Molecular Weight Polysaccharides Ana Resende,† Sofia Catarino,‡ Vítor Geraldes,† and Maria de Pinho*,† †

ICEMS, Department of Chemical Engineering, Instituto Superior Técnico, Technical University of Lisbon, 1049-001 Lisbon, Portugal ‡ UEISTSA, Research Unity of Viticulture and Enology, Instituto Nacional de Investigaçaõ Agrária e Veterinária, I.P., 2565-191 Dois Portos, Portugal ABSTRACT: This work aims to develop a process of ultrafiltration in diafiltration mode to concentrate the fraction of white wine polysaccharides of high molecular weight (arabinogalactan-proteins and mannoproteins) and to purify this fraction in terms of polyphenols, organic acids, and minerals removal. The membrane ETNA 10PP from AlfaLaval was characterized by an hydraulic permeability, Lp, of 105 L/(h·m2·bar) and a molecular weight cutoff, MWCO, of 17 kDa. A membrane surface area of 0.036 m2 was installed in a Lab-Unit M20 from Alva Laval. The permeation operating conditions, in total recirculation mode, were a temperature of 25 °C, pressures ranging from 0.5 to 5 bar, and an average velocity of 0.94 m/s. The ultrafiltration in concentration mode was run up to concentration factors of 4.25, and when diafiltration was introduced the concentration factors went up to 6.3. The permeate fluxes were maintained at an average value of 58 L/(h·m2).

1. INTRODUCTION The chemical composition of wine is very complex, containing inorganic compounds (mainly alkaline and alkaline earth metals in the form of minerals) and organic compounds (glycerol, acids, sugars, nitrogen compounds, polysaccharides, polyphenols, volatile compounds, and vitamins) dissolved and/or dispersed in an aqueous solution of ethanol. The abundance and diversity of polysaccharides influences the organoleptic properties of wines, directly in its “body” and indirectly through modulation of tannin astringency. These polysaccharides can be divided into several classes: mannoproteins, arabinogalactans, usually linked to proteins, socalled arabinogalactan-proteins (AGP), and rhamnogalacturonan I (RGI) and II (RGII). The AGP 1,2 and the rhamnogalacturonan3,4 are released from the pectin of the cell walls of grapes, after degradation by pectinases. Arabinogalactan proteins represent about 40% of the wine polysaccharides,2 ranging between 100 and 200 mg/L in red wines and 50 and 150 mg/L in white wines.5 According to Gonçalves et al.6 mannoproteins can achieve 30% of the wine polysaccharides. The AGP and the mannoproteins constitute the fraction of polysaccharides with the highest molecular weight, in the range of 180−260 kDa and 53−560 kDa, for AGP and mannoproteins, respectively. Numerous studies have been conducted to identify the polysaccharides present in wines and some of its properties;2,4,7−11 namely, the mannoproteins12 are well-known as wine tartaric stabilizers due to its function as colloid protectors.6,13 Furthermore, gum arabic, also well-known by its excellent emulsifying properties, is a blend of natural polysaccharides composed of three fractions that vary in their molecular weight and protein: 90−99% arabinogalactan, 1−10% arabinogalactan protein, and 1% glycoprotein.14,15 In fact, these properties make © 2013 American Chemical Society

gum arabic very useful in several industries but especially in the food industry. However, its obtention for a wide range of applications in the food industry, due to its emulsifying properties and in particular as enological aid in tartaric stabilization and heavy metal complexation, is not yet well developed. The versatility of ultrafiltration in terms of the membranes covering a wide range of molecular weight cutoffs that overlap the range of molecular weight distribution of wine polysaccharides makes this operation particularly fitted to separate the high molecular weight fraction. Furthermore, ultrafiltration can be operated in diafiltration mode in order to purify the concentrated fraction. Therefore, the main objectives of the present work are (1) the optimization of ultrafiltration to separate and concentrate the high molecular weight fraction constituted by AGP and mannoproteins and (2) the optimization of ultrafiltration in diafiltration mode to minimize the content of polyphenols, organic acids, and minerals.

2. EXPERIMENTAL SECTION 2.1. Materials. Wine. Ultrafiltration/diafiltration experiments were carried out with a white wine, produced in the Instituto Nacional de Investigaçaõ Agrária e Veterinária (Dois Portos, Portugal) by conventional winemaking technologies. The summary analysis of the wine is presented in Table 1. The reducing sugars were quantified by segmented continuous flow after reaction with neocuproine (colorimetric method). The Special Issue: Giulio Sarti Festschrift Received: Revised: Accepted: Published: 8875

October 24, 2012 April 3, 2013 April 4, 2013 April 5, 2013 dx.doi.org/10.1021/ie3035493 | Ind. Eng. Chem. Res. 2013, 52, 8875−8879

Industrial & Engineering Chemistry Research

Article

0.94 m/s.18 The permeation experiments of white wine in concentration mode were performed at the transmembrane pressures of 1 and 2 bar. The volumetric concentration factor, VCF, is defined as the ratio of the initial volume to the final volume of wine in the feed tank. The VCF was varied from 1 up to 4.25. The permeation of white wine in UF/DF mode was performed at a transmembrane pressure of 1 bar. The volumetric concentration factor VCF* is now defined as the initial volume of the feed plus the accumulated volumes of DF water added divided by the final volume of wine in the feed tank. In all the permeation experiments the stabilization time for each run was 30 min. This corresponds to the time needed to achieve a stable concentration in the permeate. Membrane Cleaning. Membrane cleaning followed the permeation experiments, in total recirculation mode. This was performed with deionized water at 45 °C for at least two hours. In the case of that being ineffective (i.e., eight hours after washing) an alkaline cleaning with Ultrasil 10, 0.1% for 15 min at 45 °C, would take place. The fluxes were compared with those measured before the experimental runs and the cleaning efficiency was assessed. The cleaning efficiency was calculated as the ratio between the pure water flux after cleaning and the pure water flux of the clean membrane before the experiments. 2.3. Analytical Methods. The feed and permeate were analyzed in terms of salts, total polyphenols, and total polysaccharide contents. The determination of total polyphenols present in the samples was performed according to the colorimetric method of Folin-Ciocalteu. 19 The amount of polyphenols are determined by comparison with a calibration curve (gallic acid) using a spectrophotometer (Shimadzu UV, UV-1700). The total polysaccharide content was determined following the procedure described by Segarra et al.,20 the wine polysaccharides being precipitated with ethanol. The precipitate was dried and dissolved in water. The phenol−sulphuric method of Dubois et al.21 was used to analyze the total polysaccharide content. The amount of sugar present is calculated by comparison with a calibration curve (glucose).

Table 1. Physical and Chemical Composition of White Wine parameter

white wine

density (g/mL at 20 °C) Alcoholic strength (% v/v) total acidity (g/L tartaric acid) volatile acidity (g/L acetic acid) pH free sulfur dioxide (mg/L) total sulfur dioxide (mg/L) reducing sugars (g/L) color (420 nm) total polysaccharides (mg/L) total polyphenols (mg gallic acid/L)

0.9989 13.5 5.0 0.5 3.16 7 150 2.8 0.106 516 169

other enological parameters were determined according to the EU regulations (Reg. CEE n° 2676/90).16 Membranes. AlfaLaval composite fluoro polymer membranes, ETNA 10PP, were used. These membranes were characterized in terms of pure water hydraulic permeability (Lp) and molecular weight cutoff (MWCO). The Lp of 105 L/ (h·m2·bar) is the value of the slope of the linear variation of pure water flux vs the transmembrane pressure. The MWCO calculation is based on the results of permeation experiments of solutions of reference solutes (polyethylenoglycols of 4, 6, and 10 kDa) with a concentration of 300 mg/L. The MWCO of 17 kDa is obtained by the intersection of the curve of log( f/(1 − f)) vs the solute molecular weight with the 91% rejection line that corresponds to a value of log(f/(1 − f)) of 1. Here, f is the reference solute rejection coefficient defined as f = (Cb − Cp)/ Cb, where Cb and Cp are the feed and the permeate concentrations, respectively. The solute concentrations are determined through refractive index measurements. 2.2. Procedure. Permeation Experiments. Lab-Unit M20 represented in Figure 1 was used in the permeation

3. RESULTS AND DISCUSSION 3.1. Set Up of UF Operating Conditions. In order to study the influence of the transmembrane pressure on the permeation fluxes of UF of white wine, experiments in total recirculation mode were carried out at the maximum recirculation flow rate of 10 L/min that corresponds to an average velocity of 0.94 m/s. Figure 2 displays the variation of permeation fluxes with transmembrane pressure. For transmembrane pressures less than 1 bar there is a first linear increase of the permeation fluxes followed by a region of nonlinearity, and after transmembrane pressures of 2 bar the linearity is again achieved with a lower slope. A plateau or a limiting flux is not reached, and this result is very important as it indicates that white wine can be processed by UF over a wider range of pressures, without showing too many adverse effects of concentration polarization. The two linear asymptotic regions are Jp = 84.8ΔP and Jp = 22.2ΔP + 86.4 for low and higher pressures, respectively. The slope of the first linear variation of Jp vs ΔP is 84.8 L/ (h·m2·bar) and should be compared to the measured value of 105 L/(h·m2·bar) for the hydraulic permeability (Section 2.1).

Figure 1. Plate and frame DSS Lab-Unit M20.

experiments with the membrane ETNA 10PP with a surface area of 0.036 m2. The feed temperature was kept at 25 °C in all the experiments. All membranes were compacted through permeation experiments of pure water17 at a pressure of 5 bar and for a period of 3 h. This avoids pressure effects on membrane structure in the subsequent experiments. The permeation of reference solutions (polyethylenoglycols) for membrane characterization were performed at a transmembrane pressure of 0.5 bar and at a recirculation flow rate of 10 L/min that corresponds to an average tangential velocity of 8876

dx.doi.org/10.1021/ie3035493 | Ind. Eng. Chem. Res. 2013, 52, 8875−8879


Article

Figure 2. Variation of permeation flux of wine (JP) with transmembrane pressure (ΔP). Installation Lab-Unit M20: Membrane, ETNA 10PP; membrane surface area, 0.036 m2; temperature, 25 °C; recirculation flow rate, 10 L/min.

Figure 3. Variation of permeation flux of wine (JP) with volumetric concentration factor (VCF). Installation Lab-Unit M20: Membrane, ETNA 10PP; membrane surface area, 0.036 m2; pressure, 1 bar; temperature, 25 °C; recirculation flow rate, 10 L/min.

Figure 4. Variation of permeation flux of wine (JP) with volumetric concentration factor (VCF). Installation Lab-Unit M20: Membrane, ETNA 10PP; membrane surface area, 0.036 m2; pressure, 2 bar; temperature, 25 °C; recirculation flow rate, 10 L/min.

Although the fluxes of the permeation test at a pressure of 2 bar are higher, they decrease over the initial flux, 25%, more drastically than the ones of the permeation test at a pressure of 1 bar, 6%. The permeation fluxes decrease linearly with the increase of VCF up to values close to 2. From a VCF of 2.43 onward, the permeation fluxes are practically constant, and for tests performed at a pressure of 1 and 2 bar the fluxes are 73 L/ (h·m2) and 83 L/(h·m2), respectively.

The variation over the full pressure range, up to 4 bar, can be described by a single equation, Jp = [(84.8ΔP−5 + (22.2ΔP + 86.4)−5]−1/5, determined by a Churchill and Usagi algorithm.22 The evaluation of the permeation fluxes in concentration mode at the pressures of 1 and 2 bar is displayed in Figures 3 and 4, respectively. Each test started with 8.5 L of white wine and was carried out up to a final volume corresponding to a volumetric concentration factor (VCF) of 4.25. The VCF is the ratio of the initial volume by the final volume. 8877



Article

The variation of the permeate fluxes over the full range of VCF values displays a linear region for low values of VCF, a transition region up to a VCF of 2.43, and a linear constant value of 4.25. The experimental results over the full range of VCF are curve-fitted by a single equation (see Figures 3 and 4). These results led to the selection of 1 bar as the operating pressure in the subsequent UF/DF experiments. 3.2. Optimization of UF/DF. On the basis of the previous tests, the UF in DF mode was optimized to avoid a considerable decrease in permeation flux and allow the passage of compounds with molecular weight below the membranes MWCO, namely, polyphenols and polysaccharides of low molecular weight. A volume of 9 L of white wine was processed at a pressure of 1 bar, at a temperature of 25 °C and with the addition of 2 L of deionized water after 98 min, 227 min, 323 min, and 444 min and 1 L of water after 353 min and 414 min. The frequency of water addition was defined by setting 15% as the highest flux decline allowed. As shown in Figure 5, this resulted in the flux decline minimization and keeping it at approximately an average value of 58 L/(m2·h).

Figure 6. Gradation of color in permeate obtained (from 1 to 16 L) for UF/DF of wine. Installation Lab-Unit M20: Membrane, ETNA 10PP (MWCO 17 kDa); membrane surface area, 0.036 m2; pressure, 1 bar; temperature, 25 °C; recirculation flow rate, 10 L/min.

is displayed in Table 2. Increasing the VCF* up to 6.3 enables the reduction of the total polyphenols content from 175.3 mg/ Table 2. Concentration of Total Polyphenols (CPT) and Conductivity Present in UF/DF Concentratesa VCFb

CPT (mg gallic acid/L)

conductivity (μS/cm)

1.3 1.6 2.2 2.6 4.3 4.0 5.7 6.3

175.3 137.6 128.7 80.1 85.8 40.9 33.1 22.2

1714 1368 1530 1246 1264 772 632 380

a

Installation Lab-Unit M20: Membrane, ETNA 10PP (MWCO 17 kDa); membrane surface area, 0.036 m2; pressure, 1 bar; temperature, 25°C; recirculation flow rate: 10 L/min. bIn the definition of VCF to the initial volume of the feed, the accumulated volumes of DF water are added.

Figure 5. Wine diafiltration with membrane ETNA 10PP at a transmembrane pressure of 1 bar and 25 °C. Initial feed volume of 9 L.

The UF/DF operation was conducted with a UF membrane characterized by a molecular weight cutoff (MWCO) of 17 kDa in order to obtain in the concentrate stream the fraction of white wine high molecular weight polysaccharides. This fraction is well reported in the literature as being constituted by arabinogalactan-proteins (AGP) with molecular weights in the range of 180−260 kDa and mannoproteins in the range of 53− 560 kDa. For a white wine with a total polysaccharide content of 516 ± 9 mg/L, a final purified concentrate was obtained with a total polysaccharide content of 565 ± 8 mg/L. The diafiltration purification of this concentrate is associated with the removal of polyphenols, organic acids, and minerals. As seen in Figure 6, the three permeate samples of 5 L collected along the operation show a strong decrease of the color, revealing the passage of polyphenols to the permeate during the first time period of UF/DF. In the fourth permeate sample, with 1 L, this effect is still more pronounced. The analysis of the permeate samples gives evidence of the decrease of the polyphenols content along the UF/DF operation. In fact, they decrease from 167.39, 83.12, 41.44, and 20.1 mg gallic acid/L, at VCF* of 1.3, 2.6, 4.0, and 6.3, respectively. The decrease of the concentration of polyphenols and of the conductivity in the concentrate along the operation of UF/DF

L to 22.2 mg/L and the reduction of the conductivity from 1714 μS/cm to 380 μS/cm.

4. CONCLUSIONS Throughout this work a process of ultrafiltration was developed in diafiltration mode for the separation of purified fraction of high molecular weight polysaccharides. This polysaccharide fraction was concentrated from a value of 516 mg/L to a final value of 565 mg/L. The purification of the wine concentrate in terms of polyphenols removal means a depletion of polyphenols from an initial value of 169 mg/L to a final value of 22.2 mg/L. The process was operated at a low transmembrane pressure of 1 bar and still with a relatively high permeate flux of 58 L/(h·m2) that was almost constant in the range of VCF* from 1.3 to 6.3.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest. 8878



■

Article

(21) Dubois, M.; Gilles, K. A.; Hamilton, J. K.; Smith, F. Colorimetric method for determination of sugars and related substances. Anal. Chem. 1956, 28 (3), 350−356. (22) Churchill, S.; Usagi, R. A general expression for the correlation of rates of transfer and other phenomena. AIChE J. 1972, 18 (6), 1121−1128.

ACKNOWLEDGMENTS The authors would like to acknowledge Dr. Sara Canas (INIAV, I.P.) for helping with polyphenols analysis.

■

REFERENCES

(1) Saulnier, L.; Brillouet, J.-M.; Moutounet, M.; Hervé du Penhoat, C.; Michon, V. New investigations of the structure of grape arabinogalactan-protein. Carbohydr. Res. 1992, 224, 219−235. (2) Pellerin, P.; Vidal, S.; Williams, P.; Brillouet, J. Characterization of five type II arabinogalactan-protein complexes from red wine with increasing uronic acid content. Carbohydr. Res. 1995, 277, 135−143. (3) Doco, T.; Brillouet, J. Isolation and characterisation of a rhamnogalacturonan II from red wine. Carbohydr. Res. 1993, 243, 333−343. (4) Pellerin, P.; Doco, T.; Vidal, S.; Williams, P.; Brillouet, J.; O’Neill, M. Structural characterization of red wine rhamnogalacturonan II. Carbohydr. Res. 1996, 190, 183−197. (5) Doco, T.; Williams, P.; Moutounet, M.; Pellerin, P. Les polysaccharides du vin. Bull. de L’O.I.V. 2000, 73, 785−792. (6) Gonçalves, F.; Fernandes, C.; Cameira dos Santos, P.; De Pinho, M. N. Wine tartaric stabilization by electrodialysis and its assessment by the saturation temperature. J. Food Eng. 2003, 59, 229−235. (7) Vernhet, A.; Pellerin, P.; Prieur, C.; Osmianski, J.; Moutounet, M.. Charge properties of some grape and wine polysaccharide and polyphenolic fractions. Am. J. Enol. Vitic. 1996, 47, 25−30. (8) Doco, T.; Williams, P.; Vidal, S.; Pellerin, P. Rhamnogalacturonan II, a dominant polysaccharide in juices produced by enzymic liquefaction of fruits and vegetables. Carbohydr. Res. 1997, 297, 181−186. (9) Vidal, S.; Doco, T.; Moutounet, M.; Pellerin, P. Le rhamnogalacturonane II, un polysacharide complexe du vin aux propriétés remarquables. Rev. Franc. d’Oenol. 1999, 178, 12−17. (10) Vidal, S.; Williams, P.; O’Neill, M.; Pellerin, P. Polysaccharides from grape berry cell walls. Part I: tissue distribution and structural characterization of the pectic polysaccharides. Carbohydr. Polym. 2001, 45, 315−323. (11) Vidal, S.; Williams, P.; Doco, T.; Moutounet, M.; Pellerin, P. The polysaccharides of red wine: total fractionation and characterization. Carbohydr. Polym. 2003, 54, 439−447. (12) Gonçalves, F.; Heyraud, A.; De Pinho, M. N.; Rinaudo, M. Characterization of white wine mannoproteins. J. Agric. Food Chem. 2002, 50, 6097−6101. (13) Gonçalves, F.; Fernandes, C.; De Pinho, M. N. White wine clarification by micro/ultrafiltration: effect of removed colloids in tartaric stability. Sep. Purif. Technol. 2001, 22−23, 423−429. (14) Osman, M.; Menzies, A.; Martin, B.; Williams, P.; Phillips, G.; Baldwin, T. Characterisation of gum arabic fractions obtained by anion-exchange chromatography. Phytochemistry 1995, 38 (2), 409− 417. (15) Jayme, M.; Dunstan, D.; Gee, M. Zeta potentials of gum arabic stabilized oil in water emulsions. Food Hydrocolloids 1999, 13 (6), 459−465. (16) Commission Regulation (EEC) No 2676/90 of 17 September 1990. Official Journal of the European Communities. N. L272 of 3 October 1990. (17) Minhalma, M.; de Pinho, M. N. Development of nanofiltration/ steam stripping sequence for coke plant wastewater treatment. Desalination 2002, 149, 95−100. (18) Rosa, M. J. Separação Selectiva de Compostos Orgânicos de Correntes Aquosas por Ultrafiltração e Nanofiltração. Ph.D. Thesis, Instituto Superior Técnico, Technical University of Lisbon, Portugal, 1995. ́ (19) Curvelo-Garcia, A. Controlo de Qualidade de Vinhos. Quimica ́ Enológica; Métodos Analiticos; Instituto da Vinha e do Vinho: Lisboa, 1988. (20) Segarra, I.; Lao, C.; López-Tamames, E.; de la Torre-Boronat, M. Spectrophotometric methods for the analysis of polysaccharide levels in winemaking products. Am. J. Enol. Vitic. 1995, 46, 564−570. 8879


Separation and Purification by Ultrafiltration of White Wine High

Recommend Documents