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    Published on: 01/31/2024

Membrane contactors in wine production and bottling

Maria Ramirez and Norbert Selzer, 3M HealthCare Germany Gmb

1 3M HealthCare Germany GmbH, SPSD, Öhder Str. 28., 42289 Wuppertal, Deutschland

Contact:  Norbert Selzer, nselzer@solventum.com  
For more information 3M Food and Beverage | Filtration for Wine

Abstract: Systems for gas management using membrane contactors are increasingly being used in wine production and bottling. Compared to conventional procedures, there are savings in process time and auxiliary substances and tight market requirements, for example the CO2 content, can be met more reliably. However, there are special requirements for membrane cleaning and partly for the control of the systems. In a special mode of operation, it is also possible to reduce the alcohol content in wine or the sulfur dioxide content in juices.

Key-words: Membrane contactor, Wine, Gas Management, Oxygen, Carbon Dioxide, Alcohol 

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Membrane contactors have been increasingly used to treat liquids for nearly 3 decades [1]. They are state-of-the-art today, especially in many areas of water treatment, including the production of ultra-pure water for pharmaceutical applications. They are also used in various areas of beverage industry. 

1. Gas management in oenology

1.1    Initial situation

Oenologists have been aware for decades of how important dissolved gases are in wine. In most of red wine, the carbon dioxide (CO2) content should be low. Lively, white wines tend to have an increased CO2 content and even higher CO2 levels are characteristic of sparkling or semi-sparkling wines.  

In comparison to CO2, that is generated during fermentation process, oxygen (O2) is coming from atmosphere in contact with wine and leads to oxidation of wine ingredients. It has a more indirect, time-delayed sensory effect on wine, significantly influencing aging behavior. 

With traditional methods used in winery operations, resources are often not used economically, and the desired concentrations of gases can be set inaccurately, sometimes even leading to an undesirable oversaturation of nitrogen (N2). 

1.2    Gas management using membrane contactors

Over the last few years, membrane contactors are increasingly used for gas management in wine treatment plants [2-7]. Membrane contactors can influence several gases in one step [8]. 

Figure 1 shows a typical gas management system with membrane contactors. The wine feed splits into two in parallel connected contactors, while the sweep gas line, also connected in parallel, flows in counterflow. The gas outlet ports are connected to a vacuum pump. Overall, system's efficiency can be controlled by adjusting the vacuum level and/or sweep gas flow. 

Furthermore, Figure 1 illustrates how O2 is transferred from the wine to the gas stream. At the same time, if CO2 is used as a strip gas, its concentration in wine can either be increased or reduced.  

Figure 1. Wine treatment system with 3MTM Liqui-CelTM Membrane Contactors

1.3    Principle of operation

For wine treatment, hollow fiber membrane contactors are used because of their high packing density and orderly flow pattern. The membrane material used is so hydrophobic and the pore size so small that the pores are not wetted by the pressure of the wine and remain filled with gas. 

An example of such a membrane contactor is shown in Figure 2.

The contactor contains a capillary membrane cartridge, wound on an inner tube with holes, through which the wine flows. By means of the holes, the wine flows radially around the hollow fibers from the center outwards. The baffle positioned in the center deflects the liquid back into the tube, thus ensuring a homogeneous contact with the capillaries along the entire contactor. 

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Figure 2. Schematic representation of 3MTM Liqui-CelTM Membrane Contactors [1].


Counter-current on the lumen side a sweep gas is introduced, and a vacuum can be applied. This creates a concentration gradient between the wine phase and the gas phase, which drives transfer of dissolved gases from wine to the gas phase. According to Henry's law, the concentration of a gas dissolved in wine is proportional to the partial pressure of the gas in contact with the wine. The proportionality factor, called the Henry coefficient, is gas specific and temperature dependent [9]. Figure 3 compares Henry solubility coefficient for different gases at 10 °C and 50 °C. In membrane contactors, large exchange areas can be accommodated in a compact device. The gas volume required in the hollow fibers (internal diameter approx. 0.2mm) is small and the diffusion path for the dissolved gases through the liquid phase is short. Because the liquid and gas pressures can be adjusted independently, gas exchange can take place in-line. The efficiency can be regulated by adjusting gas pressure level (positive or negative) and/or sweep gas flow. 

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Figure 3. Henry solubility coefficient for various gases at 10 °C and 50 °C 

 

1.4    Reasons to use membrane contactors for gas management

Porous injectors are traditionally used for gas management in wine production. By means of this technology bubbles of gas are injected, for example N2 for oxygen removal or CO2 to enrich or adjust its concentration, and consequently gas exchange will occur at the surface of the bubbles [10]. Typically, when working with injectors, the adjustment of the different gas concentrations must happen one after the other. Additionally, inerting steps for the tanks with N2 are required to avoid atmospheric oxygen transfer to the wine. 

As early as 2011, A. Blank [10] determined in a comparative study to what extent the use of gases can be reduced by using membrane contactors. The study compares both technologies, aiming to add CO2 to a defined concentration while reducing O2. Porous injectors were run in two steps: first step by applying nitrogen for O2 reduction and for the second step CO2 was added to readjust CO2. The membrane contactors were operated by combining CO2 as a sweep gas and applying vacuum to the other end of the membrane lumen. 

The major difference between the two methods is the gas consumption, as shown in Table 1. 
 

Table 1. Comparison of gas use with traditional and gas management using a membrane contactor [9].

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Further advantages for the winery operation or the wine bottling with membrane contactors are:

  • saving process time by executing several steps at the same time (O2 reduction while CO2 adjustment)
  • avoiding undesired supersaturation with nitrogen
  • complying with narrow specification values for wine gas concentration (especially CO2


Moreover, gas management systems can be arranged at different points in the process:

  • when unloading from a truck into a tank or from a tank into a shipping container 
  • when pumping from tank to tank 
  • directly in the filtrate flow of a Cross-Flow filtration system 
  • directly upstream to a bottling plant 


Directly upstream to a bottling plant may be the most challenging of all previous options. It is influencing the final product without any buffer. The bottling line itself is often generating short time fluctuations in flow rate. Therefore, at this point the highest level of control technology is required. 

Precise CO2 sensors today usually still work with a considerable dead time in relation to the rather short-term flow changes that result from the operation of a bottling plant. Individual system manufacturers have developed advanced regulation and control concepts for this. The company Ymelia from France has patented a combination of membrane contactor with a cascade control (gas concentration à gas pressure) [11]. 

For speed reasons, the company KH-tec from Germany [2] does not rely on a typical feedback control, but on a calculation concept for the process variables based on a large number of measurement data with an implemented fouling factor for the membrane condition. 

At the other process locations, simpler control technology is can be sufficient. Manual systems are also used, especially in smaller operations [12]. 

It is quite common that small wineries do not install the processing and bottling lines in their own facilities, instead they outsource them to service providers with mobile systems [13]. 

2.    Membrane cleaning

Compared to the use in pure water, cleaning is much more relevant when using membrane contactors in wine. Certain cleaning steps are carried out regularly, especially after the end of an operating phase, such as before process shutdown. Maintaining the membrane contactors is important or very undesirable odor or taste changes can occur from wine residues due to microbial conversion. Given the membrane and contactor materials employed, the entire pH range can be used for cleaning, even at elevated temperatures (typically 40 - 60°C). Regular oxidative cleaning should be avoided to prevent shortening the membrane service life.  

Most importantly, any chemical cleaners used must not contain even small traces of surfactants, because they would cause wetting of the hydrophobic pore membrane. Moderate use of oxidants can already lead to a decrease in the hydrophobicity of the membrane surface. In the early oxidation stage, such membrane may not allow passage of water through (leak) but may show leakage when operated with wine, which has a slightly lower surface tension due to the alcohol content. As oxidation progresses, the hydrophobicity is no longer sufficient to retain even pure water, or fiber breaks occur due to the decreasing mechanical strength of the microporous structure. 

Another special feature of wine use is the need to clean the lumen of the hollow fibers at regular intervals, since even the slightest traces of vapor-volatile ingredients in the wine may otherwise act as nutrients for microbial degradation.  

Over time, certain wine ingredients can lead to a wetting effect, that may be overcome by an appropriate operational management (cleaning regime). Some plant manufacturers regularly use partial drying with gas (air) flow through the pore structure, sometimes combined with the cleaning. 

3.    Liquid/Liquid-applications 

In addition to gas management, there are also applications in which instead of gas a liquid is used on the secondary side of the membrane, leaving only the membrane pores themselves gas filled. This allows ingredients with a very high solubility, such as alcohol (see Figure 3), to be removed from the wine. 

3.1    Adjusting the alcohol content

As a result of climate change, several cultivation areas have been producing grapes with an increased sugar content in recent years, which in the fermentation process leads to alcohol levels that are atypical and undesirable for the respective wines. Furthermore, individual countries' tax regulations may also result in wine producers attempting to fall below certain alcohol content limits. 

Cellar masters seek a method to adjust the alcohol content in wines as gently as possible. For this purpose, membrane contactors are used in a per(s)traction mode with a water flow on the secondary side [14]. 

Figure 4 (a) presents a typical process flow diagram. Wine and water streams flow in counter-current to maximize the alcohol transfer rate. The degree of alcohol reduction is adjusted for a given membrane area and temperature by the relation between wine and water flow rate. Temperature can be regulated by a heat exchanger.  

Deepening into what occurs inside the membrane pores, Figure 4 (b) illustrates alcohol vapor transferring into the water stream. As secondary effect, a small amount of water vapor is transferred into the wine. To prevent increasing oxygen content in wine, water with a correspondingly low oxygen content should be used. 

Figure 4. Adjustment of the alcohol content using a membrane contactor

 

3.2     Sulfur Dioxide Removal from juice 

A new membrane contactor application was introduced by KH-tec a few years ago [15]. This is about reducing the sulfur dioxide (SO2) content from the sweet reserve or must. Thermal processes are traditionally used for removal of sulfur dioxide. At temperatures >100 °C, however, there are undesirable changes in taste and the process consumes a large amount of energy. 

Membrane contactors enable effective sulfur dioxide removal at significantly lower temperatures in TransMembrane ChemiSorption (TMCS) operation mode. The figure 5 illustrates an enlargement of a hollow fiber and the chemical reaction that occurs between the SO2-rich sweet juice or must outside the capillary in contact with NaOH through the secondary phase. Sulfur dioxide diffusing through the pores reacts immediately with NaOH, and therefore concentration of dissolved SO2 in NaOH solution is essentially zero, forming a sodium sulfite (Na2SO3) solution out of the secondary phase. 

Figure 5. Principle of the TransMembrane ChemiSorption for sulphide removal

4.     Regulatory Aspects 

Wine production is subject to various food law regulations. 

Gas management using membrane contactors for oxygen and carbonic acid is recognized as a method in Oneo 499-2013 of the "International Code of Oenological Practices" (OIV). The membrane devices themselves must be FDA approved or EC1935 within the EU for use with alcoholic beverages. 

Various criteria regarding the suitability of membrane contactors for organic wine production are under discussion. The technology is based on a general physical principle, the exchange of gases to establish the Henry equilibrium, which also occurs in many places in nature. There is neither a chemical reaction nor any influence from a synthetic material. The membrane only serves to define the boundary between the gas and liquid phases. Due to its hydrophobic properties, it is not wetted by the wine at all. 

Furthermore, from our point of view, this process is preferable because it preserves the true nature of the wine unchanged, while avoiding undesirable effects of other processes already approved for organic wine, such as nitrogen oversaturation. The membrane process minimizes the consumption of auxiliary gases with moderate consumption of electrical energy. Gas management using membrane contactors allows oenologists to obtain the desired quality of the wine without the drawbacks of traditional processing methods. 

Note that currently partial removal of alcohol is prohibited under the EU regulation for organic wine production [16]. 

5.     Summary

Gas management using membrane contactors offers various economic and organizational advantages for wineries and bottling plants. Compared to other practices and methods, it can be classified as gentle on the quality of the wine product and likewise resource-conserving. 

Various system manufacturers specializing in this field have developed equipment concepts that enable uncomplicated and reliable integration into the oenological operation through adapted control and cleaning strategies. 

Essentially starting from Europe, wineries around the world in the different growing areas are equipped with membrane contactor systems. 

 

For more information or for a technical consultation:

Norbert Selzer
Market and Application Development Manager EMEA
nselzer@solventum.com 

Separation and Purification Sciences Division
3M Food and Beverage | Filtration for Wine

 

6.     Literature

[1]     “3MTMLiqui-CelTM Advanced Dissolved Gas Control” (2023), 3M, https://www.3m.com/3M/en_US/liquicel-us/, May 31st, 2023.

[2]     “Wine / drinks technology”, (2023), KH-tech GmbH,  https://www.kh-tec.com/en/wein-getraenketechnik.php , May 31st, 2023.

[3]     “Romfil Gas Contactor”, (2022), Romfil GmbH, https://romfil.com/cms/other-solutions/romfil-gas-contactor/ , June13th, 2023.

[4]     “EquilibriO2”, (2023), VINEXT SRL, https://www.vinext.it/en/engineering/equilibri02/ , June13th, 2023.

[5]     Experti Srl, https://experti.it/chi-siamo/ , June13th, 2023.

[6]     Imeca Process Accueil - Imeca Process, ensemblier et spécialiste des techniques séparatives. (imecafrance.fr), June13th, 2023.

[7]     “MMR-Plus”, (2018), Juclas Advanced beverage systems, SMART MANAGEMENT OF WINE GASES - JUCLAS, June13th, 2023.

[8]     L.Mondot, J-C.Vidal: Bibliography on the dissolved gases management by membrane contactor in enology  ,  Internet Journal of Viticulture and Enology https://www.infowine.com/it/articoli_tecnici/gestione_dei_gas_disciolti_in_enologia_mediante_contattore_a_membrana_stato_dell_arte_sc_17648.htm

[9]     R. Sander: Compilation of Henry’s law constants (version 4.0) for water as solvent, Atmos. Chem. Phys., 15, 4399-4981, 2015

[10]   A.Blank, J-C Vidal: Development of a membrane contactor for the exact management of dissolved gases, ResearchGate 341985842, 2011

[11]   WO 2016/193586 A1:  Device for adjusting the concentration of a gas in a liquid.

[12]   “Membran Contactor”, (2021), G.A. KIESEL GmbH https://www.kiesel-online.de/download/membran-contactor/ , June13th, 2023.

[13]   “Gestão de Gases”, (2021), Wine On Wheels (WOW), https://wow.com.pt/gestao-de-gases/ , June13th, 2023.

[14]   “MASTERMIND® REMOVE”, (2018), Juclas Advanced beverage systems, https://www.juclas.it/index.cfm/en/products/mastermind-remove/, June13th, 2023.

[15]   “SO2 Membrane System”, (2018), KH Tech GmbH, https://www.kh-tec.com/de/so2-membran-system.php, June13th, 2023.

[16]   “Commission Implementing Regulation (EU) No 203/2012 of 8 March 2012 amending Regulation (EC) No 889/2008 laying down detailed rules for the implementation of Council Regulation (EC) No 834/2007, as regards detailed rules on organic wine”, (2012), Document 32012R0203, https://eur-lex.europa.eu/eli/reg_impl/2012/203/oj , June13th, 2023

[17]  Ramírez, M., Selzer, N., (2023), Membrankontaktoren in der Wein-Herstellung und -Abfüllung

(Kellereitechnik / Önologie, F&S Filtrieren und Separieren, 05/2023, https://www.vulkan-shop.de/f-s-filtrieren-und-separieren-05-2023

[18]  Ramírez, M.  (2023), Membrankontaktoren in der Wein-Herstellung und -Abfüllung (Kellereitechnik / Önologie. [Power Point presentation]. Deutsche Gesellschaft für Membrantechnik- (DGMT) Tagung 2023, Membranen in der Lebensmittel- und Pharmaindustrie.  28 February 2023, Kassel, Germany. https://dgmt.org/newsreader/dgmt-tagung-2023.html

Published on 04/03/2024
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