WINE SCIENCE:

Wine Clarification and Stabilization: Providing Clarity on Fining and Filtration

“Sir,

Your Excellency’s Letter of the 6th Inst. did not come to Hand untill the 11th, and the Bottle of Wine to which it refers, and which it was necessary to receive in Order to reply to it with Precision was only delivered to me a few Days ago.—I observe that the Wine in this Bottle was very thick and cloudy; should it have been in this State when You received it from Mr. Olsen I apprehend You will have formed a less favourable Idea of it than it deserves, since it was perfectly bright when it was sent from home. This however does not apply to the Tokay which never fines completely on Account of its Richness.”

-To Thomas Jefferson from Justus Erich Bollmann, 28 February 1803

The Utility and Science Behind Fining & Filtration

Wine cloudiness has been considered a marker of poor wine as far back as can be remembered. However, this may not always be the case. Even wine aficionado and third president of the United States of America Thomas Jefferson had to be reminded that some delicious wines may always show some sediment and we should not judge a book by its cover.

Yet, the processes of clarification and stabilization have become increasingly important as wine consumers, especially preferential white and blush wine drinkers, have developed an expectation that their wines will be clear, bright and without haze. But what really goes into clarification and stabilization? Are these processes necessary, stylistic, dangerous or beneficial? And, since we are focused on anthocyanins and polyphenols here at Healthiest Pour, what are the impact of these methods on the remaining concentrations of these beneficial compounds?

In other words, are wine consumers wrongly focusing on looks over personality when it comes to wine clarification and stabilization? We tend to make the same mistake when we start dating in our adolescence and once we turn the corner to legal drinking age, are we making the same indiscretion with wine?

In this article we will look at:

Basic Definitions of Clarification and Stabilization
Why Winemakers Choose to Clarify and Stabilize
Drilling Down on Techniques: Racking, Fining & Filtration
1. Racking
2. Fining
3. Filtration
What it all means for Wine Consumption

Basic Definitions of Clarification and Stabilization

Wine production does not end with alcoholic fermentation, as there are a number of additional processing steps before bottling. Clarification and stabilization serve as two catch-all categories to describe these processes. In the most simplistic terms, Stabilization can be defined as producing a wine where the physical and sensory characteristics of it will be preserved while it is stored. Because wine is a chemical mixture with many active microorganisms interacting in a dynamic state, stabilization can be an effective method at ensuring wine does not go rancid between the time it is bottled and the time it reaches the consumer. Clarification, on the other hand, is the process of adding a substance to juice or wine to remove certain components that produce a cloudy wine.

An aged – and incredibly delicious – 2001 Chateau Eugenie Haute Collection from Cahors has become caked with sediment along the side of the bottle from the aging process and large amount of polyphenols and tannins left in the unfined wine.

Why Winemakers Choose to Clarify and Stabilize

There are several reasons why winemakers choose to stabilize and clarify wines as part of the post-fermentation process. Wine instability is driven by several factors including (1) residual sugar, (2) excess protein (“protein haze”), (3) excess potassium bitartrate (“wine diamonds”) and (4) residual malic acid in red wines. In order to produce high-quality wines, or at the very least, to create the perception of unflawed wines, winemakers pay attention to stabilization and clarification, considering each of the following factors:

Management of Consumer Rejection – consumers may have quality concerns if sediment or particles are observed.
Prevention of Haze and Cloudiness – in white and blush wines, haze formation is attributed mainly to proteins and potassium bitartrate (cream of tartar) which forms crystals. In red wine, malic acid and phenolic compounds can cause haze.
Removal of off-odors or aroma-distracting compounds.
Approachability of wine at a younger age – stylistically, winemakers may employ techniques to remove tannins and soften wine so that the wine is ready for drinking immediately.
Cutting astringency and bitterness– to appeal to more diverse (or even general) palates, winemakers may extract tannins, anthocyanins, and other compounds (here we should be cautious, because this pulls out the beneficial compounds and reduces aging potential).

Drilling Down: Racking, Fining and Filtering

Racking:

The most natural process for any white, blush or red wine to go through is racking. Racking is the old school method of clarification and stabilization that allows for the settling of sediments using gravity; heavier matter falls to the bottom of the fermentation or aging vessel. As grape matter like seeds and skins, along with dead yeasts (lees), fall to the bottom of the vessel, the wine is then siphoned off to a new container. While this is a natural and inexpensive solution, it requires patience and much time, as it is often repeatedly performed to achieve the desired effect.

For example, white wines are usually racked to remove gross yeast lees shortly after alcohol fermentation is complete. They are racked again after the wine has been hot and cold stabilized (the process to ensure no activities of microorganisms or crystal formation at extreme hot or cold conditions), and a third time just before bottling. In red wines, racking typically does not occur until malolactic fermentation is complete. Some of the fuller-bodied, darker and more pronounced red wines undergo longer aging processes before they are available to consumers. During this time, they could be racked 2-3 times in the first year of aging, and every six months thereafter until they are available for sale.

Fining Practices and Agents:

At Healthiest Pour, we’re not big fans – at all – of fining, as it can pull out many of the desirable and beneficial compounds found, particularly, in red wine. Fining is rarely a selective process, and so while its aim is to remove unwanted substances from wine, it often also extracts qualities like flavor, color and aroma (1).

During our time spent at many Old-World vineyards and red wine producers, our questions about whether they fine their wine is often met with a strange stare in response, followed with the comment “Why would we do that?” We even may have offended one or two wineries with this question, though it is a common, if not overwhelming, practice in the United States. The Old-World wineries we have visited and are advocates for pridefully manage their wines through earlier vineyard practices, racking with possibly light filtration to remove large sediment, but forbid fining. They also note that the addition of materials to their juice can deposit unwanted aromas or alter chemical composition. Furthermore, many fining agents possess allergic potential (2).

So, what are some common fining agents and what is their purpose:

Filtration Practices and Techniques

Filtration is a method of removing unwanted particles, such as grape parts and dead yeasts, that are larger than the filter medium. There are three main techniques. The first is depth filtration, which removes course particles, commonly with diatomaceous earth or cellulose pads. The second is surface filtration which targets finer particulate matter by passing the wine through a thin membrane, which captures particles. Finally, ultrafiltration is used to separate out yeasts and bacteria. However, you will notice that the fining processes progresses from larger to smaller particles. Ultrafiltration pulls out the smallest chemical compounds, and this often means the removal of beneficial polyphenols, including flavoring, aroma, and color compounds.

As a result, most skilled winemakers apply filtration for white wines, and less often in red wines. In fact, while filtration can pull out lactic acid bacteria and active yeasts in white wine lending to its clarity and stability, it is important to note that in many darker red wines, they are seldom phenolically-stable. That is the beauty of these red wines, that they remain dynamic in the bottle, and continue to evolve as they age.

What it all means for our Wine Drinking

Hopefully at this point you know enough to start producing your own quality wines, unfined and chock-full of polyphenols. Let’s dig a little deeper into the nitty-gritty details of what stabilization, clarification, racking, fining and filtration mean by answering three major questions.

1. Are these processes even necessary?

By this point, you have surely asked yourself this question. Stabilization and clarification are considered a necessary part of winemaking, but exactly how to implement them remains part of the art of winemaking. It is necessary to remove any unwanted characteristics and impurities without disrupting the wine’s appeal, and to that end, wine makers experiment with many different clarification and stabilization tools on small wine samples before applying it across their entire harvest of pressed and fermented juice.

In white and blush colored wines, stabilization and clarification are considered more essential. Sediments, crystallization and unintentional secondary fermentation/undesired effervescence can result if these practices are not put in place, signaling to the consumer that the wine was improperly finished, or even of lower quality.

In red wines, on the other hand, stabilization and clarification are less necessary. In fact, other than racking, the natural process allowing solids to fall out of solution, many skilled winemakers will not proceed with other fining agents and filtration techniques. This is mainly because those techniques can remove color, aroma, mouthfeel, and aging potential in the wine, which could all signal a lower quality wine. These processes can actually strip red wine of the compounds that make it so enjoyable, and luckily, many of these components are the same that may provide a health benefit in wine (3).

2. What about allergic reactions to fining agents?

The scary thing about fining is that the average wine drinker is unlikely to even be considering the effect it may have on his or her health. Furthermore, the average wine drinker may have food allergies or dietary restrictions based on personal, religious, or cultural beliefs, and by drinking wine, they may actually be unknowingly violating them.

Take, for instance, the short-list of the most common fining agents listed above. Most of us know someone who has an allergy to eggs, shell-fish or other seafood. Or, we all have that vegan or vegetarian friend who is nearly impossible to meal plan for but definitely likes slugging down a glass or two of wine. Yet, chances are that the wine is not vegan or vegetarian-friendly.

Traces of fining agents can remain in wines despite even the most careful winemaking procedures, and so there is a chance for exposure to allergens or proteins that are directly at odds with one’s dietary practices. Wines are not typically required to be marked with a label indicating that animal products are used, so it is important to do diligence if this is an issue for you. (And we can help with that too!)

3. What is the impact of these techniques on the concentration of beneficial compounds in wine?

This is, of course, the most important question. The short answer is that clarification and stabilization are necessary to remove any harmful bacteria, yeasts and even pesticides from the vineyard (the latter which, hopefully, more vineyards start avoiding), but fining and filtration have the ability to pull out the potentially beneficial anthocyanins, tannins and other important polyphenols in wine (4). Fining can remove many of the antioxidant-producing flavonoids. For instance, quercetin, most known for its potential cardiovascular benefits, is removed from fining with gelatin, casein, and PVPP (5). In fact, PVPP in combination with casein reduces total polyphenols by almost 25%, decreasing the sensory character of the wine, and reducing potential health benefits in the process (6).

Filtration, which removes solids and sediments, also has the potential to extract phenolic compounds, though to a much lesser degree. Generally speaking, wine makers can control the size of the filter used to remove things like lactobacillus and Brettanomyces, while preserving the smaller compounds like anthocyanins and phenols.

In Summary

We hope this article shed light on the vital, yet rarely considered, stage of winemaking and provided some insights into the importance of post-fermentation processes. For the red wine drinkers out there trying to be most thoughtful about what they drink, we hope this article explained the reasons why fining and filtration can be beneficial when used appropriately, but disastrous when overused. Good winemakers are generally able to produce a delicious and polyphenol-packed wine through basic stabilization processes and do not have to rely on fining and filtration.

As a result, these skilled winemakers leave us with a red wine full of all the components that make a red wine, well, red. And flavorful. And pleasing to at least four of our five senses. And biologically-active in our bodies.

A skilled winemaker in Italy summed this all up quite nicely for us while discussing his vineyard and winemaking practices:

“Wine is alive…and if you fine and filter and use all these unnatural processes then the wine cannot be dynamic.”

REFERENCES:

1. Castro, R. I. et al. New polymer for removal of wine phenolics: Poly(N-(3-(N-isobutyrylisobutyramido)-3-oxopropyl)acrylamide) (P-NIOA). Food Chem. 213, 554–560 (2016).

2. Marangon, M., Vincenzi, S. & Curioni, A. Wine Fining with Plant Proteins. Molecules 24, (2019).

3. Champ, C. E. & Kundu-Champ, A. Maximizing Polyphenol Content to Uncork the Relationship Between Wine and Cancer. Front. Nutr. 6, 44 (2019).

4. Sen, K., Cabaroglu, T. & Yilmaz, H. The influence of fining agents on the removal of some pesticides from white wine of Vitis vinifera L. cv. Emir. Food Chem. Toxicol. 50, 3990–3995 (2012).

5. Dabeek, W. M. & Marra, M. V. Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans. Nutrients 11, 2288 (2019).

6. Ghanem, C. et al. Analysis of the impact of fining agents types, oenological tannins and mannoproteins and their concentrations on the phenolic composition of red wine. LWT – Food Sci. Technol. 83, 101–109 (2017).