Wine Education 101: Blood, Guts, Bones and Mud in our Wine?

You might think that wine, a product made from grapes, should be “vegan” – not containing any animal products.  This is not necessarily the case for many of our wines today.  In winemaking, there is a process where the wine needs to settle and clarify so that ultimately the bottle of wine that we open is clear of sediment and haze.  Left on its own to occur naturally, this process could take up to a year to settle and produce a clear wine.  Further fining might also need to be performed to remove undesirable constituents such as excessive astringency or bitterness.  In order to accomplish this settling and fining of wines more efficiently, winemakers may use a variety of additives to speed up and enhance this process.  So, could there really be blood, guts, bones and mud in our wine?

The process of “fining” utilizes a substance (often a protein) that is mixed into the wine barrels or tanks.  The substance is attracted to small, suspended particles in the wine that could make the wine cloudy or hazy.  These larger, combined molecules will then precipitate (fall) to the bottom of the wine barrel or tank.  The “fined” wine is then removed from the top.  In theory, there should be little to none of the fining agent left in the “fined” wine. But what fining agents could possibly be left behind in that bright, clear bottle of wine?

In days past, a traditional fining agent used in winemaking was ox blood.  This was added to wine (as a liquid or in dried form) and was a very effective fining agent.  However, in 1997 both the EU and the US banned its use when the mad cow disease scare peaked.  Because of export restrictions of any wine containing blood, there is not much chance that your 25-year old bottle of Bordeaux wine you were saving contains any fining blood.

An effective fining agent used today is isinglass – something you may think of as “fish guts”.  Isinglass is made from the air bladders of fish – usually sturgeons.  It is an excellent fining agent for clarification and removal of bitterness and astringency in white wines.  While the correct use of isinglass can help unmask fruit character, over-use can impart your wine with a “fishy” aroma.

Another non-vegan fining product used in wine is gelatin. Gelatin is a protein made from boiled skin, tendons, ligaments, and/or bones (hooves) with water.  Gelatin is an aggressive protein fining agent that is primarily used to soften red wines by reducing tannins and astringency. Over-use of gelatin fining could result in color loss in red wine and protein instability.

Bentonite is probably the most commonly used fining agent for the clarification and protein stabilization of wine.  However, since it can also remove color, it is more often used in white wine.  Bentonite used in the U.S. is made from clay that is found in Wyoming (sodium bentonite); in Europe, Bentonite is made from clay found in South Africa (calcium bentonite). When Bentonite is dry, it is hard and water-tight; when wet, it is slimy and slick.  Other uses for Bentonite include lubricating oil drill bits; an additive to animal feed (it swells and slows down digestion); used to treat diarrhea; is the mud in “mud baths” and in “mud wrestling”; used in fabric softeners (for ion exchange/water softening).  Bentonite is a very multi-purpose wine fining agent!

A very traditional fining agent for red wine is egg whites, or Albumin (made from chicken egg whites).  This fining agent helps to remove astringency and bitterness and is a good general finishing “polish” for red wines.  Egg whites are not as effective in white wine as it needs the presence of tannins to flocculate.  While the egg whites flocculate with tannins and precipitate to the bottom of the barrel/tank to be later racked off, those with an allergy to eggs might still have reason to be concerned.

Another fining agent that has potential allergy concerns is Casein (potassium caseinate) – the principal protein in milk. Today, Casein is mostly used in its purified form, but skim milk was used in the past and still may be in use today.  Casein is a very gentle fining agent and works well in removing over-oaked aromas, oxidized aromas and browning in white wines.

There are many more products in the winemakers fining “toolkit” today including mineral compounds, polysaccharides (such as chitin found in the covering layer of insects and in the cell walls of fungi), and synthetic polymers (plastics like PVPP).  Most of the products used for fining will precipitate to be bottom of the tank/barrel and be racked off – leaving little or no presence behind in the finished wine.  It is possible that you may find “un-fined” wine – but this can be challenging as even the most traditional Bordeaux wine regions commonly use fining.

Currently, the Alcohol and Tobacco Tax and Trade Bureau (TTB) does not require the disclosure of major allergens on wine labels.  However, there is a current proposal to make labelling of major food allergens on alcohol labels mandatory.  To read more about this, visit:

So, perhaps you may have a greater appreciation (or more disgust) for what it takes to make that finished bottle of wine clear and free of sediments and haze.  Cheers!

Irene Scott, WSET-3 – Wine Education Chair


Wann, Grady, “Fining and Stability”, UC Davis Extension, 2020.

Jackson, R.S., Wine Science: Principles and Applications, Academic Press, 2014