filtration of grape juice sediments: a new application … of grape juice...filtration of grape...

28 www.wineb i z .com.au Wine & Viticulture Journal MARCH/APRIL 2012 V27N2

W I n e M A K I n g f I L t R A t I o n

IntRoDuCtIon

Grape juice for white wine is usually pre-clarified to a certain degree before undergoing

alcoholic fermentation. Traditionally, this pre-clarification has been done by allowing particles to settle overnight and racking off the clear juice. The settled particles (sediments) are filtered with a filter press or a rotary vacuum filter to obtain higher yields of clear juice. These techniques have proved to be efficient, but contain inconveniences, such as the removal of filtration residues (including adjuvants like diatomaceous earth, perlite, etc.) which may pose environmental concerns (Montigaud 2010, Desenne 2004). Other important concerns in wineries are the initial dilution of the juice, little filter versatility, and labour hours for the cleaning procedure. Rotary vacuum filters have been studied extensively over the last 40 years. Some of the main consequences found for the filtered juices are linked to the use of the vacuum itself: decrease of carbon dioxide concentration and free sulfur dioxide levels, losses of some desired volatile compounds (e.g., primary aromas), and increased risk for juice oxidation (Riberau-Gayon et al. 1998).

The first cross-flow filters used in the wine industry were reported to have heavy impacts on the filtered wines. Such wines reached lower scores than wines made from rotary vacuum-filtered juices, as evaluated by professional tasting panels (Serrano and Paezold 1998). In recent studies with updated filter technology and improved membrane characteristics, no differences were found between wines from cross-flow filtered and rotary vacuum-filtered juices (Etienne and Benestau 2000, Cuénat et al. 2003). However, Vernhet et al. (1998) analysed wine components in the laboratory and reported lower levels of colloidal compounds in wines from cross-flow filtered juices compared with wines from rotary vacuum-filtered juices. Cuénat et al. (2003) noted in a study that ceramic

membranes retained more colloids than membranes made with polysulfone.

Cross-flow filters with adapted modules for the filtration of dense sediments appeared on the market only recently. This new application for cross-flow filters offers the possibility to filter wines, juices, and juice sediments with one device. The present study was carried out as part of a Bachelor of Sciences thesis (De Giorgi 2010) at the School of Enology in Changins, Switzerland, to evaluate the impact of this new application on the quality and composition of the final wines. Cross-flow filtration of juice sediments was compared with the standard filtration with a rotary vacuum filter.

MAteRIALs AnD MetHoDs

Two experiments were carried out with two pre-clarification methods (gravitational settling and flotation). After pre-clarification, sediments were filtered with a rotary vacuum filter and compared with the filtration from a cross-flow filter.

Filter technologyA cross-flow filter FX 3 (Bucher

Vaslin SA, France) was equipped with an adapted module and the corresponding computer software, which allows the filtration of very dense and viscous juice sediments. The membrane was made of polyether

Filtration of grape juice sediments: a new application for cross-flow filtersBy Patrik Schonenberger1, Davide De Giorgi1 and Julien Ducruet1,2 1Engineering School of Enology in Changins, Route de Duillier 50, Case postale 1148, 1260 NYON 1, Switzerland 2Corresponding author: Dr Julien Ducruet. Email: [email protected]

figure 1. Cross-flow filter fx 3 (bucher-Vaslin sA, france), equipped with an adapted module and the corresponding computer software, which allows the filtration of very dense and viscous juice sediments.

V27N2 Wine & Viticulture Journal MARCH/APRIL 2012 www.wineb i z .com.au 29

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sulfone with ‘spaghetti’-type capillaries (internal capillary diameter 3mm). The filtration surface was 18m2 with 0.2µm pore size. Water (cold and hot) and compressed air were connected permanently for proper running of the filter. The computer software controlled all valve openings (wine, water and air) and supervised filtration, rinsing, and cleaning programming (Figure 1).

A rotary vacuum filter (VELO, Italy) with an integrated vacuum pump and a filtration surface of 8m2 was used as the standard procedure. Filtration media was Seitz® Perlite A (Pall SeitzSchenk Filter Systems GmbH, Germany).

Grape juiceWhite Chasselas (Vitis vinifera L. cv

Chasselas) juice from a commercial vineyard (Château d’Auvernier, Switzerland) was used. Enzymes (10mg/L Depectil Clarification FCE®, Martin Vialatte) and SO2 (80mg/L) were added to the juice before the application of the treatments. The fraction of the juice that was floated before filtration received 200mg/L gelatin (proVgreen Extra®, Martin Vialatte) prior to flotation, in addition to the enzymes and

the SO2. No other product was added to the juice. One fraction of the juice was pre-clarified overnight by gravitational settling at ambient temperature (16°C). A second fraction was pre-clarified by flotation, using a Turboflot ECO 5000 (Kunzmann and Hartmann, Germany) with an average flow rate of 7500L/h. Flotation gas was nitrogen. The sediments of both pre-clarification methods were then filtered using both cross-flow and rotary vacuum filtration. Inherent to rotary vacuum filtration, the first fraction of the juice was diluted and not used for the winemaking.

WinemakingSpecial care was taken to use only

juice fractions with the same sugar levels (total soluble solids) before and after filtration. After filtration, wines were replicated three times in stainless steel tanks (each containing 200L of juice). Standard procedures for white Chasselas wine production in Switzerland were applied, and attempts were made to keep the temperatures identical in all tanks, i.e., alcoholic fermentation at 18°C and malolactic fermentation at 16°C. For the alcoholic fermentation, all tanks were inoculated

separately with 0.2g/L Vitilevure Quartz (Saccharomyces cerevisiae galactose, Station Oenotechnique de Champagne, France). For the malolactic fermentation, 0.01g/L Vitilactic F (Martin Vialatte, France) was added to the wines. SO2 at a rate of 50mg/L was added after malolactic fermentation, and the wines were then stored at 2°C for a period of six weeks for physical stabilisation. Wines were pre-filtered with AF100 filter pads (Filtrox AG, Switzerland) and, before bottling, were sterile filtered with AF130 filter pads (Filtrox AG, Switzerland).

Chemical analysisThe sugar content of the juice

was measured with a standard refractometer. Alcohol content, titratable acidity, tartaric acid, malic acid, lactic acid, and volatile acidity were analysed with a WineScanTM (FOSS Analytical, Hilleroed, Denmark) which uses Fourier Transform Infrared (FTIR) Spectroscopy. The FTIR analysis was carried out with the clear fraction of the juice after centrifuging the samples for 10 minutes at 5000rpm. Samples were also centrifuged for calculating the proportion of dry matter in the total



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volume. The volume of the centrifuge deposit was divided by the initial total volume to obtain the percentage of dry matter.

Statistical analysisData were subjected to the analysis

of variance (ANOVA) and F-test. The co-efficient of variation (CV) was calculated to obtain the relative percentage of the standard deviation (Excel 2007, Microsoft, Redmond, WA).

Sensory evaluationThe bottled wines were stored for

three months before being exposed to sensory evaluation by an expert panel. Two panels of 24 and 16 judges, respectively, were present at two tasting sessions. Quantitative Descriptor Analysis profile (QDA®) with 10 different terms was employed to describe the wines.

ResuLts AnD DIsCussIon

Chemical analyses of the initial juices are shown in Table 1 (total soluble solids, titratable acidity, pH, and dry matter as a percentage of the total volume). The two types of sediments obtained by flotation and gravitational settling were distinctly different: sediments from flotation were denser and more viscous than sediments from gravitational settling (28.25% versus 8.78% dry matter of total volume, Table 1). Both filtration techniques cleared the juice to a very low but comparable level of suspended material (<1.00% dry matter of total volume, data not shown). A temperature rise of 6°C was observed in the juice during cross-flow filtration (data not shown) and needs some consideration. Similar differences for input and output temperatures for cross-flow filtered wines have been

reported previously in comparative studies (Ducruet et al. 2006). Cross-flow filtration may negatively affect a juice with a higher input temperature. It is preferable to conduct the filtration with an initial juice temperature below 16°C to reach a maximum temperature of 22°C at the output side of the filter.

The chemical analyses of the finished wines showed no significant differences for alcohol content, acidity levels, and volatile acidity (Tables 2 and 3).

Significantly lower absorbance at 280nm was observed in wines made from rotary vacuum-filtered juices compared with those from cross-flow filtered juices (Tables 2 and 3). The absorbance at 280nm is an indication for total polyphenols in the juice. If rotary vacuum filtration caused more polyphenol oxidation than cross-flow filtration (Riberau-Gayon et al. 1998), one portion of these oxidised

Juice analysis total soluble solids (brix) titratable acidity (g/L) pH Dry matter (% of total volume)

After gravitational settling 19.1 7.10 3.29 8.78

After flotation 19.1 7.30 3.22 28.25

table 1. Chemical analyses of the initial juice after pre-clarification by gravitational settling and flotation.



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Wine analysis

Alcohol (% volume)

tartatic acid (g/L)

Malic acid (g/L)

Lactic acid (g/L)

Acetic acid (g/L)

Volatile acidity (g/L) Absorbance (280 nm) Chromtic intensity

(absorbance 420 nm)

Juice obtained by gravitational settling

Rotary vacuum filter

10.9 1.73 0.41 1.94 0.23 0.42 5.267 0.143

Cross-flow filter 11.1 1.70 0.47 2.25 0.18 0.42 6.000 0.154

significance ns ns ns ns ns ns ** ns

CV % 3.05 3.62 4.45 3.77 21.25 3.09 2.33 19.24

table 2. Chemical analyses of the final wines made from juice obtained by gravitational settling. Juice was filtered, vinified, stabilised, and stored for three months in the bottle.

Wine analysis

Alcohol (% volume)

tartaric acid (g/L)

Malic acid (g/L)

Lactic acid (g/L)

Acetic acid (g/L)

Volatile acidity (g/L) Absorbance (280 nm) Chromatic intensity

(absorbance 420 nm)

Juice obtained by flotation

Rotary vacuum filter

11.3 1.67 0.48 2.05 0.28 0.47 5.650 0.223

Cross-flow filter 11.2 1.65 0.51 2.18 0.13 0.43 6.310 0.126

significance ns ns ns ns ** ns * *

CV % 0.04 0.04 0.22 4.73 18.62 8.51 7.52 45.77

table 3. Chemical analyses of the final wines made from juice obtained by flotation. Juice was filtered, vinified, stabilised, and stored for three months in the bottle.

*, **, ***, ns: Main effects significant at P < 0.05, P < 0.01, P < 0.001, or not significant, respectively.

*, **, ***, ns: Main effects significant at P < 0.05, P < 0.01, P < 0.001, or not significant, respectively.



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polyphenols might have flocculated and immediately filtered out of the juice, which did lower total polyphenols in rotary vacuum-filtered juices. The portion of the remaining oxidised polyphenols (indicated by chromatic intensity) was not different in both filtration techniques, if the juice was

obtained by gravitational settling (Table 2). On the other hand, if the juice was obtained by flotation, the portion of the oxidised polyphenols (indicated by chromatic intensity) and acetic acids were increased in rotary vacuum-filtered juices (Table 3). However, a high CV of 18.62% and 33.3%, respectively,

suggested that other factors than the application of the treatments may have influenced these data (Table 3).

The QDA profiles of the tasting panels showed few differences in the final wines (Figures 2 and 3). Cross-flow filtration of juice sediments produced wines with less intense odours and more pronounced acidity levels compared with wines from rotary vacuum-filtered juice sediments.

ConCLusIon

Cross-flow filters offer several possibilities to facilitate cellar work. They produce less filtration residues and may free labour hours through automation during intense harvest time. Cross-flow filters are more versatile than rotary vacuum filters; one filter may be used for wine, juice, and juice sediment filtration. However, initial investments are more substantial for a cross-flow filter. Some products (e.g., bentonite, activated charcoal) may not be added to the juice before cross-flow filtration, in order to prevent the membrane from plugging. These experiments were carried out with one grape variety and one vintage.

figure 2. Quantitative Descriptor Analysis profile (QDA®) of the final wines made with juice obtained by gravitational settling (*, **, ***: Main effects significant at P < 0.05, P < 0.01, P < 0.001).



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Further studies need to be done to better understand the behaviour of the juices and finished wines over time after using cross-flow filter technology.

ACKnoWLeDgeMents

The project was conducted as part of Davide De Georgi’s Bachelor of Science thesis, which was supervised by Dr Julien Ducruet. We greatly appreciated the technical assistance of M. Droz Frédérique (Château d’Auvernier, Switzerland) and M. Erik Dobrovolski (Bucher Vaslin SA, France).

RefeRenCes

Cuénat, P.; Lorenzini, F. and Bregy, C.A. (2003) Comparaison de membranes en céramique et polysulfone pour la microfiltration tangentielle des vins. Revue Suisse de Viticulture, Arboriculture, Horticulture 35(6):110-119.

DeGiorgi, D. (2010) Etude de la filtration tangentielle des bourbes comparée aux techniques existantes. BS Thesis, Engineering School of Enology in Changins, Switzerland.

Desenne, A. (2004) Les filtrations: une pollution différente selon le typ de filtre. Chambre d’agriculture de la Gironde service vigne et vin. http://www.matevi-france.com/welcome_menu.asp?tp=choix_experimentation [accessed 10/02/2010]

Ducruet, J.; Silvestri, A.-C. and Hyppenmeyer, P. (2006) Etude comparative de différents filtres

tangentiels en œnologie. Revue Suisse de Viticulture, Arboriculture, Horticulture 38(5):297-302.

Etienne, F. and Benestau, F. (2000) Filtration tangentielle: impact sur la qualité des vins. Revue des Œnologues 27(96):13-15.

Montigaud, I. (2010) Les terres de filtration pourraient finir en compost. Réussir Vigne. N°164: 35.

Riberau-Gayon, P.; Glories, Y.; Maujan, A. and Dubourdieu, D. (1998) La clarification des vins par filtration et centrifugation. Traité d’œnologie. Vol 2.

Chimie du vin stabilisation et traitements. Edition Dunod: 383-427.

Serrano, M. and Paetzold, M. (1998) Incidence des filtrations sur la composition chimique et les qualités organoleptiques des vins. Journal International des sciences de la vigne et du vin. Traitements physiques des moûts et des vins. Filtration. N° hors série. pp 53-57.

Vernet, A.; Moutounet, M. and Escudier, J-L. (1998) Microfiltration tangentielle des vins. Journal international des sciences de la vigne et du vin. Traitements physiques des moûts et des vins. Filtration. N° hors série 45-52.

figure 3. Quantitative Descriptor Analysis profile (QDA®) of the final wines made with juice obtained by flotation (*, **, ***: Main effects significant at P < 0.05, P < 0.01, P < 0.001).

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filtration of grape juice sediments: a new application … of grape juice...filtration of grape...

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