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: https://www.ttb.gov/faqs/allergen-labeling.

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

Sources:

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

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

We all love to see beautiful vineyards at harvest – green, full vines with abundant clusters of red or green grapes. Harvest is an exciting time as the vines bring forth their bounty and then take a deep sigh of relief. Following harvest, the vines decorate the landscape with vibrant hues of yellow and orange. But sadly, the vines then give up their leaves to become brown, bare twigs in the ground by winter. But are these vines really as lifeless as they appear? Contrary to their appearance, these vines have prepared themselves to survive and thrive during the cold winter months.

To understand the winter dormancy period, we first need to understand the annual growth cycle of the vine.

Budburst – March-April in Northern Hemisphere (September-October in Southern Hemisphere).

As temperatures begin to exceed 50^oF, buds begin to swell and burst open to later become new shoots. Some grape varietals experience bud burst earlier or later than other varietals. Frost at this time can significantly damage these buds and the following early shoots. It is interesting to know that buds will form for the current year’s crop, and also for the following year’s crops (remaining dormant until the following year).

Early Shoot and Leaf Growth – March-April in Northern Hemisphere (September-November in Southern Hemisphere.  Shoots develop and begin a period of rapid growth, spawning budding leaves and tendrils. Until leaves mature and can support photosynthesis, this growth is fueled by carbohydrates that have been stored in the woody vines and roots following harvest. Green leaves begin to fully develop as shoots mature to reach the flowering stage.

Flowering and Fruit Set – May-June in Northern Hemisphere (November-December in Southern Hemisphere)

Depending on temperatures, about 40-80 days after budbreak, flower clusters will begin to appear on the end of the shoots. Most cultivated grape vines are “hermaphroditic” containing both male stamens (pollen) and female ovaries (seeds). With a few weeks of some warm sunshine, flowers grow and lose their protective “cap”, leading to “fertilization” with the next gentle breeze. Unfertilized flowers will fall to the ground, sadly never to become a grape. This stage of the vine lifecycle is critical to development of a healthy crop yield and can be damaged by cold, harsh and rainy weather.

Véraison and Berry Ripening – July-September in Northern Hemisphere (January-March in Southern Hemisphere)

After fruit set, both white and red grapes are hard green berries that are low in sugar and high in acid. These berries continue to grow in size for the next 40-60 days followed by “véraison.” This is the time that berries begin to soften and change color, becoming red, purple, black, or a more translucent, golden green. Warm, sunny weather is needed at this time for the grapes to ripen and accumulate sugars.

Harvest – September-October in Northern Hemisphere (March-April in Southern Hemisphere)

Grapes have reached their peak ripeness: sugars and pH have increased, while acids (such as malic) begin to decline. Tannins and other grape phenolics have matured, giving rise to enticing aromas and flavors. Grape clusters are removed from the vines to begin their journey into becoming wine.

After harvest, leaves remain on the vine where they continue to perform photosynthesis and produce carbohydrate reserves. Eventually, the vines begin to pull back these carbohydrates from the leaves to later be stored, causing the leaves to turn brilliant shades of yellow, orange, and eventually brown. Be aware that red leaves on the vines are not a typical harvest color and often indicate the presence of vine disease.

Now that vines are no longer spending energy producing fruit, their energy can now be spent in their root system. Many new small roots begin to grow and seek out vital nutrients in the soil in a process known as “root flush.”

Winter Dormancy – December-March in Northern Hemisphere (July-September in Southern Hemisphere)

By winter, vines have stored their nutrient and carbohydrate reserves in the cordons, woody trunk and roots. These reserves are critical so that the vines have energy to produce budburst and new shoots in spring – a time when there are not yet leaves on the vine to produce carbohydrates via photosynthesis. Also important is that vines have gone through a dehydration process so that water does not freeze within the vine and root tissues during the cold winter months. Damaging cold winter frosts are not a typical problem in California growing regions – but can be a serious problem in many colder regions.

However, this cold “winter dormancy” is vital to the growth cycle of vines. Temperatures must become cold enough that the above ground vine growth will halt. This cold resting period is necessary to ensure normal budburst and growth cycle in the spring.

Winter dormancy is also the time for winter pruning to be performed. This pruning sets the stage for the next years growing cycle. Woody canes from the previous year’s growth are cut off and new canes are selected from which the new shoots will grow come springtime. This pruning also stimulates the vines so that when warmer weather and sunshine arrive, the vines awaken to a new growth cycle.

So, next time you pass a dormant field full of bare, woody vines, just know that the vines are preparing themselves to greet the spring sunshine with a burst of new growth and start making grapes for your next great bottle of wine.

Irene Scott, WSET-3 – Wine Education Chair

References:

Wine and Spirit Education Trust, 2016. Understanding wines: Explaining style and quality. wsetglobal.com, London, UK.

Urska (2018, Dec. 5). Grapevines During Winter Dormancy, Evineyardapp.com.

Burgess, Laura (2016, Jan. 29). Below the Surface: Winter in the Vineyard, Vinepair.com.