As most winemakers tell us, no two wines are alike, and as such, no two winemaking processes are alike in their steps or methods. Wines are commonly broken down into five main families - reds, whites, rosés, sparkling, and dessert - and from there, over two hundred individual types each with their own functional or artistic differences in how they're produced. Wines are often compared in terms of their quality, but what does that really mean given the hundreds of varieties multiplied by dozens of winemaking methods? Many things, in fact, and one key quality metric centers on wine clarity, impacted by all the different ways that winemakers apply clarification techniques through their processes. In this article, we'll discuss the role of clarification in winemaking, the different filtration methods involved, and the related filtration opportunities useful towards achieving premium quality wine.
Let’s set the stage with a few terms to start:
• Wine Clarity refers to the relative turbidity of wine, describing how clear or opaque a wine is in passing light. Clear, uniform, particulate-free wine is typically desirable, but that of course is a matter of opinion and style.
• Clarification is any process or technique that impacts wine clarity, typically removing particulates while homogenizing appearance through mechanical, chemical, thermal, or biological means.
• Filtration is a subset of clarification that uses mechanical devices to capture and remove particulates, bacteria, microorganisms, suspended solids, and even some dissolved solids from wine.
Some winemakers will state that premium clarity wine can be achieved through very tight control of upstream pressing, racking, and settling steps. Others will say that fining is all that is needed (fining is a process of introducing chemical agents into the wine that will organically bind and either precipitate-out or bind-in offending particulates). When additional clarification is desired, mechanical filtration is the next option.
Filtration Approaches in Wine Making
Imagine for a moment all the creature components floating around in wine during its production. Throughout the process, we can find relatively large fruit particles left over from the original grapes, yeast spores from fermentation, trace fining agents if used, sugars, and acids. If that weren’t enough, we also have any unintended foreign containments such as trace elements from process equipment (hose strands, gasket residues, etc.), minerals, inorganics, bacterial, other microorganisms, barrel fibers, and any number of elements coming from ambient air and water.
Down at this scale, you can picture that we need to target particulates by their size, often ranging from 150 micron for initial media filtration, all the way down to 0.45 micron for sterile bacteria removal. This helps make the case that filtration in winemaking is strategic to the risk factors being targeted, which impacts the filtration method, media, efficacy, and cost involved.
Filtration solutions can be broken down into the below technologies:
• Plate Filtration - for general stabilization and particulate removal, a plate filter is a great selection balancing cost and filtration potential. Plate filters utilize multiple fiber-media sheets (or pads) clamped together in a plate-and-frame arrangement, achieving large surface areas and flow rates. Plate units are great for their simplicity, frequent change-over potential, and overall flexibility, but can be difficult to use for extremely tight filtration, can easily entrain air that fouls wine, and can also be wasteful due to using disposable filter sheets.
• Housed Filtration - an advancement over plate filtration, housed filters utilize stacked disc or cartridge style filter elements in fully enclosed housings that offer tighter filtration potential, higher flowrates, better cleanability, and virtually no air entrainment. Large systems can include multi-plex filter housings operating in parallel, serving all uses from general clarification down to final sterile filtration.
• Diatomaceous Earth Filtration - a form of algae, diatoms are the skeletal remains of single-celled organisms that naturally form extremely small, porous structures which serve to reliably filter out microscopic particulates. DE filtration has been used in food and beverage applications for nearly a century, being quite low tech and reliable, but requires moderate maintenance and consumable DE media. This technology is a great option for small batches and a wide range of filtration goals, though is largely being replaced in larger operations due to having limited throughput.
• Membrane Filtration - using advanced microfiltration membranes that operate on the principle of selective permeability, wine can be filtered across the full spectrum of target particulates and flow rates. Further, custom systems can be designed with modular, progressive, and/or multi-pass filtration, offering substantial flexibility at full production scales. Membrane systems are costly and require aggressive in-line cleaning, so may only be viable for large manufacturers.
Total Quality Management in Wine Filtration
Now that readers have a general perspective on effective filtration methods found in winemaking, how can we best apply these solutions? Also, what else do we need to know when making filtration selections? Our answer: the principles of Total Quality Management tell us that all manufacturing aspects relate to each other. With respect to wine filtration, looking at complete filtration opportunities across the winery is the best way to manage risk and bolster finished product quality overall. A few key considerations here include:
Select for the Application, Not for Features
Automated membrane systems might provide all the bells and whistles imaginable, but if your objective is simply to remove fining agents or fermentation spores, you'd be better served by a simple plate filter set up for that one specific purpose.
Design Standards
For any filter equipment that contacts wine or human-consumed ingredients, make sure that equipment complies with hygienic, food-grade design standards such as NSF or 3A. Materials should be stainless steel type 304 or 316, or similar food-grade selections that will not harbor bacteria, will not react with or contaminate products, and can tolerate food-grade, high-temp cleaning chemicals.
Byproduct Filtration
Aside from wine filtration itself, other process streams may benefit from filtration. Good examples include lees filtration to recover usable wine volume, waste filtration to separate solids for composting, and off-grade wine filtration for beneficial secondary processing (such as distillation).
Utility Service Filtration
Compressed air, water, steam, nitrogen, and other utility services should receive proper filtration to protect against wine contamination. These utilities can be sources of bacteria, viruses, minerals, and other contaminants that can present food-safety risks. Water is of specific concern since it's routinely used either in batching or cleaning wine-contact equipment.
Ventilation Air Filtration
As food safety awareness grows throughout the food process industry, ambient air is increasingly scrutinized for bringing in particulates, bacterial, VOCs, and other contaminants that may land on food-contact surfaces or containers. HVAC systems should be evaluated for their risk factors, especially those that serve final bottling areas, and even more especially for facilities located in high-risk locations such as in heavily populated industrial areas with lots of surrounding emissions.
Navigating the Vineyard of Clarity
With so many filtration options and technologies available, the dilemma is determining which fits perfectly within your unique winemaking tapestry. Each filtration method, whether simple plate filtration or advanced membrane systems, serves a unique purpose, designed to cater to the multifaceted world of wine.
It's essential to remember that wine filtration is not a one-size-fits-all endeavor. It's about recognizing the individual needs of each wine type, understanding the interconnected quality aspects, and choosing the right tools for the job. So, as you contemplate the nuances of wine clarity and filtration, know that the answers lie in the delicate balance of art and science, tradition and innovation, all converging to amplify the wine's story.