Grape processing

The first step after the harvest is theremoval of the individual grapes from thegrape bunches. This happens with the helpof destemmers in which the harvest is putinto rotation by paddles rotating on a shaft(fingers) and is moved against the wall ofa perforated basket that turns around in thesame direction as the shaft. The grapes exitoutwards through the holes. The length ofthe destemmer zone, the basket (holediameter), the rpm and the number ofrotating fingers are varied according to thesize of the grapes and their sensitivity(variety and state of ripeness). For a newdestemming process without rackets, shaftand rotary basket, the Swiss enterpriseBucher Vaslin received the 2013 innova-tion award of INTERVITIS/INTERFRUC-TA in gold. The Delta Osxillys systemseparates the grapes from the combs in oneor two inclined baskets that perform aswinging pendulum motion. The force act-ing on the grapes in the process is greaterthan the stability of the connectionbetween grape and stalk. All componentsare separated from each other below thebasket on a roller sifter. The quality of thedestemming result by this system shouldbe about 5 to 10 times better than withconventional destemmers, i.e. the propor-tion of remaining green parts among thegrapes is about 0.2 to 0.5%, in contrast to2 to 4.5% conventionally.

The Selectiv‘ Process Winery system ofthe French manufacturer Pellenc hasalready been on the market a little longer,but it has now also received the innovationaward in gold. This compact machine isalso responsible for destemming and sort-ing. Also here, the destemming happens byhigh-frequency oscillations wherein thegrapes are pushed on a lattice tablebetween oscillating destemming modules

(see Figs. 1 and 2). The harvest then fallsonto the sorting table which consists oftwo parts. Fully toothed feed rollers sepa-rate the juice and small waste (seeds,stunted grapes, small insects...), align thestalks and prepare the harvest for sorting.The screen rollers with their studs let thesorted grapes fall through and they are col-lected in a trough beneath the sortingtable. The screen size is adjustable to thegrape size. About 95% of the leaf stalks >35 mm are discarded and the achievablecleanliness of the grapes is stated as99.8%.

Separation processes forclarification and sterilisation

For the clarification of wine and fruitjuice, the user basically has the choice

between decanters, separators, depth fil-ters and membrane filtration systems, andall systems were on exhibit with a greaterselection. The GEA Westfalia Groupexhibited the new GSC 110 ecoplus clari-fication separator for the middle and upperrange of performance. The hydrymachines of the ecoplus generation, withhydrostop, have a patented drum dischargesystem that should ensure maximum drymatter of the discharged solids and thuscorrespondingly low product losses for theclarification. The machines are made in ahygienic design and are provided with thepossibility of automatic CIP cleaning.With the specially designed hydrohermet-ic inlet and outlet system, gentle andfoam-free treatment of the product isachieved. Eaton demonstrated the new

22 F & S International Edition No. 14/2014

Highlights 2013

Separation technology in winemakingH. Lyko*

Wine is an ancient foodstuff and fundamental knowledge of cultivation and winery technology has a correspondinglylong tradition. Nevertheless, according to the opinion of experts, never before in history was there as much good wineas today, the organisers of INTERVITIS/INTERFRUCTA 2013 stated. On the way from the grape or the apple tree to thebottle, musts and wines go through a variety of treatment steps, among them a large proportion of mechanical separationprocesses. Besides classical criteria like hygienic design, handling, energy efficiency, ease of maintenance and throughput/yield, in the foreground for all processes there are always also the gentle treatment of the foodstuff and the extensivepreservation of all important flavours. At the Oenology congress accompanying the trade fair, the theme of Alcohol management was the focus. Climaticchanges and certain cultivation and vinification techniques sometimes led to excessive alcohol content in wine that canadversely affect the taste and regional typicity. The possibilities for adjusting alcohol content include viticultural measureslike cellar management measures. The latter are also summarised in the following contribution.

Fig. 1: Lattice table and destemmer modules of the Selectiv‘ Process Winery system, fromPellenc (image: Société Pellenc SA, France)

Fig. 2: Functionality of the Selectiv‘ Process Winery destemmer and sorting machine (image: Société Pellenc SA, France)

*Dr.-Ing. Hildegard LykoDortmund / Germany, Phone +49 (0) 231-730696

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depth filter candle BECO PROTECT CS CellStream, which com-bines the advantages of the innovative BECOPAD depth filtersheet material in one filter candle. With different features, costsavings and a saving of time should be achieved, as well as anincrease in productiveness. Thus, the nature of the winding causesa large filter area, the compact and backwashable design permits ahigher number of steam and regeneration cycles than with priormodels, as a result of which the service life is increased. The newdepth filter candle can be inserted with a standardised adaptor incustomary candle housings.

The new BECO LiquiControl2 index measuring instrumentfrom Eaton is used for the determination of wine  filterability. Indetail, a sample is filtered under defined, reproducible conditions(constant pressure) through a comparison membrane. Alternativelyto the membrane, the suitability of depth filter sheets can also bedetermined by connecting a laboratory monolayer filter. The sam-ple is considered to be filterable if a defined quantity of filtrate isobtained during the applied filtration pressure. Based on these testresults, the winemaker can decide whether further measures toimprove the filterability are necessary and coordinate the down-stream filtration process perfectly.

The BecoPad mentioned above is the first mineral-free depth fil-ter medium, which consists of specially treated high-purity cellu-lose. From this, according to the manufacturer, an especially lowcontent of ions and other flushable materials result.2BFermControl GmbH, Breisach, refers, inter alia, to the necessi-ty of minerals in its depth filter sheets with the trade nameViniFilter, made with brown diatomite and available in 5 separa-tion efficiencies. Therefore, mineral-free sheets allow valuableingredients to pass through almost without loss, have a problemat-ic pressure difference profile and tend to strike through towards theend of filtration. The question of which depth filter sheet is betteror worse can only be answered by a direct comparison. Such acomparison was made by employees of the Bavarian Landesanstaltfür Weinbau und Gartenbau (LWG), Veitshöchheim, with whitewines and red wines and published in February, 2013 in dasdeutsche Weinmagazin /1/. The ViniFilter depth filter sheets werenot involved in this investigation, but the ones that were, besidesthe two qualities Beco (contains mineral filtration aids) and Beco-Pad, were the products of the competitors PallSeitzSchenk andSartorius/ Filtrox, as well as sheets of the Czech enterprise Hobra-Sˇkolník (HOBRAFILT), which were also exhibited at INTERVI-TIS. For the classification, the water values stated by the manufac-turers were consulted for which sheet was to be assigned

respectively to which filtration sharpness. Then the filtration testswere carried out with two filter sheets in each case with gradedclarification sharpness. As a conclusion of the investigations, theright choice of filter sheets or sheet combinations, as well as theright gradation of filter stages (prefiltration before sterile filtration)was considered as decisive; qualitative differences between theproducts of the different manufacturers have not been found. Thepure cellulose sheets showed advantages concerning filtration per-

Highlights 2013

F & S International Edition No. 14/2014 23

Fig. 3: New Separator GSC 110 of the ecoplus series, from GEAWestfalia Separator Group

Fig. 4: BECO® LiquiControl2 index measuring instrument to determinewine filterability, from Eaton

Industriestrasse 198669 Veilsdorfwww.inopor.comcontact@inopor.com

Ceramic nanofiltration from Inopor ®

Inopor® is the only supplier of ceramic membranes with a cut-off of 450 Dalton. Ceramic nanofiltration membranes from Inopor® are known all over the world for their reliability in chemical, pharmaceutical and other high-performance applications.

Ceramic filtration and more …

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formance after backwashing, whereby,however, the degree of clarification slight-ly worsened, and moreover they couldscore points through lower drip losses.

The alternative to clarity filtration withsheet filters is crossflow membrane filtra-tion. Its increasing use in wine cellars canbe seen, for example, in the report of PallCorp. that in May 2013 sold its 1,000thunit of the Oenoflow  system, which isequipped with hollow fibre modules. Withthe filtration of Tank sparkling wine aftertartrate stabilization, however, new groundhas been broken in recent times /2/.Tartrate stabilization is particularly impor-tant in sparkling wine because the crystalsotherwise cause uncontrolled foamingwhen you open the bottle. The filtration ofthe abrasively acting crystals succeedswith symmetrical PVDF membranes,while composite polymer membranes andceramic membranes are unsuitablebecause the relatively thin, separation-active layer can be ablated by abrasive par-ticles.

The Italian supplier of wineries, Velowith headquarters in Treviso, is promotingthe third generation of its crossflow filtra-tion systems with a novel modular design.The polysulfone membranes, which arethe centrepiece, are unchanged from theprevious design, but the systems engineer-ing should now allow maximum flexibili-ty. All system components, includingtouch screen control unit, reservoir con-tainers, pumps, containers and dosingpumps for cleaning solutions etc. areinstalled together on the same frame, andindeed equally for all system sizes from 70to 350 m2 membrane area. Here, a group of7 modules with a total of 70 m2 and twocirculation pumps form the basic structure,which, for higher capacities, is supple-mented by appropriate filtration units ofthis structure. The remote control of thewhole system can optionally be carried outvia a modem or the internet.

Furthermore, membranes and mem-brane systems are described in the follow-ing chapter for turbidity filtration, butwhich can be used in principle also forclarification.

Filtration of sediments and fining trub

Crossflow filtration systems, withwhich, besides wine already preclarifiedby sedimentation and/or flotation,  alsomust and wine deposits with accordinglyhigh solids contents are filtered, have onlybeen on the market for a few years. Theyhave the advantage that the filtration ofwines and juices, and also wine extractionfrom the sediments, are possible with thesame system. Some manufacturers alsopoint to the lower oxygen uptake in amembrane system in contrast to a rotarydrum filter. In a study that was carried outat Changins College, Switzerland /3/, theinfluence of such a filtration on the qualityand composition of the end product wasexamined. Used here was an FX3 filtrationsystem from Bucher Vaslin, France, withcapillary modules adapted for this. Thesewere capillaries made of polysulfone with3 mm inner diameter and a nominal poresize of 0.2 μm. The system was equippedwith supply lines of hot and/or cold water,as well as compressed air, and was operat-ed with adapted software for filtrationbackwashing and cleaning. Residues ofsedimentation were treated as a flotationof the same white wine variety of the samegrower, and, for comparison, filtration wasalso carried out with a rotary vacuum filterwith perlites. Although the residues of thesedimentation and the flotation differedconcerning density and viscosity, bothcould be clarified to comparable, very lowdry matter contents, but with significanttemperature rise. With respect to the filtra-tion process, the finished wines were notsignificantly different in their alcohol andacid contents, and only with the polyphe-

nols were there lower values for filtrationunder vacuum, when  the residue of theflotation was considered.

The membranes of the Oenoflow HSsystem by Pall consist of the same mem-brane material and also have the samedegree of separation as the membranes forwine clarification, but the hollow fibreshave a larger inner diameter and thus canprocess liquids with higher solids content.The wine yields should be increased by2% with the application of this system onsedimentation trub. Besides separators anddecanters, the GEA Westfalia SeparatorGroup also presented its enlarged pro-gramme in ceramic membranes under thetradename Membraflow. Here, the config-uration of the ceramic filter elements,modules and also accessories is carried outindividually for the respective application.

With ceramic membranes, high drysolids substances can be achieved withconsistently high flux rates of the filtrateduring the entire life cycle. A typicalexample of use is for beer recovery fromsurplus yeast. Thus, ceramic membranesare obviously also suited for the filtrationof sedimentation trub during wine andjuice production. As an essential advan-tage of these membranes compared withpolymer membranes, the high service lifeis pointed out and with it the low life cyclecosts.

The bandwidth of the availableMembraflow membrane elements consistsof duct diameters of 1.3 mm to 8 mm andpore widths of 5 nm (0.005 μm) to 1.4 μm.Here, the number of ducts ranges from oneup to more than 277 ducts. Also the lengthof the membrane elements can be pro-duced flexibly. Furthermore the GEAWestfalia Separator Group also suppliesmodule casings, back flushing devices andseal accessories.

The Dynamos system of TMCIPadovan, Italy, contains two graded, par-tially interlocking stacks of rotating filterdiscs. It was patented in 2012 /4/ andadvertised at the trade fair both for vinifi-cation and for filtration of apple juice as analternative to vacuum and pressure filtra-tion. An essential aspect which distin-guishes this system from other dynamicmembrane systems is the type of mem-brane lavage to remove outer layers.Besides an automatically controlled back-washing with permeate, during which therotation of the membrane stacks is notinterrupted, nozzles distributed in thehousing provide for tangential flushing ofthe membrane surfaces. At the Oenologycongress, Massimo Pivetta presentedresults from the comparison of the clarifi-cation of sedimentation trub fromProsecco and Merlot with a solid contentof 30 Vol.-% with a vacuum filter, a tubu-lar membrane filter and the DYNAMOSsystem. In all three cases, the same volume

24 F & S International Edition No. 14/2014

Highlights 2013

Fig. 5: Combination of reverse osmosis and perstraction, Memstar method

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was treated. Dynamos had the lowest energy consumption amongthe three process variants, a low temperature increase in compari-son to the filtration in the tubular module and the least consump-tion of flushing water. However, the consumption of cleansingchemicals was a little higher than with both other variations, but tomake up for it, Dynamos gets by without filtration aids, just likethe crossflow system with tubular membranes. In light of the testresults, the determined necessary separation area for 1000 l/h winelees with 30 Vol.-% of solid content was 40 m2 for dynamic filtra-tion, 70 m2 for the crossflow filter and 10 m2 for the vacuum filter.

Technical measures for alcohol management in the wine cellar

How to prevent excessive alcohol levels in white and red winesis the object of a collaborative project funded by Bundes mini -sterium für Ernährung, Landwirt schaft und Verbraucherschutz(BMELV), which is coordinated by Prof. Monika Christmann andVolker Schaefer of the Institute of Oenology of the University ofGeisenheim. In this project viticulture, microbiological and cel-lar  measures are studied. Also the International Organisa tion ofVines and Wines (OIV)supports research projects on this subjectthat were presented within the scope of the Oenology congress. AsVolker Schäfer (University of Geisenheim) explained, the current-ly applied cellar-technical methods for alcohol withdrawal fromwine consist of distillative processes such as the Spinning ConeColumn or vacuum distillation. Possible as membrane processesare osmotic distillation in the membrane contactor, or reverseosmosis with subsequent vacuum distillation or osmotic distilla-tion of the permeate. With reverse osmosis alone, however, part ofthe alcohol is also taken away, but due to reconcentration, theretentate does not contain less alcohol than before in percentageterms. Therefore, the permeate alcohol is withdrawn by vacuumdistillation or osmotic distillation and afterwards is mixed againwith the retentate of the reverse osmosis. More rarely, and notallowed in many countries, is mixing the RO retentate with water.The two-stage process as a combination of reverse osmosis andosmotic distillation was developed by the Australian enterpriseMemstar and was patented. The representation in Fig. 5 is simpli-fied in this respect as it is not shown that the RO permeate is fur-ther degassed and heated prior to entry into the membrane contac-tor. Instead of the concept “osmotic distillation”,  the contactorprocess is also called Perstraction, and it physically concerns theextraction of vaporous alcohol through a hydrophobic membraneinto the extractant water. The process is carried out intermittentlyand the RO retentate and the dealcoholised RO permeate is circu-lated until the desired alcohol reduction is achieved.

Besides the technical methods for the treatment of the finishedwine, there exist newer methods of ultrafiltration and nanofiltrationthrough which the sugar content is reduced in the must before fer-mentation. These methods generally have the disadvantage thatthey can only be applied very quickly, immediately after harvestand must extraction.

According to the resolution of the OIV /5/, the reduction of thealcohol content of a wine is allowed by at most 20%. The endproduct must have a total alcohol content greater than 8.5 Vol.-%(according to the definition of wine). The removal of alcohol fromthe wine cannot be carried out in combination with a change in thesugar content in the must. However, in addition, the possibility alsoexists to produce “Grapevine products with reduced or low alcoholcontent” /6/ (this is by definition no longer wine).

In the research projects discussed at the Oenology congress, thedifferent ways of influencing the alcohol content were comparedand their influence on the ingredients and sensory properties of theproducts was discussed. There is not enough space here to illus-trate in detail the results that have been obtained with differentmethods, in different wine varieties and in different European wineregions. Therefore, some generalised information is summarisedbelow.

The influence of dealcoholisation by up to 2 Vol.-% on the mate-rial composition of the treated wines depends on the dealcoholisa-tion process and on the wine variety. The separation criterion inthermal separation processes is such as the volatility of the respec-tive components in osmotic distillation, and the molecular weightin reverse osmosis. For that reason alone, the application of the ROwith subsequent dilution of the retentate is an unfavourable solu-tion, because thereby important flavouring materials also get lostwith the permeate. But also the other methods of alcohol extractionare associated with low losses of highly volatile aroma compounds,whereby this has not been felt in all cases in sensory testing. If so,then alcohol reduction seems to emphasize the acidity and somebitter compounds, while fruity notes (because of being highlyvolatile) get somewhat lost.

Worth mentioning in this context is the so-called “sweet spot”,which, as far as it is known, could be adjusted with the describedmethods. “Sweet spot” is the alcohol content in which the flavourintensity is particularly high and the wine is therefore judged to bequalitatively outstanding.

Literature: /1/ Burkert, J.; Köhler, H.J.; Hartmann, M.: In die Tiefe gehen – Filtration mit Filterschichten,

das deutsche weinmagazin 4/16, February 2013, /2/ Kahl, S.; Stoll, N.: Innovative Sektklärung – Filtration von Tanksekt nach der

Weinsteinstabilisierung; Getränkeindustrie 4/2013, pp. 34 - 37/3/ Schonenberger, P.; De Giorgi, D., Ducruet, J.: Filtration of grape juice sediments: a new

application for cross-flow filters; Wine & Viticulture Journal March/April 2012, 28 – 32/4/ Bornia, L.: Apparatus and Method for Filtering Liquids, Particularly Organic Liquids; EP 2

326 409 B1, 2012/5/ OIV 2012: Resolution OIV-OENO 394B-2012: Correction of the alcohol content in wines,

see www.oiv.int/6/ OIV 2012: Resolution OIV-OENO 294A-2012: Dealcoholisation of wines, see www.oiv.int

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