Cross-flow filtration has been used for the clarification of wine from the late 1980s, along with the filtration of dairy, sugar, fruit juices and water, for bio-pharmaceutical applications (fermentation broth clarification and purification for the production of amino acids, organic acids, antibiotics, recombinant proteins, vaccines, vitamins, etc) and for the treatment of industrial effluents.
Now, its potential for energy-efficiency has made it an viable technique for the clarification of wine and other beverages.
The crossflow filtration technique
Crossflow filtration uses a selective porous membrane that filters a liquid in order to purify, or clarify it. While in dead-end filtration the circulation of the liquid is not perpendicular to the filter (as in cartridges, plate filters, etc), in cross-flow filtration the circulation is parallel to the membrane. The technique consists in creating a turbulent stream on the surface of the membrane, thus preventing filtered particles to settle on the membrane.
An important aspect of this type of filtration is that it requires little energy to work. Moreover, the quality of the filtration is constant over time because the fouling is reduced. Crossflow filtration is a ‘soft’ process because the filtering is made without any change of state of the filtered element, and never gets distorted. It is also an environmentally-friendly process as no filter aid is used. It therefore has very strong advantages as it drastically simplifies the steps used to process the wine before bottling and it can reduce or eliminate the need for some consumables. In one step, crossflow filtration clarifies the wine, giving it a clear appearance and making the wine microbiologically stable.
Two main types of membranes are currently available: organic membranes made from polymers and inorganic membranes made of ceramics. Most of the systems sold in the last fifteen years incorporate organic membranes, despite their fragility. These systems are based on the geometry of hollow fibres, which, until recently were not available in ceramic. This membrane geometry is very compact, which means that there is a large filtration area for a small volume; it also does not require a large recirculation flow rate, which is important for the lower mixing and heating of the wine.Recently, developments in environmental and health regulations have forced the wine industry to find alternatives to kieselguhr filters. Crossflow filtration is today the unique alternative.
New developments in crossflow wine filtration
New developments in crossflow filtration have led to:
• The manufacturing of ceramic membranes from materials selected for their low polyphenol and polysaccharide absorption characteristics
• The development of ceramic hollow fibres in order to optimize the ratio filtration surface on membrane volume
• The development of a large range of molecular weight cut-offs (pore sizes) in order to suit the different type of wines and filtration purposes.
All these characteristics make the “special wine” INSIDE CéRAM® membranes filter wine in best conditions – both analytically and with regard to flavour.
The traditional advantages inherent in ceramic membranes are also beneficial, and include:
• Mechanical resistance, entailing an extremely long life time and reliability
• Resistance to heat and chemical products even in high concentrations, which is crucial for the cleaning of the membranes
• A strong safety during operation
• Low water consumption and low waste production.
With the evolution of this process, the development of units like the TIS offers new perspectives. The Tangential Integrated System (TIS) is an autonomous module which integrates the housing, the membranes, the circulation loop and the pump, creating a tangential flow. The TIS replaces the entire standard loop, considerably simplifying the systems . The TIS, which is the heart of the VINI-TIS systems, gives new advantages to the tangential filtration and makes it a real oenological tool.
For wine filtration, the TIS offers a higher compactness, reliability and is user friendly. Due to its very low dead volume it increases significantly the filtration yield.
The VINITIS units can also be used for the filtration of musts and lees. This versatility is possible because the TIS is an autonomous module in which the membranes can be changed easily, and because the large range of geometries of the INSIDE CéRAM “special wine” membranes make it possible to adapt to the load and viscosity of the products that need to be filtered. The TIS makes it also very easy to extend the production capacity by the addition of one or more TIS.
The VINI-TIS also makes it possible to replace the two or three kieselguhr filtration steps generally used to prepare the wine before bottling, in reliable conditions and protecting the wine. This system is modular and multi-purpose, making it possible to adapt to the product to treat.
These recent developments in ceramic membranes and processing make crossflow filtration even more attractive for the wine industry. The technological improvements offered by the INSIDE CéRAM® membranes and the TIS have been awarded the gold medal at the SITEVI 2003 (Médaille d’Or au Palmarès de l’Innovation SITEVI 2003).
Optimisation of the TIS
In 2005, SIVAdeveloped a new TIS in order to optimize and develop new crossflow filtration processes to meet the increasing demand of the industries globally and the wine industry in particular for tangential filtration processes. The company's R&D team has created a new generation of TIS in order to satisfy the different requirements of the private producers and cooperatives on one hand, and the large wine bottling companies on the other.
The new TIS-37A replaces the previous versions, which were integrated into the VINI-TIS. The main improvements of this new system include:
• An increase of filtration surface that from 10 to 12 m2;
• Smaller overall dimensions;
• A dead volume reduced by 17%;
• An energy consumption in KW / m2 reduced by 17%;
• A drastic reduction of parts (factor 2).
These developments reportedly bring notable benefits in terms of performance for wine applications, in particular:
• Flow rates per TIS that increase by 20%;
• The entire circulation loop is made only of ceramic membranes: the wine is only in contact with ceramic membranes and is filtered permanently;
• The average transit time of the wine in the TIS is therefore reduced, which reduces the mixing and the respect of the wine;
• An increased yield (lower loss of wine) because of the lower dead volume;
• A consumption of water and cleaning agent, which is reduced even further.
The TIS-37A offers, as a consequence, an improvement on the qualitative aspect of the wine, while saving money, both in terms of investment (per m2 of filtration surface) or running costs (lower energy consumption, higher yield, lower water and cleaning agent consumption).
The TIS-91A develops 30 m2 of filtration surface for each TIS and offers the following additional advantages, when integrated into large capacity systems:
• A lower footprint (15 to 20% less floor space compared with the TIS-37A);
• Simplification of the complete units, for more comfort and safety;
• Reduction of the number of parts per m2 (factor 3 to 4.7);
• Increased resistance and reliability for intense use;
• Cost reduction per m2 for large units, running costs (lower energy consumption, lower water and cleaning agents consumption, increased filtration yield) and maintenance (fewer parts, increased reliability).
SIVAnow offers two new ranges of VINI-TIS, with improved total performances that which suits all the various conditions of use. These depend partly on the market and the type of end-users. For private cellars, the VINI-TIS Private cellar range equipped with TIS-37A offers:
• Low flow rate requirements (100 to 500 hl per day);
• Minimum investment;
• User friendliness;
• Low dead volume given the small size of the tanks to filter (20 to 200 hl);
• Progressive extension of the capacity of the unit (by sections of 12 m2);
• Choice of the VINI-TIS Private cellar range equipped with TIS-37A;
The VINI-TIS Winery range equipped with TIS-91A OENOSOFT option is suitable for large wineries and other companies bottling wine, and offers:
• High flow rates requirements (500 to 1 200 hl or more per day);
• Intensive use and maximum reliability;
• Minimum maintenance;
• Fully automatic and total traceability of the production;
• Extension in connection with surfaces already installed (by sections of 30 m2).