Wine – more than just fermented grape juice?

The Incogvino SuperFANS are all about the wine, and not just the tasting and the drinking. Being an inquisitive bunch, the following question popped up on our mailing list this week. “Egg protein? Milk protein? Is this normal?” with reference to a wine label with the aforementioned listed on it.  This brought up the topic of fining agents and the question of not only what, but how, these processing aids are used in the making of wine. The science of fining agents can be quite complicated (some Chemistry 101: the molecules of fining agents have either positive or negative charges which affect the way they interact with the compounds in wine, which also have positive or negative charges. Science!) but the basics can be simple to understand. Here’s a quick clarification about fining agents in wine.

Let’s start by looking at why fining is important in the first place. When evaluating a wine, either formally for scoring or just looking at the liquid you’ve just poured into your glass, the preference is always for clarity. Clear wines are generally associated with quality and a healthy wine. Cloudiness could even indicate a fault in the wine, such as the growth of yeast or bacteira. Of course there are wines made in unfiltered styles which may present as hazy, but the majority of wines are filtered and clear.

Sediment at the bottom of a wine barrel.

Sediment at the bottom of a wine barrel.

Fining agents work to clarify wine by binding to the insoluble particles in wine which cause the murkiness. The process causes these substances to precipitate out of the wine in a solid state and settle at the bottom of the tank. Fining can also remove unwanted soluble compounds, such as phenols, polymerised tannins and other proteins as these will precipitate into an insoluble state upon binding with the fining agent. The clarified (fined) wine can then be separated from the insoluble material through a process called racking (removing the clear wine from the top and leaving the unwanted material at the bottom).

Now that we know why we use fining agents and how they work, let’s have a look at the types of compounds used in this process. Different fining agents are used depending on the type of wine. Some agents are more severe than others and can strip the wines of flavour and aroma compounds, so a balance between removing all unwanted substances and preserving desired ones is always important for winemakers to achieve. Some of these fining agents may seem fantastically odd, but keep in mind that they never actually form part of the wine – they are not food additives but rather processing aids – and precipitate out, separated completely from the wine that ends up in your bottle.

One of the most commonly used fining agents is bentonite, a type of clay. It is a very effective fining agent but over-fining can strip wine of flavour and colour and leave it with an earthy flavour. Egg white (albumen) is another popular choice for red wines as it has an additional affect of softening the tannins. Carbon (in the form of activated charcoal) is often used to remove off-colours and off-odours from wine. It is quite harsh and is not generally used as a typical fining agent, but rather for wines with significant problems. Casein (protein derived from milk), gelatine (an animal protein), isinglass (obtained from the swim bladders of fish), Kieselsol (silicon dioxide) and PVPP (poly-vinyl-poly-pyrrolidone) are other examples of agents, with varying specific uses to solve specific problems. Companies like Laffort are constantly researching alternative and improved fining agents, producing new products such as Vegecoll (a potato-derived protein) to clarify and stabilise wines.

A last note on fining agents is on the suitability of wines treated with various types of agents for vegetarians, vegans and people with food allergies. For most wine drinkers, the type of fining agent used is irrelevant as it is almost completely removed from the wine itself. After fining, clarification and stabilisation, wines are often filtered to remove the last possible particles and insoluble matter left. Trace amounts of fining agents (trace meaning on the absolute limit of detection – micro- or nanograms per litre) may remain in the wine and people with severely sensitive allergies may be affected. Strict vegans and vegetarians will also avoid wines who use animal-derived proteins (such as casein and albumen) as fining agents. VeganSA has a list of wine estates who produce vegan wines by using only non-animal derived fining agents.

The regulation around fining agents still seems a bit fuzzy. Declaring potential allergens on wine labels has become mostly standard practice, worldwide. Canada and the OIV (Organisation Internationale de la Vigne et du Vin) have recommended guidelines in place and some countries may be held to certain labelling practices when exporting wine. The general consensus seems to be that potential allergens should be listed, but many argue that if the filtering process efficiently removes these agents, listing them as additives on the labels may not be entirely accurate. It becomes even more confusing, as Europe applies “truth in labelling” law, the implication being if the label states eg. “Contains milk” (referring to casein) but the filtering process has removed all traces of casein, the winery is essentially breaking the law. This means a “better safe than sorry” approach isn’t really viable either.

Bottom line: don’t be afraid of fine(d) wines. The process may sound a bit strange (having made wine myself, I still find it counterintuitive to add a bucket of clay slush or some whipped egg whites to a tank of wine) but it’s all very scientific and the end result is healthy wines, with longevity and a crystal clear hue, making our favourite drink even more appealing.

For a more technical piece on the science behind fining, I recommend this Wineland technical post. You can also read more about the industry regulations and general good practice around fining agents and allergens in wine by checking out the SAWIS page and searching for the keyword “fining”.  


3 comments on “On Fining Agents and Clarity

  1. wi3sa

    Hmm… does the overuse of clay them sometimes add to “earthy flavours” present in some wines?

    But I never actually read the labels for ingredients on wine bottles… dumb me assumed “grapes” – I’m going blegh right about now.

    1. Marthélize Tredoux Post author

      Some of the practical winemaking sources I found online suggests the overuse of bentonite (clay) might add an earthy flavour, but not as a positive attribute.

      It’s important to note that fining agents aren’t ingredients. The only “ingredient” at the beginning and the end of the winemaking process is still just grapes (or rather, grape juice – though fermented). The reason for listing organic (so animal or plant-derived as opposed to mineral) fining agents under the “May contain” on the label is mainly to warn people with severe and sensitive food allergies so they can avoid any dangerous triggers and to inform vegan and vegetarian wine drinkers so they can choose wines to suit their lifestyle.

      For example, you won’t see “Clay” listed on a wine label, or “Yeast” as they are removed. You also won’t see any of non-organic (mineral) fining agents, but egg, milk and other protein derivates will likely be named.

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