Ever wondered what wine sediment is and how it is formed? Why do some wines have sediment and others do not? Is wine sediment a health hazard?
When people talk about sediment, they probably refer to the dregs which settle at the bottom of the wine bottle. However, in its broadest sense, sediment is the solid material that sits on the bottom of any wine container, such as a bottle, vat, tank, cask, or barrel. Sediment is a characteristic of both red and white wines. It is a highly heterogeneous mixture which, at the start of wine-making, consists primarily of dead yeast cells, fragments of grape pulp and skin, and the seeds that settle out of new wine.
Simply put, sediment can form naturally in wine both during the fermentation process and also while maturing in a bottle. In typical red winemaking, crushed grapes and their juices are fermented together, while white wines are usually made from the juice of the grapes only. The presence of solids is where most sediment comes from. It follows that whites will have less sediment than red wines in the end.
The initial sediment which is formed in wine appears during the fermentation process and is called “lees”. These lees (slurry) take the form of solid matter that settles at the bottom of the fermentation tanks. Following fermentation, wine is racked (transferred to another container) a few times during processing. In most cases of wine processing, the solids such as yeast cells, pulp, tartrate crystals, fining particles, proteins and tannins are removed or filtered during the transfer from fermentation tanks to aging tanks. Clarification can occur quickly or very slowly, depending on what the wine maker is trying to achieve. The more a wine is left in contact with the lees sediment at each stage, the more character and complexity (depending on the variety of grapes) it will acquire.
In order to get rid of all left over particles in the wine, we often need to add a chemical that can bond with the particles, making them heavy enough to sink. There are many methods to choose from and many different fining agents are used to clear a wine from sediment. Aside from chemicals, the wine can be clarified if passed through filtration as well. It takes a special filter that is fine enough to catch stray yeast cells and other microbial organisms. The drawback to this method is that the filter can remove sediment as well as precious flavours, a rather undesirable result.
The next step in winemaking involves stabilization. By unstable we mean that the wine is susceptible to spoilage. The most common causes of spoilage are oxidation, unintentional second fermentations, and excess protein. There are different stabilization methods for different types of potential spoilage and several chemicals can be used to improve wine stability.
Crystal clear wines, like most of what lands on store shelves, are the result of complex fining and filtering processes, and the chemicals used to achieve this end are frequently the subject of wine additive debates. Traditionally, egg whites are used in the fining process of wine because the particles clump onto the albumen and sink to the bottom of barrels or tanks. Other examples include sulphur-dioxide which is used to kill off yeast cells, fermentation enzymes which help prevent a pectin haze from forming so that the wine is easier to clear, and bentonite which is used to remove excess protein.
Grapes contain small quantities of protein which are carried over into the wine during fermentation. Originally, the protein molecules are much too small to be visible in the wine. However under certain conditions, protein molecules link together (polymerize) and grow larger until the particles are too bulky to remain suspended in the wine. Winemakers call protein haze “hot instability” because warm storage conditions trigger the phenomena. Excess protein seldom causes stability problems in red wines. However, white and blush wines must undergo a special treatment to remove the excess proteins that will cause a haze to develop if the wine is subjected to hot temperatures over time.
Another important process associated with preventing potential wine spoilage and sediment formation is cold stabilization. During this process the wine temperature is reduced to almost freezing point to purposefully form tartrate crystals that can then be removed through racking. These harmless crystals are formed when tartaric acid precipitates out of the wine. Their presence has no effect on the flavour, but they can put people off because they look like minute pieces of broken glass. Wine enjoyment is strongly influenced by first impressions, and most people form their first impression about the wine visually. Consequently, clarity and stability are extremely important. Practically all wines can be clarified, stabilized and prepared for bottling using appropriate filtration methods and standard winemaking practices including cooling the wine to cold temperatures and fining the wine with suitable materials.
Once the wine is bottled there are typically two types of sediments that may appear in bottled red wine: colloids and tartrates. The smaller, grainier types are colloids of pigment, polysaccharides, and protein. The longer the wine ages, the more chance that these substances may come together and eventually form particles which will fall to the bottom of the bottle. What we are experiencing is the precipitation over time of all sorts of complex tannins and coloured compounds. The exact composition of these materials is not known, but it is most likely a mixture of tannin and protein. Sediment is more common in red wines of moderate phenolic content that have not been aged in oak.
In the case of white wine, the causes of cloudiness in bottles wine is rare but could be attributed to protein coagulation, polyphenol colloids precipitation, metal haze and tartrate crystallization. This phenomenon can be prevented if care is taken during the various stages of wine production. Firstly, after crushing grapes and before fermentation, the juice is left to settle for about 48 hours, therefore allowing the separation of liquid from the solids. When fermentation is completed, the first rack is carried out in order to remove any slurry that has sunk to the bottom of the tank. Subsequently, additional racking is carried out by the wine maker in order to eliminate unwanted sediments. The final clarification is achieved with the help of cold stabilization and filtering before bottling.
Sedimentation within the bottle is a natural occurrence in many red wines, generally those designed to withstand some aging, and it simply reflects the solid matter settling out of the wine. The best way to remove wine sediment in a bottle is with a decanter. If you’re serving a red wine that’s been aging for several years, you’ll want to hold it up to the light to see if a sediment has formed. If so, stand the wine bottle upright for a few days before serving so that all the sediment collects in the small area at the bottom of the bottle. Sediment can be filtered out by slowly pouring the wine from its existing bottle into a decanter, being careful to leave the crystals and the last of the wine in the bottle. Decant it slowly, with the neck of the bottle near a light source and stop pouring the moment you see any sign of sediment in the neck.
The main thing to note is that sediment is not a fault. In most cases it may even be considered as a good sign, one which indicates a fine wine that was treated with minimal processing. Some claim that un-fined and unfiltered wines taste more honest and more interesting, all things considered.
It is a fact that many consumers are upset by seeing these crystals in white wine and return them to the retailer. Consequently, most mass wine producers process the wine to precipitate and filter out all potential sediments which does, of course, result in a less complex and less interesting wine. Sediment may not look pretty in your wine glass, but do not let it slow you down! The wine is still perfectly safe to drink. Ultimately, when people taste wines, they’re looking for something in particular, whether it be a sweetness, a bitterness, an aroma or even simple alcohol. In the end, the winemaking process yields a great variety of flavours enjoyed by many, once people get an idea of what they’re looking for.
Wine, when made well, is a natural product and should be appreciated as such. Remember, most sediments are completely natural and harmless if consumed. The best way to avoid them is to pour slowly so the sediments catch in the shoulder of the bottle, which can be done either into a decanter or directly into the glass. As long as the wine is stored properly, it should give you delight when you get around to drinking it.
So don’t stress over a little sediment. Just enjoy your glass of wine.