Filtration of wine is a complex process, requiring precision to achieve the desired quality and safety. It removes unwanted particles, microorganisms, and impurities that can stabilize the wine and preserving its unique character. The filtration process includes steps tailored to different wine types and production stages. For instance, clarification filtration removes yeast and particulates early to protect downstream filters, while final filtration ensures microbiological stability by eliminating yeast and bacteria, preventing cloudiness or off-flavors.

For wineries of all sizes, choosing the right filtration solution can ensure a high-quality product that meets storage and taste standards.

Importance of Filtration in Winemaking

Filtration is fundamental in winemaking. During fermentation, wine contains impurities like particulate matter, yeast, and bacteria that affect clarity, flavor, and shelf life.

Enhancing Appearance and Flavor

Effective filtration enhances wine’s appearance, prevents unwanted flavors, and maintains microbiological stability. For example, cross-flow filtration employs a semipermeable membrane to filter fine particles and prevent clogging, making it ideal for continuous production.

Optimize Wine Quality and Safety

Pre-filtration and sterile filtration are tailored to each wine type to preserve its unique qualities. Pre-filtration removes large particles, while final filtration eliminates spoilage-causing microorganisms in bottled wine.

Depth filters made of cellulose or diatomaceous earth are well-suited for red wines, trapping larger particles and enhancing stability without altering flavor. Cartridge filters, with adaptable pore sizes, offer versatility for pre- and final filtration, supporting both small and large-scale production.

The Process of Wine Filtration?

Wine filtration ensures the final product is visually clear, safe, and has an enhanced shelf life. Filtration in winemaking typically involves multiple stages, each targeting specific types of contaminants to achieve the desired clarity and quality.

Rough Filtration

This first step removes large particles, such as grape skins, seeds, and other debris. Usually done shortly after fermentation, rough filtration prepares the wine for finer filtration steps, typically using coarse bag filters or large-pore filters. It is initial stage removes large particles like grape skins, seeds, and other debris. Often done shortly after fermentation, rough filtration clears the way for finer filtration steps. Typically uses coarse bag filters or large-pore filters.

Polishing Filtration

Polishing filters further refine the wine by filtering out smaller impurities and enhancing clarity, making the wine more visually appealing for bottling. This stage uses polishing filters or fine membrane filters.

Sterile Filtration

In the final stage, sterile filtration removes any remaining yeast or bacteria to prevent secondary fermentation in the bottle. Sterile filters or 0.2 micron membrane pleated filters are employed in this stage.

What is Needed to Filter Wine?

Wine filtration involves passing the wine through different porous media that vary in several key properties:

• Porosity: Refers to the ratio of the empty spaces to the total volume of the filtering medium.
• Permeability: Measured in Darcy, it defines the ability of the filter material to allow liquids to pass through.
• Filtration Cycle: The phase between the start and completion of the filtration process.
• Filling: Occurs when solid particles accumulate on the filter medium, forming a deposit that reduces its permeability.
• Retention Capacity: The filter medium’s ability to trap particles that are larger than its pores.
• Flow Rate: The volume of liquid passing through the filter over a set period.
• Turbidity: A measure of the effectiveness of the filtering medium in terms of its functionality.

Main Filtration Techniques in Winemaking

Several filtration techniques are commonly used In winemaking, each offering unique benefits depending on the needs of the winery. Here, we explore three main filtration techniques: Deep Filtration, Cross-flow Filtration, and Membrane Micro-filtration.

1. Deep Filtration

Deep filtration is a well-established technique in the wine industry, typically achieved through filter sheets or cartons. These sheets, made from a mix of cellulose or cotton fibers, granular materials like kieselguhr, and sometimes cationic resins, act as the filtration medium. The filter sheets are placed between two perforated plates, allowing the wine to pass through while trapping unwanted particles. This method is widely used due to its effectiveness and relatively low cost.

An alternative to traditional filter sheets is lenticular modules. These are designed for deep filtration, offering a more advanced and hermetically sealed solution. Lenticular filters provide highly efficient filtration by using stacked filter layers within a module, ensuring consistent results and reducing contamination risks. Additionally, biodegradable and compostable cellulose filter layers are becoming more popular, aligning with sustainability goals in modern winemaking.

2. Cross-flow Filtration

Developed in the 1980s, cross-flow filtration is one of the most advanced methods available for wine filtration. This technique utilizes membranes, either organic or inorganic, to separate particles from the wine. What sets cross-flow filtration apart is that the wine flows parallel to the filtration surface, rather than being forced through it. This configuration significantly reduces the build-up of particles on the membrane, improving the overall efficiency of the process.

3. Membrane Micro-filtration

Membrane micro-filtration is another sophisticated technique used in winemaking. This method separates liquids by passing them through a selective barrier, known as the membrane, which allows only certain particles to pass through. For wine filtration, membranes are typically made of PES (polyethersulfone), nylon, PVDF (polyvinylidene fluoride), or PTFE (polytetrafluoroethylene). These membranes offer excellent resistance to pressure.

Since the liquid flows directly through the membrane, clogging can occur. Therefore, membrane micro-filtration is generally preceded by pre-filtration steps, such as cross-flow filtration or deep filtration, to remove larger particles before the final filtration.

Organic and inorganic membranes

Organic membranes are typically made from polymeric materials like plastics and synthetic fibers. Common types include PES, which is resistant to pH changes and high temperatures but not suitable for high pressures or cleaning solvents. Another type is PVDF, which is highly heat-resistant and safe for food contact.

In contrast, inorganic membranes are composed of ceramic materials with filter layers that have decreasing grain sizes. These membranes offer significantly greater mechanical strength than organic membranes. They can also be cleaned and sanitized with harsh chemicals and offer flexibility in selecting porosity levels and performing steam sterilization. However, because temperature changes can damage them, careful installation and maintenance are required.

Conclusion

Wine filtration must be viewed as an integrated process, where each stage impacts the next. Each step should be handled properly, following the correct order. The right filters must be used at every stage to ensure effective filtration.

With over 10 years of experience in wine filtration, Sanitek Filter is well-equipped to assist. Contact us to learn more.